I read the article and think of colour polmorphism evolution rather than speciation. But as everyboyd has said the results are interesting and the study was well set.
Hastings
VIEWS FROM THE SCIENTIST
Capturing the eye of a potential mate is the first step in propagating a species. But can the way a female sees males of a certain color lead a single species of fish to split into two? A study published this week in Nature suggests two species of cichlid fish -- one red and one blue -- may have arisen from the female mating preference for males she is best able to see. "We've wanted since Darwin to understand how species originate," said Karen Carleton, a biologist at the University of Maryland and co-author of the study. "This is one of first times we've been able to understand from the molecular level to the fish to the environment to get the whole picture." Researchers have long believed that geographic isolation was the primary force behind the evolution of a single species into two reproductively incompatible groups, yet, as lead author and evolutionary biologist Ole Seehausen, found in Lake Victoria in eastern Africa, the red and blue cichlids were separated by as little as 15 meters of water. Earlier studies showed that red cichlids live closer to the lake bottom, while the blue cichlids frequent more shallow waters, and the females (dressed in muted yellow fins) chose the most vibrantly colored of the males at their water depth. To understand factors driving female mating preference, Seehausen's team examined light gradients in different depths of water and the opsin gene, which produces a protein that detects color. "We knew about the mating preferences [in cichlids] but we did not know where in the process the divergent evolution at the opsin gene locus occurred," Seehausen said. The researchers genotyped the opsin gene of cichlids from five islands in Lake Victoria and identified the gene's variants in the red and blue cichlids. They then expressed the genes in vitro, showing that the protein product of each variant absorbed light at a different wavelength: in red cichlids, the protein was more sensitive to red light, while in blue cichlids it was more sensitive to blue light. Meanwhile, light gradient data showed blue light was more easily visible in shallow water and red light in deep water. The findings suggest that natural selection in each species' visual system toward red- or blue- sensitivity, which allows cichlids to best navigate their environment, may also drive females to the males they are best able to see. "The evidence shows that in a heterogeneous environment, where different conditions prevail along a gradient, selection is strong enough to create two species," said Seehausen. Trevor Price, who studies the evolution of color patterns in birds at the University of Chicago, said he's excited about Seehausen's model, but stressed that more evidence is needed to "make the connection that female color vision is driving speciation." Females with the red-biased and blue-biased opsin variants generated from controlled crosses in Seehausen's lab demonstrated no preference between red and blue males in the lab tank. "These findings suggests the opsin gene themselves are not causing mating preference," Seehausen said. "It could be the interaction of visual gene and ambient lighting." Seehausen said his group plans to look for additional genes and traits involved in mate choice in cichlids in order to understand how these interact with the adaptation of the visual system.
Thursday, October 30, 2008
Tuesday, October 7, 2008
THE HUMAN DIVERSITY MAY BE COMING TO A HALT
Hi
Here is another mind blowing article on the componets that determine the human
diversity and indeed all living creatures on our planet earth.
The people on the driving seat are warning that,while these processes may be still at
work in other organism just like our super radiation of Lake Malawi cichlid fish, the story
is different in human populations.
However, as we live in an ever changing universe the story may not be as simple as we
may see it. In mind is the global warming issue. With most of the areas on earth
claimed to be at risk, the human population may be heading for a revolution of
their diversity in the near or distant future. The effective population size might
be at risk and random drift will play its part, thus reshuffling the diversity as
well.
All in all its intersting and informative to know how our diversity is struggling at
the moment.
Have a good time read on the article below.
Hastings
========
Press Assoc. - Tuesday, October 7 04:21 am
Human evolution is grinding to a halt, according to a leading genetics expert.
The gloomy message from Professor Steve Jones is: this is as good as it gets.
Prof Jones, from the Department of Genetics, Evolution and Environment at University College London, believes the mechanisms of evolution are winding down in the human race.
At least in the developed world, humans are now as close to utopia as they are ever likely to be, he argues. Speaking at a UCL Lunch Hour Lecture in London, Prof Jones said there were three components to evolution - natural selection, mutation and random change.
He said: "In ancient times half our children would have died by the age of twenty. Now, in the Western world, 98% of them are surviving to the age of 21. Our life expectancy is now so good that eliminating all accidents and infectious diseases would only raise it by a further two years. Natural selection no longer has death as a handy tool."
Mutation rate was also slowing down, he said. Although chemicals and radioactive pollution could cause genetic changes, one of the most important mutation triggers was advanced age in men. "Perhaps surprisingly, the age of reproduction has gone down - the mean age of male reproduction means that most conceive no children after the age of 35," said Prof Jones. "Fewer older fathers means that if anything, mutation is going down."
Random alterations to the human genetic blueprint were also less likely in a world that had become an ethnic melting pot, according to Prof Jones.
He said: "Humans are 10,000 times more common than we should be, according to the rules of the animal kingdom, and we have agriculture to thank for that. Without farming, the world population would probably have reached half a million by now - about the size of the population of Glasgow.
"Small populations which are isolated can change - evolve - at random as genes are accidentally lost. Worldwide, all populations are becoming connected and the opportunity for random change is dwindling. History is made in bed, but nowadays the beds are getting closer together. Almost everywhere, inbreeding is becoming less common. In Britain, one marriage in fifty or so is between members of a different ethnic group, and the country is one of the most sexually open in the world. We are mixing into a global mass, and the future is brown."
He added: "So, if you are worried about what utopia is going to be like, don't; at least in the developed world, and at least for the time being, you are living in it now."
Here is another mind blowing article on the componets that determine the human
diversity and indeed all living creatures on our planet earth.
The people on the driving seat are warning that,while these processes may be still at
work in other organism just like our super radiation of Lake Malawi cichlid fish, the story
is different in human populations.
However, as we live in an ever changing universe the story may not be as simple as we
may see it. In mind is the global warming issue. With most of the areas on earth
claimed to be at risk, the human population may be heading for a revolution of
their diversity in the near or distant future. The effective population size might
be at risk and random drift will play its part, thus reshuffling the diversity as
well.
All in all its intersting and informative to know how our diversity is struggling at
the moment.
Have a good time read on the article below.
Hastings
========
Press Assoc. - Tuesday, October 7 04:21 am
Human evolution is grinding to a halt, according to a leading genetics expert.
The gloomy message from Professor Steve Jones is: this is as good as it gets.
Prof Jones, from the Department of Genetics, Evolution and Environment at University College London, believes the mechanisms of evolution are winding down in the human race.
At least in the developed world, humans are now as close to utopia as they are ever likely to be, he argues. Speaking at a UCL Lunch Hour Lecture in London, Prof Jones said there were three components to evolution - natural selection, mutation and random change.
He said: "In ancient times half our children would have died by the age of twenty. Now, in the Western world, 98% of them are surviving to the age of 21. Our life expectancy is now so good that eliminating all accidents and infectious diseases would only raise it by a further two years. Natural selection no longer has death as a handy tool."
Mutation rate was also slowing down, he said. Although chemicals and radioactive pollution could cause genetic changes, one of the most important mutation triggers was advanced age in men. "Perhaps surprisingly, the age of reproduction has gone down - the mean age of male reproduction means that most conceive no children after the age of 35," said Prof Jones. "Fewer older fathers means that if anything, mutation is going down."
Random alterations to the human genetic blueprint were also less likely in a world that had become an ethnic melting pot, according to Prof Jones.
He said: "Humans are 10,000 times more common than we should be, according to the rules of the animal kingdom, and we have agriculture to thank for that. Without farming, the world population would probably have reached half a million by now - about the size of the population of Glasgow.
"Small populations which are isolated can change - evolve - at random as genes are accidentally lost. Worldwide, all populations are becoming connected and the opportunity for random change is dwindling. History is made in bed, but nowadays the beds are getting closer together. Almost everywhere, inbreeding is becoming less common. In Britain, one marriage in fifty or so is between members of a different ethnic group, and the country is one of the most sexually open in the world. We are mixing into a global mass, and the future is brown."
He added: "So, if you are worried about what utopia is going to be like, don't; at least in the developed world, and at least for the time being, you are living in it now."
Tuesday, September 30, 2008
Conservation Of Freshwater Fish Biodiversity: A Challenge For The Countries Of The South
ScienceDaily (Mar. 27, 2008) — Scientists at the Institut de Recherche Pour le Développement (IRD) and colleagues* have made the first global-scale analysis of the processes leading to freshwater fish invasion in river basins. This phenomenon affects most river ecosystems of countries of the Northern hemisphere. However, in the context of economic growth developing countries are now experiencing, their river basins, home to the greater part of freshwater fish biodiversity, are at risk of the same fate unless vigilance is applied.
Humans have regularly been introducing exotic species into natural environments in order to provide for their nutritional necessities or meet less indispensable purposes such as horticulture, fishing or hunting. However, the particular environments are not always adapted for hosting new arrivals. Past introduction attempts, such as that of wild rabbit into Australia or brown fario trout into Southern hemisphere water courses, led to an awareness that these different species, qualified by scientists as none-native, have the power to upset an ecosystem.
The 2002 Convention on Biodiversity recognized that the species introductions can cause regression of biological diversity, following destruction of natural habitats. Although it has long seemed likely that human activity plays a major role in such effects, no scientific study had yet yielded measurements of its involvement at planetary scale for a given group of species. An international research team comprising IRD, CNRS and University of Toulouse scientists recently published a study that gave the first real demonstration that human activity is the main driving factor behind the establishment of exotic fish species populations in river ecosystems.
Examination of data on presence of around 10,000 freshwater fish in 1055 river basins covering both 80% immersed lands and 80% of globally recorded freshwater fish species allowed identification of seven species-invasion hot-spots: the Pacific coast of North America and Central America, Patagonia, southern and western Europe, South Africa and Madagascar, central Asia, the South of Australia and New Zealand. These regions are characterized by river basins where non-native species make up more than one quarter of the freshwater fish species recorded. Moreover, they are superimposed on biodiversity hot-spots which correspond to geographical zones a strong endemism rate and a very high total number of species.
The team also sought to determine the extent of the relative influence of the particular characteristics of each ecosystem and human activities on the diversity of the non-native fish species. Three hypotheses were tested: the "biotic resistance", "biotic acceptance" and "human activity". The first suggests that a high diversity of freshwater fish in the host ecosystem acts as a barrier to the establishment of non-native fish specie populations.
The second postulates conversely that, for a given ecosystem, non-native species diversity follows that of native species because favourable ecological conditions for the latter are also suitable for the newly arrived species. As for the third, it takes account of the different indicators at river-basin scale (gross domestic product, percentage of land urbanized, population density), that can yield determination of the relation between anthropic pressure and non-native species diversity.
The three hypotheses' relative weight was measured using statistical methods. For the whole set of river basins investigated, the environmental conditions of fluvial ecosystems were found to have practically no influence on the exotic species diversity. On the contrary, it is the human factors, and especially the intensity of economic activities --measured by the GDP, which determine the number of non-native species present in a river basin.
These results thus suggest that the economic development foreseen in the developing countries should be accompanied by a rise in the number of non-native freshwater fish species. Given that biological invasions are considered as one of the main causes of biodiversity loss, such a scenario would probably be detrimental to the aquatic biodiversity conservation of these regions. This study indicates that exceptional river ecosystems, like the Amazon Basin in South America or that of the Congo in central Africa, are still hardly affected by species introduction.
For example, no more than 1% of the 3000 species of fish recorded in the River Amazon are non-native species. Just as a considerable number of countries of the South are seeing their economic growth take off, this kind of study should be useful in the future for setting up an effective watch system for the surveillance of the exotic species colonizing the most biodiversity-rich natural environments and make it possible to apply the principle of precaution before they become invasive.
*This research was conducted in conjunction with scientists from the 'Groupe de recherche sur la gestion des écosystèmes' of Antwerp University (Belgium) and the Centre Interniversitaire de Recherche sur le Saumon atlantique (CIRSA) of Laval University (Canada)
Humans have regularly been introducing exotic species into natural environments in order to provide for their nutritional necessities or meet less indispensable purposes such as horticulture, fishing or hunting. However, the particular environments are not always adapted for hosting new arrivals. Past introduction attempts, such as that of wild rabbit into Australia or brown fario trout into Southern hemisphere water courses, led to an awareness that these different species, qualified by scientists as none-native, have the power to upset an ecosystem.
The 2002 Convention on Biodiversity recognized that the species introductions can cause regression of biological diversity, following destruction of natural habitats. Although it has long seemed likely that human activity plays a major role in such effects, no scientific study had yet yielded measurements of its involvement at planetary scale for a given group of species. An international research team comprising IRD, CNRS and University of Toulouse scientists recently published a study that gave the first real demonstration that human activity is the main driving factor behind the establishment of exotic fish species populations in river ecosystems.
Examination of data on presence of around 10,000 freshwater fish in 1055 river basins covering both 80% immersed lands and 80% of globally recorded freshwater fish species allowed identification of seven species-invasion hot-spots: the Pacific coast of North America and Central America, Patagonia, southern and western Europe, South Africa and Madagascar, central Asia, the South of Australia and New Zealand. These regions are characterized by river basins where non-native species make up more than one quarter of the freshwater fish species recorded. Moreover, they are superimposed on biodiversity hot-spots which correspond to geographical zones a strong endemism rate and a very high total number of species.
The team also sought to determine the extent of the relative influence of the particular characteristics of each ecosystem and human activities on the diversity of the non-native fish species. Three hypotheses were tested: the "biotic resistance", "biotic acceptance" and "human activity". The first suggests that a high diversity of freshwater fish in the host ecosystem acts as a barrier to the establishment of non-native fish specie populations.
The second postulates conversely that, for a given ecosystem, non-native species diversity follows that of native species because favourable ecological conditions for the latter are also suitable for the newly arrived species. As for the third, it takes account of the different indicators at river-basin scale (gross domestic product, percentage of land urbanized, population density), that can yield determination of the relation between anthropic pressure and non-native species diversity.
The three hypotheses' relative weight was measured using statistical methods. For the whole set of river basins investigated, the environmental conditions of fluvial ecosystems were found to have practically no influence on the exotic species diversity. On the contrary, it is the human factors, and especially the intensity of economic activities --measured by the GDP, which determine the number of non-native species present in a river basin.
These results thus suggest that the economic development foreseen in the developing countries should be accompanied by a rise in the number of non-native freshwater fish species. Given that biological invasions are considered as one of the main causes of biodiversity loss, such a scenario would probably be detrimental to the aquatic biodiversity conservation of these regions. This study indicates that exceptional river ecosystems, like the Amazon Basin in South America or that of the Congo in central Africa, are still hardly affected by species introduction.
For example, no more than 1% of the 3000 species of fish recorded in the River Amazon are non-native species. Just as a considerable number of countries of the South are seeing their economic growth take off, this kind of study should be useful in the future for setting up an effective watch system for the surveillance of the exotic species colonizing the most biodiversity-rich natural environments and make it possible to apply the principle of precaution before they become invasive.
*This research was conducted in conjunction with scientists from the 'Groupe de recherche sur la gestion des écosystèmes' of Antwerp University (Belgium) and the Centre Interniversitaire de Recherche sur le Saumon atlantique (CIRSA) of Laval University (Canada)
Freshwater Fish Invasions The Result Of Human Activity
ScienceDaily (Feb. 9, 2008) — Globally, invasive species represent a major threat to native species. A new paper* shows that, for rivers and lakes, where these invasions occur is predicted by human activity; find an area where economic activity is high and, in nearby lakes and rivers, up to a quarter of species will be migrants to the region.
In the first global analysis of invasions in aquatic habitats, Fabien Leprieur, Olivier Beauchard, and colleagues investigate what factors can predict invasion events and find that human activity is to blame.
Prior to this work, ecologists have debated the relative importance of human activity and intrinsic features of an ecosystem when trying to explain the distribution of invasive species. Researchers have suggested that the number of native species would predict the number of invasive species settling in an area.
This is because either an environment that is good for fish generally, and therefore hosts lots of natives, would be good for invaders too; or, conversely, because an environment that was host to many natives would be"full" to hopeful migrants.
Leprieur and colleagues from France, Belgium, and Canada investigated the fish species found in over 1000 river basins and found that the number of native species does not correlate with the number of invasive species.
Instead, they found that invasion was related to gross domestic product, with higher human population density, and with nearby urbanized land. This raises serious concerns for the future of many aquatic ecosystems as the rate of global economic expansion continues to rise, predicting an increase in invasive species and, with it, an increase in the extinction of native animals.
*Citation: Leprieur F, Beauchard O, Blanchet S, Oberdorff T, Brosse S (2008) Fish invasions in the world's river systems: When natural processes are blurred by human activities. PLoS Biol 6(2): e28. doi:10.1371/journal.pbio.0060028
In the first global analysis of invasions in aquatic habitats, Fabien Leprieur, Olivier Beauchard, and colleagues investigate what factors can predict invasion events and find that human activity is to blame.
Prior to this work, ecologists have debated the relative importance of human activity and intrinsic features of an ecosystem when trying to explain the distribution of invasive species. Researchers have suggested that the number of native species would predict the number of invasive species settling in an area.
This is because either an environment that is good for fish generally, and therefore hosts lots of natives, would be good for invaders too; or, conversely, because an environment that was host to many natives would be"full" to hopeful migrants.
Leprieur and colleagues from France, Belgium, and Canada investigated the fish species found in over 1000 river basins and found that the number of native species does not correlate with the number of invasive species.
Instead, they found that invasion was related to gross domestic product, with higher human population density, and with nearby urbanized land. This raises serious concerns for the future of many aquatic ecosystems as the rate of global economic expansion continues to rise, predicting an increase in invasive species and, with it, an increase in the extinction of native animals.
*Citation: Leprieur F, Beauchard O, Blanchet S, Oberdorff T, Brosse S (2008) Fish invasions in the world's river systems: When natural processes are blurred by human activities. PLoS Biol 6(2): e28. doi:10.1371/journal.pbio.0060028
Thursday, August 14, 2008
LAKE MALAWI FIELD TRIP
Just come back from Lake Malawi field trip, with a lot of Cynotilapia afra collections.
The populations from Ngara to Cape Maclear, all is being tested for reproductive isolation,
hybridization and genetic diversity.
This will keep me busy until, July 09.
Watch this space for early results of my findings and impact on fish diversity,
within Lake Malawi.
A picture is Otter Point boulder, a usual dwelling place for our favourite mbuna cichlids.
Hastings
Tuesday, March 25, 2008
Evolution Of New Species Slows Down As Number Of Competitors Increases
ScienceDaily (Mar. 25, 2008) — The rate at which new species are formed in a group of closely related animals decreases as the total number of different species in that group goes up, according to new research.
The research team believes these findings suggest that new species appear less and less as the number of species in a region approaches the maximum number that it can support.
In order for new species to thrive, they need to evolve to occupy their own niche in the ecosystem, relying on certain foods and habitats for survival that are sufficiently different from those of other closely related species.
Competition between closely related species for food and habitat becomes more intense the more species there are, and researchers believe this could be the reason for the drop-off in the appearance of new species over time.
Dr. Albert Phillimore, from Imperial College London's NERC Centre for Population Biology, lead author on the paper, explains: "The number of niches in any given region is finite, and our research supports the idea that the rate of speciation slows down as the number of niches begins to run out.
"In essence, it seems like increased competition between species could place limits on the number of species that evolve."
The new study used detailed analysis of the family trees, or phylogenies, of 45 different bird families. By examining the rate at which new species have arisen in each of these trees over a period of millions of years, scientists saw that the rate of appearance of new species seemed to be much higher in the early stages of the family tree, compared to more recent lower rates.
For example, when the researchers examined the phylogeny of tit birds they found that some 10 million years ago, species formed rapidly but this rate has slowed over time to perhaps a quarter of the initial rate.
Journal reference: Phillimore AB, Price TD (2008) Density-dependent cladogenesis in birds. PLoS Biol 6(3): e71. doi:10.1371/journal.pbio.0060071
The research team believes these findings suggest that new species appear less and less as the number of species in a region approaches the maximum number that it can support.
In order for new species to thrive, they need to evolve to occupy their own niche in the ecosystem, relying on certain foods and habitats for survival that are sufficiently different from those of other closely related species.
Competition between closely related species for food and habitat becomes more intense the more species there are, and researchers believe this could be the reason for the drop-off in the appearance of new species over time.
Dr. Albert Phillimore, from Imperial College London's NERC Centre for Population Biology, lead author on the paper, explains: "The number of niches in any given region is finite, and our research supports the idea that the rate of speciation slows down as the number of niches begins to run out.
"In essence, it seems like increased competition between species could place limits on the number of species that evolve."
The new study used detailed analysis of the family trees, or phylogenies, of 45 different bird families. By examining the rate at which new species have arisen in each of these trees over a period of millions of years, scientists saw that the rate of appearance of new species seemed to be much higher in the early stages of the family tree, compared to more recent lower rates.
For example, when the researchers examined the phylogeny of tit birds they found that some 10 million years ago, species formed rapidly but this rate has slowed over time to perhaps a quarter of the initial rate.
Journal reference: Phillimore AB, Price TD (2008) Density-dependent cladogenesis in birds. PLoS Biol 6(3): e71. doi:10.1371/journal.pbio.0060071
Study Suggests Humans Can Speed Evolution
ScienceDaily (Aug. 5, 2004) — Atlanta (August 4,2004) -- It’s no secret that life in the 21st century moves at a rapid pace. Human inventions such as the Internet, mobile phones and fiber optic cable have increased the speed of communication, making it possible for someone to be virtually in two places at once. But can humans speed up the rate of one of nature’s most basic and slowest processes, evolution? A study by J. Todd Streelman, new assistant professor of biology at the Georgia Institute of Technology suggests that humans may have sped up the evolutionary clock for one species of fish.
Cichlid fish are well known to biologists for their rapid rate of evolution. While it takes many animals thousands of years to form new species, the cichlids of Africa’s Lake Malawi are estimated to have formed 1,000 new species in only 500,000 years, lightning speed in evolutionary terms. In the 1960s a fish exporter may have unwittingly set the stage for an evolutionary explosion when he introduced individuals of the species Cynotilapia afra to Mitande Point on the lake’s Thumbi West Island. As of 1983, the species hadn’t budged from Mitande Point. But when Streelman, then at the University of New Hampshire, Durham, and colleagues went to the island in 2001, they found the fish had evolved into two genetically distinct varieties in less than 20 years. The study appears in the August 13 edition of Molecular Ecology.
“This is a great example of human-induced evolution in action,” said Streelman. “It adds to a growing list of cases, including introduced salmon, flies and plants, where human disturbance has set the stage for contemporary evolution on scales we’ve not witnessed before.”
The fish have evolved into two genetically distinct and differently colored populations, one on the north side of the island, the other on the south, said Streelman. Cichlid color patterns are important in mate selection, so these distinct markings may promote the evolution of new species.
Whether or not that happens and how long it will take is a question to which Streelman is eager to find the answer. “It could be that we'll have new species in another 20 years, although this depends on a number of factors. Either way, we have a wonderful opportunity to follow the evolutionary trajectory of these populations over time. We plan to return to the island next July to do further study,” he said. “Thumbi West will be a valuable place to work for years to come.”
Cichlid fish are well known to biologists for their rapid rate of evolution. While it takes many animals thousands of years to form new species, the cichlids of Africa’s Lake Malawi are estimated to have formed 1,000 new species in only 500,000 years, lightning speed in evolutionary terms. In the 1960s a fish exporter may have unwittingly set the stage for an evolutionary explosion when he introduced individuals of the species Cynotilapia afra to Mitande Point on the lake’s Thumbi West Island. As of 1983, the species hadn’t budged from Mitande Point. But when Streelman, then at the University of New Hampshire, Durham, and colleagues went to the island in 2001, they found the fish had evolved into two genetically distinct varieties in less than 20 years. The study appears in the August 13 edition of Molecular Ecology.
“This is a great example of human-induced evolution in action,” said Streelman. “It adds to a growing list of cases, including introduced salmon, flies and plants, where human disturbance has set the stage for contemporary evolution on scales we’ve not witnessed before.”
The fish have evolved into two genetically distinct and differently colored populations, one on the north side of the island, the other on the south, said Streelman. Cichlid color patterns are important in mate selection, so these distinct markings may promote the evolution of new species.
Whether or not that happens and how long it will take is a question to which Streelman is eager to find the answer. “It could be that we'll have new species in another 20 years, although this depends on a number of factors. Either way, we have a wonderful opportunity to follow the evolutionary trajectory of these populations over time. We plan to return to the island next July to do further study,” he said. “Thumbi West will be a valuable place to work for years to come.”
Choosy Females Make Colourful Males
ScienceDaily (May 12, 2006) — Female fish prefer brightly coloured males because they are easier to see and are in better shape concludes Dutch researcher Martine Maan following her study of fish speciation in the East African Lakes. Environmental variation subsequently leads to differences in preference and eventually to speciation.
Evolutionary theory predicts that species can diverge if different females choose different characteristics in males. Yet females often pay attention to traits that reveal something about the quality of a male. As a result, females are likely to share the same preferences. In Lake Victoria cichlid fish, Martine Maan found a solution for this paradox: in different species, different traits reveal male quality.
She examined two closely related species, one with blue males and the other with red males. Females prefer males of the right colour, blue or red, and within those categories they choose the most brightly coloured males. They do so for good reasons: brightly coloured males from both species carry fewer parasites and are thus in better condition. Moreover, both species are adapted to different infection risks, which are associated with a difference in water depth and food choice. It is therefore in the females' interest to mate with their own males.
Red and blue light
Yet how did these differences evolve? The red species occurs in deeper water than the blue species and therefore experiences different light conditions. Behavioural experiments showed that both species have adapted to this: the red species is more sensitive to red light and the blue species is more sensitive to blue light. For females of the red species, red males are therefore more conspicuous than blue ones, and vice versa. Males of other colours are inconspicuous and unattractive, and therefore produce few offspring. Eventually only the bright red and bright blue fish remain, and two separate species can arise.
Due to the introduction of the Nile perch, deforestation and population growth, water transparency in Lake Victoria is declining. In turbid water, cichlid females are less choosy and males are less brightly coloured. This research therefore underlines the importance of measures to counteract the ongoing eutrophication of the lake.
Evolutionary theory predicts that species can diverge if different females choose different characteristics in males. Yet females often pay attention to traits that reveal something about the quality of a male. As a result, females are likely to share the same preferences. In Lake Victoria cichlid fish, Martine Maan found a solution for this paradox: in different species, different traits reveal male quality.
She examined two closely related species, one with blue males and the other with red males. Females prefer males of the right colour, blue or red, and within those categories they choose the most brightly coloured males. They do so for good reasons: brightly coloured males from both species carry fewer parasites and are thus in better condition. Moreover, both species are adapted to different infection risks, which are associated with a difference in water depth and food choice. It is therefore in the females' interest to mate with their own males.
Red and blue light
Yet how did these differences evolve? The red species occurs in deeper water than the blue species and therefore experiences different light conditions. Behavioural experiments showed that both species have adapted to this: the red species is more sensitive to red light and the blue species is more sensitive to blue light. For females of the red species, red males are therefore more conspicuous than blue ones, and vice versa. Males of other colours are inconspicuous and unattractive, and therefore produce few offspring. Eventually only the bright red and bright blue fish remain, and two separate species can arise.
Due to the introduction of the Nile perch, deforestation and population growth, water transparency in Lake Victoria is declining. In turbid water, cichlid females are less choosy and males are less brightly coloured. This research therefore underlines the importance of measures to counteract the ongoing eutrophication of the lake.
Multiple Genes Permit Closely Related Fish Species To Mix And Match Their Color Vision
ScienceDaily (Oct. 16, 2005) — Vision, like other biological attributes, is shaped by evolution through environmental pressures and demands, and even closely-related species that are in other ways very similar might respond to their particular environments by interpreting the visual world slightly differently, using photoreceptors that are attuned to particular wavelengths of light. By studying a special group of closely-related fish species inhabiting the Great Lakes of Africa, researchers have uncovered clues to understanding how the components of color vision can undergo change over a relatively short period of evolutionary time.
The work is reported by James K. Bowmaker of University College London, Karen L. Carleton of the University of New Hampshire, and their colleagues.
Cichlid fish of the East African Rift Lakes are renowned for their diversity: Owing to migrations of ancestor species out of Lake Tanganyika and into other lakes, such as Lake Malawi, it has been estimated that hundreds of new cichlid species have arisen in these lakes in the last 100,000 years. Thanks to the relatively recent colonization by these fish of different ecological niches, as well as the prominent role of nuptual coloring in the mating preferences of these species, the cichlids offer a unique opportunity to study how color vision can undergo change in rapidly evolving species. For example, because color plays a significant role in mate choice, differences in color vision could greatly influence and even drive cichlid speciation.
In the new work, the researchers performed physiological and molecular genetic analyses of color vision in cichlid fish from Lake Malawi and demonstrated that differences in color vision between closely related species arise from individual species' using different subsets of distinct visual pigments. The scientists showed that although an unexpectedly large group of these visual pigments are available to all the species, each expresses the pigments selectively, and in an individual way, resulting in differences in how the visual world is sensed.
The researchers identified a total of seven "cone" (color-sensing) visual pigments underlying color vision in these cichlids. They have measured the sensitivities of the cones to different wavelengths of light and isolated the seven genes that give rise to the pigment proteins. The seven cone types have maximum sensitivities ranging from the red end of the spectrum right through to the ultraviolet--light outside the range of human sensitivity. The researchers showed that in order to tune its color vision, each cichlid species primarily expresses three of the seven cone pigment genes encoded by their genomes.
It is not clear why such closely related cichlid species have evolved such different visual sensitivities, but the sensitivities most likely relate to such selective forces as foraging specializations and subtle differences in the underwater light environment. Evolutionary comparison of pigment genes suggests that other groups of fish may use a similar strategy for shaping their color vision.
###
The researchers included Juliet W.L. Parry, Aba Carboo, David M. Hunt, and James K. Bowmaker of University College in London, United Kingdom; Karen L. Carleton and Tyrone Spady of the University of New Hampshire, Durham, New Hampshire. This work was supported by the Leverhulme Trust and by the National Science Foundation.
Parry et al.: "Mix and match colour vision: tuning spectral sensitivity by differential opsin gene expression in Lake Malawi cichlids." Publishing in Current Biology, Vol. 15, pages 1734-1739, October 11, 2005. DOI 10.1016/j.cub.2005.08.010 www.current-biology.com
The work is reported by James K. Bowmaker of University College London, Karen L. Carleton of the University of New Hampshire, and their colleagues.
Cichlid fish of the East African Rift Lakes are renowned for their diversity: Owing to migrations of ancestor species out of Lake Tanganyika and into other lakes, such as Lake Malawi, it has been estimated that hundreds of new cichlid species have arisen in these lakes in the last 100,000 years. Thanks to the relatively recent colonization by these fish of different ecological niches, as well as the prominent role of nuptual coloring in the mating preferences of these species, the cichlids offer a unique opportunity to study how color vision can undergo change in rapidly evolving species. For example, because color plays a significant role in mate choice, differences in color vision could greatly influence and even drive cichlid speciation.
In the new work, the researchers performed physiological and molecular genetic analyses of color vision in cichlid fish from Lake Malawi and demonstrated that differences in color vision between closely related species arise from individual species' using different subsets of distinct visual pigments. The scientists showed that although an unexpectedly large group of these visual pigments are available to all the species, each expresses the pigments selectively, and in an individual way, resulting in differences in how the visual world is sensed.
The researchers identified a total of seven "cone" (color-sensing) visual pigments underlying color vision in these cichlids. They have measured the sensitivities of the cones to different wavelengths of light and isolated the seven genes that give rise to the pigment proteins. The seven cone types have maximum sensitivities ranging from the red end of the spectrum right through to the ultraviolet--light outside the range of human sensitivity. The researchers showed that in order to tune its color vision, each cichlid species primarily expresses three of the seven cone pigment genes encoded by their genomes.
It is not clear why such closely related cichlid species have evolved such different visual sensitivities, but the sensitivities most likely relate to such selective forces as foraging specializations and subtle differences in the underwater light environment. Evolutionary comparison of pigment genes suggests that other groups of fish may use a similar strategy for shaping their color vision.
###
The researchers included Juliet W.L. Parry, Aba Carboo, David M. Hunt, and James K. Bowmaker of University College in London, United Kingdom; Karen L. Carleton and Tyrone Spady of the University of New Hampshire, Durham, New Hampshire. This work was supported by the Leverhulme Trust and by the National Science Foundation.
Parry et al.: "Mix and match colour vision: tuning spectral sensitivity by differential opsin gene expression in Lake Malawi cichlids." Publishing in Current Biology, Vol. 15, pages 1734-1739, October 11, 2005. DOI 10.1016/j.cub.2005.08.010 www.current-biology.com
Adaptation To Parasites Drive African Fishes Along Different Evolutionary Paths
Captured from :
http://www.sciencedaily.com/releases/2007/08/070815101856.htm
ScienceDaily (Aug. 16, 2007) — An international team of scientists from Canada (Université Laval), the U.K. (University of Hull, Cardiff University) and Spain (Doòana Biological Station), have discovered that a pair of closely related species of East African cichlid fishes -- a group of fish whose diversity comprising hundreds of species has puzzled evolutionary biologists for decades -- evolved divergent immune gene adaptations which might explain why they do not interbreed, despite living side by side.
The two species ( Pseudotropheus emmiltos and Pseudotropheus fainzilberi ) are found in the north western part of Lake Malawi. Until now, the only known difference between them was the color of their dorsal fin. Many researchers believe that African cichlids recognize conspecifics from these kinds of colour differences, which are thought to result from sexual selection. However, recent mate choice experiments have shown that female P. emmiltos recognize males of their own species from P. fainzilberi males based on olfactory communication rather than color.
Some of the genes known to influence mating behavior through olfaction in other vertebrate species are genes of the major histocompatibility complex (MHC). These genes code for receptor that bound molecules produced by infectious agents and present them to specialized cells of the immune system which then launch an immune attack on the microbes.
They are the most diverse genes found in vertebrate genomes and individuals of some species, including humans, are able to "smell" other individuals' variability at these genes and adjust their mate choice in order to optimize the effectiveness of their offspring's immune system. Analysis of MHC genes between P. emmiltos and P. fainzilberi revealed that the two species were genetically more different at these sites involved in contacting and presenting molecules to immune cells than at other sites of the gene's DNA sequence that do not play functional roles.
These results show that natural selection has driven the evolution of these genes in different direction between the two species. Furthermore, the researchers showed that infecting parasites found on the two species were significantly different, as predicted based on the known immune function of MHC genes. "The mechanisms having produced the hundreds of species of East African cichlid fishes in a relatively short period of time are unclear", says Jonatan Blais, the senior author of the paper. "This is one of the first genetic adaptive differences between closely related East African cichlid species identified. As such, it improves our understanding of the recent evolution of this incredibly diverse group of fish by pointing to a trait that not only diverged for adaptive reasons but may also be involved in mating behavior."
"The precise role that this divergence played in the evolution of reproductive isolation has yet to be studied", comments Louis Bernatchez, co-author of the study." But it offers an exciting new perspective in the study of African cichlids speciation. "
Citation: Blais J, Rico C, van Oosterhout C, Cable J, Turner GF, et al (2007) MHC Adaptive Divergence between Closely Related and Sympatric African Cichlids. PLoS One 2(8): e734. doi:10.1371/journal.pone.0000734
http://www.sciencedaily.com/releases/2007/08/070815101856.htm
ScienceDaily (Aug. 16, 2007) — An international team of scientists from Canada (Université Laval), the U.K. (University of Hull, Cardiff University) and Spain (Doòana Biological Station), have discovered that a pair of closely related species of East African cichlid fishes -- a group of fish whose diversity comprising hundreds of species has puzzled evolutionary biologists for decades -- evolved divergent immune gene adaptations which might explain why they do not interbreed, despite living side by side.
The two species ( Pseudotropheus emmiltos and Pseudotropheus fainzilberi ) are found in the north western part of Lake Malawi. Until now, the only known difference between them was the color of their dorsal fin. Many researchers believe that African cichlids recognize conspecifics from these kinds of colour differences, which are thought to result from sexual selection. However, recent mate choice experiments have shown that female P. emmiltos recognize males of their own species from P. fainzilberi males based on olfactory communication rather than color.
Some of the genes known to influence mating behavior through olfaction in other vertebrate species are genes of the major histocompatibility complex (MHC). These genes code for receptor that bound molecules produced by infectious agents and present them to specialized cells of the immune system which then launch an immune attack on the microbes.
They are the most diverse genes found in vertebrate genomes and individuals of some species, including humans, are able to "smell" other individuals' variability at these genes and adjust their mate choice in order to optimize the effectiveness of their offspring's immune system. Analysis of MHC genes between P. emmiltos and P. fainzilberi revealed that the two species were genetically more different at these sites involved in contacting and presenting molecules to immune cells than at other sites of the gene's DNA sequence that do not play functional roles.
These results show that natural selection has driven the evolution of these genes in different direction between the two species. Furthermore, the researchers showed that infecting parasites found on the two species were significantly different, as predicted based on the known immune function of MHC genes. "The mechanisms having produced the hundreds of species of East African cichlid fishes in a relatively short period of time are unclear", says Jonatan Blais, the senior author of the paper. "This is one of the first genetic adaptive differences between closely related East African cichlid species identified. As such, it improves our understanding of the recent evolution of this incredibly diverse group of fish by pointing to a trait that not only diverged for adaptive reasons but may also be involved in mating behavior."
"The precise role that this divergence played in the evolution of reproductive isolation has yet to be studied", comments Louis Bernatchez, co-author of the study." But it offers an exciting new perspective in the study of African cichlids speciation. "
Citation: Blais J, Rico C, van Oosterhout C, Cable J, Turner GF, et al (2007) MHC Adaptive Divergence between Closely Related and Sympatric African Cichlids. PLoS One 2(8): e734. doi:10.1371/journal.pone.0000734
Friday, February 1, 2008
'Bizarre' new mammal discovered
DISCOVERY OR NAMING UNNAMED SPCIES??
The question above can only be answered by people who
keep on discivering things which have already been there
in millenia.
Hastings
=========
By Rebecca Morelle Science reporter, BBC News
A new species of mammal has been discovered in the mountains of Tanzania, scientists report.
The bizarre-looking creature, dubbed Rhynochocyon udzungwensis, is a type of giant elephant shrew, or sengi.
The cat-sized animal, which is reported in the Journal of Zoology, looks like a cross between a miniature antelope and a small ant eater.
It has a grey face, a long, flexible snout, a bulky, amber body, a jet-black rump and it stands on spindly legs.
"This is one of the most exciting discoveries of my career," said Galen Rathbun, from the California Academy of Sciences, who helped to confirm the animal was new to science along with an international team of colleagues.
They are so bizarre-looking and a lot of their behavioural ecology is so unique and interesting, you kind of get wrapped up with them
Galen Rathbun
Despite its name, the creature, along with the 15 other known species of elephant shrew, is not actually related to shrews.
Dr Rathbun told the BBC News website: "Elephant shrews are only found in Africa. They were originally described as shrews because they superficially resembled shrews in Europe and in America."
In fact, the creature is more closely related to a group of African mammals, which include elephants, sea cows, aardvarks and hyraxes, having shared a common ancestor with them about 100 million years ago.
"This is why they are also known as sengis," explained Dr Rathbun.
The new species was first caught on film in 2005 in Ndundulu Forest in Tanzania's Udzungwa Mountains by a camera trap set by Francesco Rovero, from the Trento Museum of Natural Sciences in Italy.
Dr Rathbun said: "I got these images, and said to myself: 'Boy, these look strange'. But you can't describe something new based just on photographs, so in March 2006, we went back in and collected some specimens."
Flashy creatures
He told the BBC that it quickly became apparent that the creatures were new to science.
He said: "Elephant shrews are almost all distinguished by distinctive colour patterns, and this is especially true of the forest-dwelling giant sengis.
The animal uses its long snout for scooping up insects
"They are all quite flashy - one species has a bright golden rump, another checkers along the rump - so when you have a colour pattern that just isn't similar to what is out there, you know it is fairly obvious that you have got something new.
"And this one, with its grey face and black rump, was pretty different."
As well as its distinctive colouring, the new species was also larger than other species of giant elephant shrew, weighing 700g (25oz) and measuring about 30cm (12in) in length.
It uses its long, flexible nose and tongue to flick up insects, such as termites, and it is most active either at dawn, dusk, or during the day.
Dr Rathbun added: "They are behaviourally fairly simple - they are not like a dog or cat you can interact with - but they are so bizarre-looking and a lot of their behavioural ecology is so unique and interesting, you kind of get wrapped up with them."
The scientists say there is still much to learn about the Rhynochocyon udzungwensis, but they hope further research will help to answer questions about how many of the animals exist, their range and how closely the animals live together.
Tanzania's Udzungwa Mountains are rich in biodiversity, in addition to this new species, a number of other new species have been found there, including the Udzungwa partridge, the Phillips' Congo shrew, and a new genus of monkey known as Kipunji as well as several reptiles and amphibians.
Dr Rathbun said it was vital the area and its inhabitants in this "biodiversity hotspot" were protected.
The question above can only be answered by people who
keep on discivering things which have already been there
in millenia.
Hastings
=========
By Rebecca Morelle Science reporter, BBC News
A new species of mammal has been discovered in the mountains of Tanzania, scientists report.
The bizarre-looking creature, dubbed Rhynochocyon udzungwensis, is a type of giant elephant shrew, or sengi.
The cat-sized animal, which is reported in the Journal of Zoology, looks like a cross between a miniature antelope and a small ant eater.
It has a grey face, a long, flexible snout, a bulky, amber body, a jet-black rump and it stands on spindly legs.
"This is one of the most exciting discoveries of my career," said Galen Rathbun, from the California Academy of Sciences, who helped to confirm the animal was new to science along with an international team of colleagues.
They are so bizarre-looking and a lot of their behavioural ecology is so unique and interesting, you kind of get wrapped up with them
Galen Rathbun
Despite its name, the creature, along with the 15 other known species of elephant shrew, is not actually related to shrews.
Dr Rathbun told the BBC News website: "Elephant shrews are only found in Africa. They were originally described as shrews because they superficially resembled shrews in Europe and in America."
In fact, the creature is more closely related to a group of African mammals, which include elephants, sea cows, aardvarks and hyraxes, having shared a common ancestor with them about 100 million years ago.
"This is why they are also known as sengis," explained Dr Rathbun.
The new species was first caught on film in 2005 in Ndundulu Forest in Tanzania's Udzungwa Mountains by a camera trap set by Francesco Rovero, from the Trento Museum of Natural Sciences in Italy.
Dr Rathbun said: "I got these images, and said to myself: 'Boy, these look strange'. But you can't describe something new based just on photographs, so in March 2006, we went back in and collected some specimens."
Flashy creatures
He told the BBC that it quickly became apparent that the creatures were new to science.
He said: "Elephant shrews are almost all distinguished by distinctive colour patterns, and this is especially true of the forest-dwelling giant sengis.
The animal uses its long snout for scooping up insects
"They are all quite flashy - one species has a bright golden rump, another checkers along the rump - so when you have a colour pattern that just isn't similar to what is out there, you know it is fairly obvious that you have got something new.
"And this one, with its grey face and black rump, was pretty different."
As well as its distinctive colouring, the new species was also larger than other species of giant elephant shrew, weighing 700g (25oz) and measuring about 30cm (12in) in length.
It uses its long, flexible nose and tongue to flick up insects, such as termites, and it is most active either at dawn, dusk, or during the day.
Dr Rathbun added: "They are behaviourally fairly simple - they are not like a dog or cat you can interact with - but they are so bizarre-looking and a lot of their behavioural ecology is so unique and interesting, you kind of get wrapped up with them."
The scientists say there is still much to learn about the Rhynochocyon udzungwensis, but they hope further research will help to answer questions about how many of the animals exist, their range and how closely the animals live together.
Tanzania's Udzungwa Mountains are rich in biodiversity, in addition to this new species, a number of other new species have been found there, including the Udzungwa partridge, the Phillips' Congo shrew, and a new genus of monkey known as Kipunji as well as several reptiles and amphibians.
Dr Rathbun said it was vital the area and its inhabitants in this "biodiversity hotspot" were protected.
Tuesday, January 22, 2008
HUMAN EVOLUTION IS SPEEDING UP
Hi
Hard facts to take them head on.
hastings
========
Human evolution is speeding up
Taken from BBC NEWS
By Anna-Marie Lever Science and nature reporter, BBC News
Humans have moved into the evolutionary fast lane and are becoming increasingly different, a genetic study suggests.
In the past 5,000 years, genetic change has occurred at a rate roughly 100 times higher than any other period, say scientists in the US.
This is in contrast with the widely-held belief that recent human evolution has halted.
The research has been published in the Proceedings of the National Academy of Sciences (PNAS).
Professor Henry Harpending, an author of the study from the University of Utah, Salt Lake City, US, said: "The dogma has been these [differences] are cultural fluctuations, but almost any temperament trait you look at is under strong genetic influences.
"Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin," he added. "We are getting less alike, not merging into a single, mixed humanity."
This is happening, he said, because "there has not been much flow" between different regions since modern humans left Africa to colonise the rest of the world. And there is no evidence that it is slowing down, he added.
"The technology can't detect anything beyond about 2,000 years ago, but we see no sign of [human evolution] slowing down. So I would suspect it is continuing," he told BBC News.
New gene selection
Researchers found evidence of recent selection in 7% of all human genes, including lighter skin and blue eyes in northern Europe and partial resistance to diseases, such as malaria, among some African populations.
At the moment we are in an evolutionary interval. We are in between two storms
Professor Steve Jones, geneticist
"Five thousand years is such a small sliver of time," said co-author Professor John Hawks of the University of Wisconsin, Madison. "It's 100 or 200 generations ago. That's how long since some of these genes originated, and today they are in 30% or 40% of people because they've had such an advantage."
The researchers propose that there are two factors causing human evolution to speed up.
"One of them is there are a lot more people - the more people you have the more opportunities there are for an advantageous mutation to show up," said Professor Harpending.
A large population has more genetic variation and allows for more positive selection than a small one.
"The second is environmental change - our diets have changed, we are in radically new environments," he added. "With a large population size comes lots of new diseases."
Happening now?
However, geneticist Professor Steve Jones of University College London said suggesting a large population size could increase the speed of evolution was "a contentious issue".
Seven percent of human genes are undergoing rapid evolution
"Once a population gets above a very small size it is not very clear if its ability to respond to natural selection depends on size," he told BBC News.
"The general picture that evolution has speeded up in the last 10,000 years as we change from, to put it bluntly, being animals to being humans is clearly true," he explained. "To suggest it is happening at this instant, I would suggest, is probably wrong."
He said natural selection needed difference - either in the ability to stay alive or in the number of offspring born.
"The fundamental observation is that this difference has gone," said Professor Jones.
"At the moment we are in an evolutionary interval. We are in between two storms. One storm has more or less blown itself out, the storm of farming.
"The question is whether we are going to stay in the calms or whether another great storm will start. And if there is one, I would say it is most certainly to do with epidemic disease."
How they did it
The study looked specifically at genetic variations called "single nucleotide polymorphisms," or SNPs. These are single-point mutations, or changes, in the genetic sequence of DNA on chromosomes.
If the mutation is advantageous then it will spread rapidly in the population, along with DNA on either side of the mutation.
The authors argued that if the same chromosome from numerous people had a segment with an identical pattern of SNPs this would indicate that the segment of the chromosome had not been broken up (recombined) recently.
Hard facts to take them head on.
hastings
========
Human evolution is speeding up
Taken from BBC NEWS
By Anna-Marie Lever Science and nature reporter, BBC News
Humans have moved into the evolutionary fast lane and are becoming increasingly different, a genetic study suggests.
In the past 5,000 years, genetic change has occurred at a rate roughly 100 times higher than any other period, say scientists in the US.
This is in contrast with the widely-held belief that recent human evolution has halted.
The research has been published in the Proceedings of the National Academy of Sciences (PNAS).
Professor Henry Harpending, an author of the study from the University of Utah, Salt Lake City, US, said: "The dogma has been these [differences] are cultural fluctuations, but almost any temperament trait you look at is under strong genetic influences.
"Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin," he added. "We are getting less alike, not merging into a single, mixed humanity."
This is happening, he said, because "there has not been much flow" between different regions since modern humans left Africa to colonise the rest of the world. And there is no evidence that it is slowing down, he added.
"The technology can't detect anything beyond about 2,000 years ago, but we see no sign of [human evolution] slowing down. So I would suspect it is continuing," he told BBC News.
New gene selection
Researchers found evidence of recent selection in 7% of all human genes, including lighter skin and blue eyes in northern Europe and partial resistance to diseases, such as malaria, among some African populations.
At the moment we are in an evolutionary interval. We are in between two storms
Professor Steve Jones, geneticist
"Five thousand years is such a small sliver of time," said co-author Professor John Hawks of the University of Wisconsin, Madison. "It's 100 or 200 generations ago. That's how long since some of these genes originated, and today they are in 30% or 40% of people because they've had such an advantage."
The researchers propose that there are two factors causing human evolution to speed up.
"One of them is there are a lot more people - the more people you have the more opportunities there are for an advantageous mutation to show up," said Professor Harpending.
A large population has more genetic variation and allows for more positive selection than a small one.
"The second is environmental change - our diets have changed, we are in radically new environments," he added. "With a large population size comes lots of new diseases."
Happening now?
However, geneticist Professor Steve Jones of University College London said suggesting a large population size could increase the speed of evolution was "a contentious issue".
Seven percent of human genes are undergoing rapid evolution
"Once a population gets above a very small size it is not very clear if its ability to respond to natural selection depends on size," he told BBC News.
"The general picture that evolution has speeded up in the last 10,000 years as we change from, to put it bluntly, being animals to being humans is clearly true," he explained. "To suggest it is happening at this instant, I would suggest, is probably wrong."
He said natural selection needed difference - either in the ability to stay alive or in the number of offspring born.
"The fundamental observation is that this difference has gone," said Professor Jones.
"At the moment we are in an evolutionary interval. We are in between two storms. One storm has more or less blown itself out, the storm of farming.
"The question is whether we are going to stay in the calms or whether another great storm will start. And if there is one, I would say it is most certainly to do with epidemic disease."
How they did it
The study looked specifically at genetic variations called "single nucleotide polymorphisms," or SNPs. These are single-point mutations, or changes, in the genetic sequence of DNA on chromosomes.
If the mutation is advantageous then it will spread rapidly in the population, along with DNA on either side of the mutation.
The authors argued that if the same chromosome from numerous people had a segment with an identical pattern of SNPs this would indicate that the segment of the chromosome had not been broken up (recombined) recently.
Saturday, January 19, 2008
TATA NANO TECHNOLOGY
Thanks to Dr Gwynne Dyer
It takes a man to put down the sentiments in your article
and you are proving to be one of the best brains on our
planet earth.
You set in a good novel thesis alltogether of what it takes
to reduce the carbon emmissions.
Hastings
=========
Nano Hypocrisy
By Gwynne Dyer
http://www.gwynnedy er.net/articles/ Gwynne%20Dyer% 20article_ %20%20Tehran% 20Times.txt
The jokes about the Nano, Tata Motors' new affordable car for theIndian middle class, were harmless, although very old. They told the samejokes about the Fiat 500 and the Citroen 2CV in the 1950s, when mass carownership first came to Europe. "How do you double the value of a Nano?""Fill the tank." "How many engineers does it take to make a Nano?" "Two.One to fold and one to apply the glue." But the hypocrisy wasn't funny atall.
The typical story in the Western media began by marvelling thatTata has managed to build a car that will sell for only 100,000 rupees (US$2,500). Everybody agrees that it's "cute", and it will take five peopleprovided they don't all inhale at the same time. It has no radio, no airconditioning, and only one big windshield wiper, but such economies meanthat it really is within reach of tens of millions of Indians who couldonly afford a scooter up to now. And that is where the hypocrisy kicked in.
What will become of us when all those Indians start driving aroundin cars? There's over a billion of them, and the world just can't take anymore emissions. It's not the "People's Car," as Tata bills it, but ratherthe "People's Polluter," moaned Canada's National Post. "A few dozenmillion new cars pumping out pollution in a state of semi-permanentgridlock is hardly what the Kyoto Protocol had in mind."
But hang on a minute. Aren't there more than a dozen million carsin Canada already, even though it only has one-thirtieth of India'spopulation? Aren't they on average twice the size of the Nano (or, in thecase of the larger SUV's, five times the size)? Does the phrase "doublestandard" come to mind?
"India's vehicles spewed 219 million tonnes of carbon dioxide intothe atmosphere in 2005," fretted The Guardian in London. "Experts say thatfigure will jump almost sevenfold to 1,470 million tonnes by 2035 if cartravel remains unchecked." And the Washington Post wrote: "If millions ofIndians and Chinese get to have their own cars, the planet is doomed.Suddenly, the cute little Nano starts to look a lot less winning." Butpractically every family in the United States and Britain already has itsown car (or two).
Don't they realise how ugly it sounds? Don't they understand thateverybody on the planet has an equal right to own a car, if they can affordit? If the total number of people who can afford cars exceeds the numberof cars that the planet can tolerate, then we will just have to work out arationing system that everybody finds fair, or live with the consequencesof exceeding the limits.
"Contraction and convergence" is the phrase they need to learn. Itwas coined almost twenty years ago by South African-born activist AubreyMeyer, founder of the Global Commons Institute, and it is still the onlyplausible way that we might get global agreement on curbing greenhouse gasemissions worldwide.
The notion is simply that we must agree on a figure for totalglobal emissions that cannot be exceeded, rather as we set fishing quotasin order to preserve fish stocks. Then we divide that amount by six and ahalf billion (the total population of the planet), and that gives us theper capita emission limit for everyone on Earth.
Of course, some people (in the developed countries, mostly) arecurrently emitting ten or twenty times as much as other people (mainly inthe developing countries), but eventually that will have to stop. The bigemitters will gradually have to "contract" their per capita emissions,while the poor countries may continue to grow theirs, until at an agreeddate some decades in the future the two groups "converge" at the same levelof per capita emissions. And that level, by prior agreement, will be lowenough that global emissions remain below the danger point.
If you don't like that idea, then you can go with the alternative:a free-for-all world in which everybody moves towards the level of percapita emissions that now prevails in the developed countries. Nonegotiations or treaties required: it will happen of its own accord. Sowill runaway climate change, with average global temperatures as much as 6degrees C (10 degrees F) higher by the end of the century. That means afuture of famine, war and mass death.
Clucking disapprovingly about mass car ownership in India or Chinamisses the point entirely. At the moment there are only eleven privatecars for every thousand Indians. There are 477 cars for every thousandAmericans. By mid-century, there will have to be the same number of carsper thousand people for both Indians and Americans -- and that number willhave to be a lot lower than 477, unless somebody comes up with cars thatemit no greenhouse gases at all. Otherwise, everybody loses.
____________ _________ _________ ________
To shorten to 725 words, omit paragraphs 3 and 4. ("What will...mind? ") Gwynne Dyer is a London-based independent journalist whose articlesare published in 45 countries.
It takes a man to put down the sentiments in your article
and you are proving to be one of the best brains on our
planet earth.
You set in a good novel thesis alltogether of what it takes
to reduce the carbon emmissions.
Hastings
=========
Nano Hypocrisy
By Gwynne Dyer
http://www.gwynnedy er.net/articles/ Gwynne%20Dyer% 20article_ %20%20Tehran% 20Times.txt
The jokes about the Nano, Tata Motors' new affordable car for theIndian middle class, were harmless, although very old. They told the samejokes about the Fiat 500 and the Citroen 2CV in the 1950s, when mass carownership first came to Europe. "How do you double the value of a Nano?""Fill the tank." "How many engineers does it take to make a Nano?" "Two.One to fold and one to apply the glue." But the hypocrisy wasn't funny atall.
The typical story in the Western media began by marvelling thatTata has managed to build a car that will sell for only 100,000 rupees (US$2,500). Everybody agrees that it's "cute", and it will take five peopleprovided they don't all inhale at the same time. It has no radio, no airconditioning, and only one big windshield wiper, but such economies meanthat it really is within reach of tens of millions of Indians who couldonly afford a scooter up to now. And that is where the hypocrisy kicked in.
What will become of us when all those Indians start driving aroundin cars? There's over a billion of them, and the world just can't take anymore emissions. It's not the "People's Car," as Tata bills it, but ratherthe "People's Polluter," moaned Canada's National Post. "A few dozenmillion new cars pumping out pollution in a state of semi-permanentgridlock is hardly what the Kyoto Protocol had in mind."
But hang on a minute. Aren't there more than a dozen million carsin Canada already, even though it only has one-thirtieth of India'spopulation? Aren't they on average twice the size of the Nano (or, in thecase of the larger SUV's, five times the size)? Does the phrase "doublestandard" come to mind?
"India's vehicles spewed 219 million tonnes of carbon dioxide intothe atmosphere in 2005," fretted The Guardian in London. "Experts say thatfigure will jump almost sevenfold to 1,470 million tonnes by 2035 if cartravel remains unchecked." And the Washington Post wrote: "If millions ofIndians and Chinese get to have their own cars, the planet is doomed.Suddenly, the cute little Nano starts to look a lot less winning." Butpractically every family in the United States and Britain already has itsown car (or two).
Don't they realise how ugly it sounds? Don't they understand thateverybody on the planet has an equal right to own a car, if they can affordit? If the total number of people who can afford cars exceeds the numberof cars that the planet can tolerate, then we will just have to work out arationing system that everybody finds fair, or live with the consequencesof exceeding the limits.
"Contraction and convergence" is the phrase they need to learn. Itwas coined almost twenty years ago by South African-born activist AubreyMeyer, founder of the Global Commons Institute, and it is still the onlyplausible way that we might get global agreement on curbing greenhouse gasemissions worldwide.
The notion is simply that we must agree on a figure for totalglobal emissions that cannot be exceeded, rather as we set fishing quotasin order to preserve fish stocks. Then we divide that amount by six and ahalf billion (the total population of the planet), and that gives us theper capita emission limit for everyone on Earth.
Of course, some people (in the developed countries, mostly) arecurrently emitting ten or twenty times as much as other people (mainly inthe developing countries), but eventually that will have to stop. The bigemitters will gradually have to "contract" their per capita emissions,while the poor countries may continue to grow theirs, until at an agreeddate some decades in the future the two groups "converge" at the same levelof per capita emissions. And that level, by prior agreement, will be lowenough that global emissions remain below the danger point.
If you don't like that idea, then you can go with the alternative:a free-for-all world in which everybody moves towards the level of percapita emissions that now prevails in the developed countries. Nonegotiations or treaties required: it will happen of its own accord. Sowill runaway climate change, with average global temperatures as much as 6degrees C (10 degrees F) higher by the end of the century. That means afuture of famine, war and mass death.
Clucking disapprovingly about mass car ownership in India or Chinamisses the point entirely. At the moment there are only eleven privatecars for every thousand Indians. There are 477 cars for every thousandAmericans. By mid-century, there will have to be the same number of carsper thousand people for both Indians and Americans -- and that number willhave to be a lot lower than 477, unless somebody comes up with cars thatemit no greenhouse gases at all. Otherwise, everybody loses.
____________ _________ _________ ________
To shorten to 725 words, omit paragraphs 3 and 4. ("What will...mind? ") Gwynne Dyer is a London-based independent journalist whose articlesare published in 45 countries.
Monday, January 7, 2008
2008 greetings to all
Hi
2008 is here, I will be bring more scientific news in biotechnology,
field this year.
wishing you all the best of 2008.
hastings
2008 is here, I will be bring more scientific news in biotechnology,
field this year.
wishing you all the best of 2008.
hastings
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