Environment's Effects On Evolution of Survival Traits

ScienceDaily (Feb. 11, 2012) — Advances in studying genes mean that scientists in evolutionary developmental biology or "evo-devo" can now explain more clearly than ever before how bats got wings, the turtle got its shell and blind cave fish lost their eyes, says University of Massachusetts Amherst evolutionary biologist Craig Albertson.

He recently won a five-year, $625,000 Faculty Early Career Development grant from the National Science Foundation (NSF) to study the evo-devo of jaws in cichlid fish, tropical freshwater relatives of the tilapia. These highly adaptable cousins of sunfish, usually medium-sized and looking a bit like perch, have a phenomenal ability to undergo evolutionary change. They've developed 1,000 new species in Lake Malawi, Africa, over the past million years, a far faster pace than usual for other vertebrates in a similar period.

The NSF grant is the foundation's most prestigious award in support of junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education and the integration of both.

Read on:  http://www.sciencedaily.com/releases/2012/02/120211095049.htm

Zebra stripes evolved to keep biting flies at bay

By Victoria GillScience reporter, BBC Nature

Why zebras evolved their characteristic black-and-white stripes has been the subject of decades of debate among scientists.

Now researchers from Hungary and Sweden claim to have solved the mystery.

The stripes, they say, came about to keep away blood-sucking flies.

They report in the Journal of Experimental Biology that this pattern of narrow stripes makes zebras "unattractive" to the flies.

They key to this effect is in how the striped patterns reflect light.

"We started off studying horses with black, brown or white coats," explained Susanne Akesson from Lund University, a member of the international research team that carried out the study.

"We found that in the black and brown horses, we get horizontally polarised light." This effect made the dark-coloured horses very attractive to flies.

It means that the light that bounces off the horse's dark coat - and travels in waves to the eyes of a hungry fly - moves along a horizontal plane, like a snake slithering along with its body flat to the floor.

Dr Akesson and her colleagues found that horseflies, or tabanids, were very attracted by these "flat" waves of light.

"From a white coat, you get unpolarised light [reflected]," she explained. Unpolarised light waves travel along any and every plane, and are much less attractive to flies. As a result, white-coated horses are much less troubled by horseflies than their dark-coloured relatives.

http://news.bbcimg.co.uk/media/images/58391000/jpg/_58391196_dscf6956_gabor-horvath.jpg

Read on: http://www.bbc.co.uk/nature/16944753

Castaway Lizards Provide Insight Into Elusive Evolutionary Process, Founder Effects (via Herp Digest)

ScienceDaily (Feb. 2, 2012) 

A University of Rhode Island biologist who released lizards on tiny uninhabited islands in the Bahamas has shed light on the interaction between evolutionary 

Jason Kolbe, a URI assistant professor of biological sciences, and colleagues from Duke University, Harvard University and the University of California at Davis, found that the lizards' genetic and morphological traits were determined by both natural selection and a phenomenon called founder effects, which occur when species colonize new territory.

Their research was published recently in the journal Science.

"We rarely observe founder effects as they happen in nature, but we know that it happens because islands are colonized by new species over time," said Kolbe. "What we didn't know was how these evolutionary mechanisms interact with each other. What we learned is that the differences caused by the founder effects persist even as populations adapt to their new environments."

The founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It often results in the new population becoming genetically or morphologically different from the original population.

The scientists randomly collected brown anole lizards from a large island near Great Abaco and released one pair on each of seven nearby islands whose lizard populations had been cleared by a recent hurricane. The source island is forested while the other islands have short, scrub vegetation. 

Previous research found that anoles living in forests had longer hind limbs than those found in scrub habitat. Lizards with longer limbs can run faster on the broad perches available in forests, while short-limbed lizards are more adept at moving on the narrower perches found in lower vegetation.
The scientists revisited each of the islands over the next four years to measure the lizards' limb length and collect tissue samples for genetic analysis. All of the new populations survived and increased an average of 13-fold in the first two years before leveling off.

"We noticed a founder effect one year after starting the experiment, which resulted in differences among the lizards on the seven islands," Kolbe said. "Some of the islands had lizards with longer limbs and some had lizards with shorter limbs, but that was random with respect to the vegetation on the new islands."

Because the structure of the vegetation on the islands differed from that of the source island, the scientists predicted that natural selection would lead the lizards to develop shorter limbs.
"Over the next four years, the lizards on all the islands experienced a decrease in leg length that is attributable to natural selection," Kolbe explained. "But those that started out with the longest hind limbs still had the longest hind limbs. The fact that the populations maintained their order from longest to shortest limbs throughout the experiment means that both founder effects and natural selection contributed to their current differences."

According to Kolbe, founding effects are rarely observed in nature, with most previous studies being conducted in the laboratory. "Ours is the first to study this process experimentally in a natural setting, and we were able to account for multiple evolutionary mechanisms through time," he said. "We manipulated the founding of these islands, but everything else about it was natural."
The next step in the research will be to determine how long the founder effects persist before other factors erase its signature.

The study was funded by the National Science Foundation and the National Geographic Society.

How Dinosaurs Grew So Huge

How did some dinosaurs reach such soaring heights -- up to 100 feet high in some cases? Efficient lungs and respiration, along with egg laying, might have given dinos a growth edge when compared to other animals, suggests new research.

The study also negates a popular theory that animals tended to become bigger over the course of their evolution.

While some dinosaurs grew ever larger over subsequent generations, not all did.

"We look at the early history of archosaurs, including some early dinosaurs," said Roger Benson who co-authored the study published in the Proceedings of the Royal Society B. "We can see that some lineages obtained gigantic body sizes, but others remained small and a few showed evolutionary size reductions."

Benson, a vertebrate paleontologist at the University of Cambridge, explained that "pterosaurs, the flying reptiles, are a good example of a lineage that remained small during our study interval. There were also many small herbivores, like the dinosaurHeterodontosaurus, and small predators like the dinosaur Coelophysis."

Benson and colleagues Roland Sookias and Richard Butler analyzed more than 400 species spanning the Late Permian to Middle Jurassic periods. The animals' pattern of growth during 100 million years supports a theory called "passive diffusion." This just means that various evolutionary lineages did a bunch of different things, from growing larger to growing smaller.

The findings counter a theory known as "Cope's rule," which claims that some groups, such as dinosaurs, tended to always evolve bigger bodies over time.

There is no question, however, that many dinosaurs were mega huge, at least when compared to today's land animals.

Read more:  http://www.livescience.com/18314-dinosaurs-grew-huge.html

Evolution Is Written All Over Your Face

ScienceDaily (Jan. 11, 2012) — Why are the faces of primates so dramatically different from one another?

UCLA biologists working as "evolutionary detectives" studied the faces of 129 adult male primates from Central and South America, and they offer some answers in research published Jan. 11, in the early online edition of the journal Proceedings of the Royal Society B. The faces they studied evolved over at least 24 million years, they report.

"If you look at New World primates, you're immediately struck by the rich diversity of faces," said Michael Alfaro, a UCLA associate professor of ecology and evolutionary biology and the senior author of the study. "You see bright red faces, moustaches, hair tufts and much more. There are unanswered questions about how faces evolve and what factors explain the evolution of facial features. We're very visually oriented, and we get a lot of information from the face."

Some of theprimate species studied are solitary, while others live in groups that can include dozens or even hundreds of others.

Continued:  http://www.sciencedaily.com/releases/2012/01/120111223744.htm

Mighty arms helped extinct cats keep a mouthful of fanged teeth

Sabertooth cats and other super-toothy predators apparently possessed mighty arms that they used to help them kill.  The beefy arms would have served to pin down prey and protect the ferocious-looking teeth of the feline predators, which were actually fragile enough to fracture, scientists find.  The finding also may hold for other knife-fanged prehistoric carnivores; long before sabertooth cats evolved, a number of now-extinct toothy hunters once roamed the Earth. These included the nimravids, or false sabertooth cats, which lived from 7 million to 42 million years ago alongside a sister group to cats known as barbourofelids, which lived from 5 million to 20 million years ago.  "If you saw one of these animals you'd probably think it was a cat, but true cats didn't evolve until millions of years later," said researcher Julie Meachen-Samuels, a paleontologist at the National Evolutionary Synthesis Center in Durham, N.C.

Read more at: http://www.livescience.com/17723-sabertooth-cats-powerful-arms.html

New Theory Emerges for Where Some Fish Became Four-Limbed Creatures

ScienceDaily (Dec. 27, 2011) — A small fish crawling on stumpy limbs from a shrinking desert pond is an icon of can-do spirit, emblematic of a leading theory for the evolutionary transition between fish and amphibians. This theorized image of such a drastic adaptation to changing environmental conditions, however, may, itself, be evolving into a new picture.

University of Oregon scientist Gregory J. Retallack, professor of geological sciences, says that his discoveries at numerous sites in Maryland, New York and Pennsylvania suggests that "such a plucky hypothetical ancestor of ours probably could not have survived the overwhelming odds of perishing in a trek to another shrinking pond."


This scenario comes from the late Devonian, about 390 million years ago to roughly 360 million years ago. Paleontologist Alfred Romer, who died in 1973 after serving on the faculties at the University of Chicago and Harvard University, saw this time as a period of struggle and escape -- and important in fish-tetrapod transition -- to ensure survival.

Reporting in the May 2011 issue of the Journal of Geology, Retallack, who also is co-director of paleontological collections at the UO's Museum of Natural and Cultural History, argues for a very different explanation. He examined numerous buried soils in rocks yielding footprints and bones of early transitional fossils between fish and amphibians of Devonian and Carboniferous geological age. What he found raises a major challenge to Romer's theory.




Read more here:  http://www.sciencedaily.com/releases/2011/12/111227142628.htm

Rapid evolution in domestic animals

Genetic Study of Black Chickens Shed Light On Mechanisms Causing Rapid Evolution in Domestic Animals


ScienceDaily (Dec. 22, 2011) — The genetic changes underlying the evolution of new species are still poorly understood. Genetic studies in domestic animals can shed light on this process due to the rapid evolution they have undergone over the last 10,000 years. A new study describes how a complex genomic rearrangement causes a fascinating phenotype in chickens.


In the study published in PLoS Genetics researchers at Uppsala University, Swedish University of Agricultural Sciences, North Carolina State University and National Chung-Hsing University have investigated the genetic basis of fibromelanosis, a breed characteristic of the Chinese Silkie chicken (image on left). This trait involves a massive expansion of pigment cells that not only makes the skin and comb black but also causes black internal organs. Chickens similar in appearance to the Silkie were described by Marco Polo when he visited China in the 13th century and Silkie chickens have a long history in Chinese cuisine and traditional Chinese medicine.


"We have shown that the genetic change causing fibromelanosis is a complex rearrangement that leads to increased expression of Endothelin 3, a gene which is known for promoting the growth of pigment cells," explains Ben Dorshorst the post-doctoral researcher responsible for the work.

The research group led by Leif Andersson has by now characterized a number of traits in domestic animals, and a clear trend is emerging, namely that genomic rearrangements have contributed significantly to the rapid evolution of domestic animals. Other examples include Greying with age in horses and mutations affecting the size and shape of the comb in chickens.

"We have good reason to believe that such rearrangements have also played a significant role in the evolution of other species, including ourselves," concludes Leif Andersson.

The researchers also studied other chicken breeds where fibromelanosis occurs, including the Bohuslän-Dals svarthöna breed (image on right) from Sweden, and they found that all fibromelanotic breeds carried the exact same very unusual mutation. This finding is consistent with anecdotal evidence suggesting that this Swedish breed of chicken inherited their black skin and internal connective tissue color from Asian chickens that were first brought to Norway by a sailor on the East Asian trade routes centuries ago. This is a nice example of how humans have distributed a single novel mutation with an interesting effect when they developed breeds of domestic animals around the world. -- It is obvious that humans have had a strong affection for biological diversity in their domestic animals, says Leif Andersson.

http://www.sciencedaily.com/releases/2011/12/111222195009.htm

They Call It 'Guppy Love': Biologists Solve an Evolution Mystery

ScienceDaily (Nov. 23, 2011) — Guppies in the wild have evolved over at least half-a-million years -- long enough for the males' coloration to have changed dramatically. Yet a characteristic orange patch on male guppies has remained remarkably stable, though it could have become redder or more yellow. Why has it stayed the same hue of orange over such a long period of time?

Because that's the color female guppies prefer.

"Sometimes populations have to evolve just to stay the same," said Greg Grether, a UCLA professor of ecology and evolutionary biology and co-author of a study published Nov. 23 in the online edition of the journal Proceedings of the Royal Society B: Biological Sciences, a major journal for research in evolutionary biology.

"In this case, the males have evolved back over and over again to the color that females prefer," said Grether, who noted that there are many examples in which there is less variation among populations of a species than life scientists would expect.

The new study, funded by the National Science Foundation, "provides a neat solution to a mystery that has puzzled me for years," he said.

The orange patches on male guppies are made up of two pigments: carotenoids (which they ingest in their diets and are yellow) and drosopterins (which are red and which their bodies produce).

Carotenoids are the same pigments that provide color to vegetables and fruits. Plants produce carotenoids, but animals generally cannot; guppies obtain most of their carotenoids from algae.

UCLA's Kerry Deere, the lead author of the study, conducted experiments in which she presented female guppies (Poecilia reticulata) with a choice of males with low, medium and high levels of drosopterin to see which males they preferred. In her experiments, the females were given a wider range of pigment choices than they would find in the wild. Deere, who was a graduate student of ecology and evolutionary biology in Grether's laboratory at the time and is currently a UCLA postdoctoral scholar in human genetics, conducted more than 100 mate-choice trials.

The females strongly preferred the intermediate males, those whose patches, or spots, were the right hue of orange -- not too red and not too yellow.

"The females preferred the males with an intermediate drosopterin level by a highly significant margin," Deere said.

"Males that are closer to this preferred hue probably have more offspring," Grether said.

If guppies were dependent only on carotenoids for their orange coloration, one would expect to find large changes in the color of their orange patches because the availability of algae varies by location. Guppies are native to Trinidad and Venezuela; the ones in this study were from Trinidad.

(Unlike the colorful guppies sold in pet stores, female guppies in the wild do not have bright coloration like the orange patches. Males are not as ornate, or as large, as the pet-store variety either.)

"A pattern I discovered 10 years ago, which was mysterious at first, is that in locations where more
carotenoids are available in their diet, guppies produce more of the drosopterins," Grether said. "There is a very strong pattern of the ratio of these two kinds of pigments staying about the same.

Read more here ...

Whiskers Marked Milestone in Evolution of Mammals from Reptiles (Via Herp Digest)

Whiskers Marked Milestone in Evolution of Mammals from Reptiles

The story is reprinted from materials provided by University of Sheffield. (Nov. 10, 2011) - Research from the University of Sheffield comparing rats and mice with their distance relatives the marsupial, suggests that moveable whiskers were an important milestone in the evolution of mammals from reptiles.

Using high-speed digital video recording and automatic tracking, the research team, which was led by Professor Tony Prescott from the University´s Department of Psychology, have shed light on how rodents such as mice and rats move their whiskers back-and-forth at high speed and in varying ways to actively sense the environment around them in a behaviour known as whisking. Whisking allows mice or rats to accurately determine the position, shape and texture of objects, make rapid and accurate decisions about objects, and then use the information to build environmental maps.

When running in a straight line, rats and mice move their whiskers back-and-forth the same amount on both sides. However when turning, they bias their whisker movements in the direction of the turn, and when the whiskers on one side of the head contact an object, those on the opposite side sweep round to gather more information. These active sensing strategies boost the information gained by the whiskers helping the animals to better understand their world through touch.

In their latest research, the team have shown that whisking like that of rodents, using these active sensing strategies, is also seen in a small South American marsupial -- the grey short-tailed opossum. This animal has many similarities to an early mammal that would have lived more than 125 million years ago; that is, around the same time that the evolutionary lines leading to modern rodents and marsupials diverged.

This evidence suggests that some of the first mammals may also have whisked like a modern mouse or rat, and that the appearance of moveable whiskers was pivotal in the evolution of mammals from reptiles. The research is published in Philosophical Transactions of the Royal Society B on 12 November 2011 and will also be presented on the same day at the Society for Neuroscience conference.
The earliest mammals were nocturnal, and tree-living. In order to successfully move around and thrive in this challenging environment these animals needed to effectively integrate information from multiple senses -- sight, sound, smell, and touch. Facial whiskers provided mammals with a new tactile sense not available to reptiles that could help them to get around in the dark.

In addition to continuing to investigate the similarities and differences between rodents and marsupials, the team is also using these insights from biological whisker sensing to develop animal-like robots that can use artificial whiskers to navigate without vision. These robots could have applications in search-and-rescue, particularly in environments, such as disaster sites, where vision is compromised by smoke or dust.

Professor Tony Prescott said: "This latest research suggests that alongside becoming warm-blooded, giving birth to live young, and having an enlarged brain, the emergence of a new tactile sense based on moveable facial whiskers was an important step along the evolutionary path to modern mammals. Although humans no longer have moveable whiskers they were a critical feature of our early mammalian ancestors."

Variation in male, female turtle shells provides advantage when facing predators (Via Herp Digest)

Variation in male, female turtle shells provides advantage when facing predators
Released: 11/15/2011 2:00 PM EST
Source: Allen Press Publishing Services
News Release
FOR IMMEDIATE RELEASE

Newswise - Herpetologica - One way to tell a male turtle from a female turtle is a difference in the shape of their shells. While this pattern of sexual dimorphism is common among turtle species, it could have other effects on turtle biology. The differing shell designs may exhibit different strengths in standing up to the attack of a predator, and therefore the survival rate of one sex over the other.

The current issue of the journal Herpetologica reports on the mechanical implications of shell shape differences between two species of male and female turtles. The Painted Turtle (Chrysemys picta) is an aquatic species, and the Wood Turtle (Glyptemys insculpta) is a terrestrial species.

Females turtles tend to have larger, domed shells, which may indicate the ability to hold large clutches of eggs. Males, on the other hand, typically have flatter shells and larger openings for their limbs, allowing them greater movement. This improves their success in courtship and mating.

To test the strength of these varying shells, researchers created digital models of the shells for finite element analysis. This computer model uses simple geometric shapes to create a complex structure-the turtle shell in this case. It then calculates the response of those elemental shapes to create the response of the shell as a whole. Twelve load conditions, representing the bite of a predator at different locations, were applied.

The females of both species fared better than the males, although male and female Wood Turtles were more evenly matched. Female shells showed less stress than male shells. The concave shape of the plastron, or underside, of the male Wood Turtle's shell in particular exhibited significantly increased stress, indicating it would be more easily punctured by a predator.

These differences between sexes may stem from selection based on other factors besides predation. Currently, there are no data showing that females are more likely to encounter predators, for instance, and that therefore their shells have become better able to withstand such attacks. However, these variations can have an effect on turtles' lives and offer important implications for turtle conservation efforts.

Full text of the article "Dimorphism in Shell Shape and Strength in Two Species of Emydid Turtle," Herpetologica, Volume 67, Issue 4, November 2011, is available at: http://www.hljournals.org/

Tree-Dwelling Animals Were The First To Fly, New Research Suggests

A six-legged, 25 g robot has been fitted with flapping wings in order to gain an insight into the evolution of early birds and insects.

Published on 18 October, in IOP Publishing’s journal Bioinspiration & Biomimetics, the study showed that although flapping wings significantly increased the speed of running robots, the origin of wings may lie in animals that dwelled in trees rather than on the ground.

The flapping wings increased the speed of the running robot by 90%, going from 0.68 m/s to 1.29 m/s, and also enabled it to climb steeper gradients, increasing from a 5.6° ascent to a 16.9° ascent, which would be important in the development of a hybrid running and flying robot that could have several civilian and military applications.

The researchers, from the University of California, Berkley and the Smithsonian Tropical Research Institute, proposed that testing the wings on robots could provide an insight into how they evolved in early birds.

Fossils of animals closely related to dinosaurs, dating back further than when birds actually emerged, show that feathers were present on all four limbs, suggesting that the original function of wings was to help animals glide when dropping from a height, much like a paper aeroplane.

An alternative theory is that the first wings may have appeared in land-based animals, functioning as a mechanism to increase running speeds and then leading to take-offs and flying thereafter. The aim of this research was to gauge how much of an advantage flapping wings give a running animal.

“By using our robot we can directly determine the performance effects of flapping wings on a running platform as well as gaining a much greater mechanical insight into how the wings are actually working on the robot. We are thus able to look at the performance of the wings directly rather than attempting to build theoretical aerodynamic models based on fossil morphologies that may be overly sensitive to various assumptions”, said Kevin Peterson, lead author of the study.

Read more ...

Females Can Place Limits On Evolution of Attractive Features in Males, Research Shows (Via Herp Digest)

ScienceDaily (Aug. 5, 2011) - Female cognitive ability can limit how melodious or handsome males become over evolutionary time, biologists from The University of Texas at Austin, Louisiana State University Health Sciences Center and the Smithsonian Tropical Research Institute have observed.



Males across the animal world have evolved elaborate traits to attract females, from huge peacock tails to complex bird songs and frog calls. But what keeps them from getting more colorful feathers, longer tails, or more melodious songs? Predators, for one. Increased elaboration can draw predators in, placing an enormous cost to males with these sexy traits.



In a new paper appearing this week in Science, a group of biologists have shown that females themselves can also limit the evolution of increased elaboration.



Studying neotropical túngara frogs, they found that females lose their ability to detect differences in male mating calls as the calls become more elaborate.



"We have shown that the female túngara frog brains have evolved to process some kinds of information and not others," says Mike Ryan, professor of integrative biology at The University of Texas at Austin, "and that this limits the evolution of those signals."



Imagine looking at a group of five oranges next to a group of six. At a glance, you would quickly notice that one group has one more orange than the other. Now, imagine looking at a pile of 100 oranges next to a pile of 101. It would be nearly impossible for you to notice the difference in size (one orange) between those two piles at a glance. This is known as Weber's Law, which states that stimuli are compared based on proportional differences rather than absolute differences (one orange in the case above).



In túngara frogs, males gather en masse to attract female frogs with a call that is made up of a longer "whine" followed by one or more short "chucks."



Through a series of experiments conducted in Panama, Ryan and his collaborators found that females prefer male calls with the most chucks, but their preference was based on the ratio of the number of chucks. As males elaborate their call by adding more chucks, their relative increase in attractiveness decreases due to a perceptual constraint on the part of females.



Male túngara frog calls also attract a predator: the frog eating fringe-lipped bat. To confirm that male song elaboration wasn't limited by these predators, the researchers also studied how the bats respond to additional "chucks" in the male call.



They discovered that hunting bats choose their prey based on chuck number ratio, just as the female frogs do. So, as males elaborate their call by adding chucks, the relative increase in predation risk decreases with each additional chuck.



"What this tells us is that predation risk is unlikely to limit male call evolution," says Karin Akre, lecturer at The University of Texas at Austin. "Instead, it is the females' cognition that limits the evolution of increasing chuck number."



The above story is reprinted from materials provided by University of Texas at Austin,



Journal Reference:

K. L. Akre, H. E. Farris, A. M. Lea, R. A. Page, M. J. Ryan. Signal Perception in Frogs and Bats and the Evolution of Mating Signals. Science, 2011; 333 (6043): 751 DOI: 10.1126/science.1205623

Scientists reveal health benefits of breeding with Neanderthals

Humans rose to dominance across the world after breeding with Neanderthals, according to new research.
Interbreeding between the two species between 65,000 and 90,000 years ago speeded up modern man’s rapid rise to the head of the evolutionary tree, it is claimed.

It was established last year that a small part of the human genome can be traced back to Neanderthals.

But Prof Peter Parham, an expert in immunology at Stanford medical school in California, has now proved how this instilled a “hybrid vigour” in Homo sapiens that allowed them to go on to populate the world.

According to The Sunday Times, crossbreeding provided humans with a ready-mixed cocktail of disease-resistant genes when the species first ventured out of its native Africa.

This, in effect, speeded up man’s global dominance as they did not need to wait for evolution to do the job, it was claimed.

Matt Pope, a senior research fellow in the Department for Archaeologist at University College London, said the latest study presented exciting evidence of man’s relationship with his ancestors.

“If modern humans were getting close enough to share DNA, what else were they sharing?” he told the paper.

“Rather than having to evolve from scratch as they moved out of Africa into Europe and Asia, this interaction would have provided a fast-track to new environments.”

http://www.telegraph.co.uk/science/science-news/8714018/Scientists-reveal-health-benefits-of-breeding-with-Neanderthals.html

Like Humans, Chimps Are Born With Immature Forebrains

ScienceDaily (Aug. 14, 2011) — In both chimpanzees and humans, portions of the brain that are critical for complex cognitive functions, including decision-making, self-awareness and creativity, are immature at birth. But there are important differences, too. Baby chimpanzees don't show the same dramatic increase in the volume of prefrontal white matter in the brain that human infants do.
Those are the conclusions of a study reported in the August 11th Current Biology that is the first to track the development of the chimpanzee brain over time and to make the comparison to humans.
"One of the most marked evolutionary changes underlying human-specific cognitive traits is a greatly enlarged prefrontal cortex," said Tetsuro Matsuzawa of Kyoto University in Japan. "It is also one of the latest-developing brain regions of the cerebrum."

That built-in developmental delay, now shown to be shared with chimps, may provide an extended period of plasticity, allowing both humans and our closest evolutionary cousins to develop complex social interactions, knowledge and skills that are shaped by life experiences, the researchers say.
"Both humans and chimpanzees need to render their neural network and brain function more susceptible to the influence of postnatal experience," Matsuzawa said.

For instance, he added, both chimps and humans enjoy close relationships between infants and adults, as indicated by smiles and mutual gazes. On the other hand, the greater prefrontal expansion in the human brain may contribute to the development of language, complex social interaction and other abilities that are unique to us.

Matsuzawa's team made their discoveries by studying magnetic resonance imaging (MRI) scans of three growing chimpanzees from the age of six months to six years, when chimps reach pre-puberty.
The findings suggest that a less mature and more protracted elaboration of neuronal connections in the prefrontal portion of the developing brain existed in the last common ancestor of chimpanzees and humans. That commonality is in contrast to what has been observed in studies of our more distant ancestors, the macaques.

Matsuzawa says his group is interested in exploring when over the course of evolutionary time this feature of brain development evolved. His team also hopes to explore the comparison between human and chimpanzee brains into young adulthood, noting that the chimpanzees they studied have entered late puberty at 11-years-old.

http://www.sciencedaily.com/releases/2011/08/110811121326.htm

'Super' mouse evolves resistance to most poisons (via Dawn Holloway)

Scientists say that some European house mice have developed resistance to the strongest poisons.


German and Spanish mice have rapidly evolved the trait by breeding with an Algerian species from which they have been separate for over a million years.

The researchers say this type of gene transfer is highly unusual and normally found in plants and bacteria.

The Current Biology report says this process could yield mice resistant to almost any form of pest control.

Warfarin is a drug widely used in medicine as an anti-coagulant to prevent the build-up of harmful blood clots. It works through inhibiting a protein called VKORC1. This protein turns on our ability to produce vitamin K, which is essential for clotting.

Too much warfarin can cause fatal bleeding, and it was this quality that led to its introduction as a pesticide against rats and mice in the 1950s.

But the creatures have been slowly evolving traits to survive warfarin, and pockets of resistant rodents have been found in many different parts of the world.

Now scientists say that German and Spanish mice have found a rapid method of overcoming the threat by cross-breeding with Algerian mice that are, according to the researchers, an entirely different species.

Genetic exchange
Professor Michael Kohn from Rice University in Houston, Texas, led the team of researchers who carried out the work.

"Our study is so special because it involves hybridisation between two species of mouse that are 1.5-3 million years removed from each other.

"Most of the offspring... do not reproduce, they are sterile - but there is a small window, which remains open for genes to be moved from one species to the other, and that's through a few fertile females - so there is a chance to leak genes from one species to another."

Thanks to these few fertile females, the vast majority of mice in Spain and a growing number in Germany have acquired resistance over a very short period of time, although scientists aren't exactly sure when the first genetic exchanges took place.

And while they may not look any different from normal household mice, in their genetic code they now have the ability to survive the strongest chemicals in the pest control armoury.

"There are a lot of genetic barriers between these species of mice, to see them hybridise and transfer genetic material is quite spectacular, to be frank," said Professor Kohn.

The researchers say that increased human travel and population growth are responsible for bringing these mice species together and putting them under evolutionary stress by trying to poison them.

They are concerned that similar human pressures could afford rats both the necessity and the opportunity to breed across species, resulting in rodents that are almost impossible to control.

Evolutionary pressure
"In southeast Asia there are as many as 64 species of rats with many of these co-occurring in the same areas; in South Africa they have discovered a new species of rat that has rapidly moved from southeast Asia and which co-occurs with the other two species.

"I do foresee that many of these rat species will move across the globe - potentially have been moved; we just haven't detected them yet. So the potential for this interbreeding between these closely related rodent species and the exchange of resistance is given more often than it was in the past."

Professor Kohn believes that his research is an example of what scientists call horizontal gene transfer, a process normally seen in bacteria and plants but rarely in animals.

"There have been some accusations that we had oversimplified things by saying this is horizontal gene transfer - I believe that it is. But it is more special than that, because it has to overcome this hurdle of hybrid sterility in the first generation of offspring at the very least."

Other scientists aren't so sure. Dr Julie Dunning Hotopp is from the Institute for Genome Science at the University of Maryland, US. She says the house mouse story does not meet her definition.

"It's interesting work - but I wouldn't call it horizontal gene transfer, which I would say was gene exchange in the absence of sex.

"In many respects I don't think it's surprising, anytime you have a strong pressure like a pesticide, you will have the opportunity to have these changes.

"As humans we are applying more pressure, but we can observe the changes more easily as well thanks to improved genomic sequencing. We will find more examples like this because we can look for more.

But for now at least, the "super mice" have not made it as far as the UK, which Professor Rice thinks is a little odd as Britain was the first place to discover resistance in rats and mice in the 1960s.

"Our mice have not reached the UK as yet, which gives us some idea of how recent this is - but they could be on their way," he said.


By Matt McGrath

Science reporter, BBC World Service

http://www.bbc.co.uk/news/science-environment-14462733

Without Competition, Island Frogs Evolve Rapidly

ScienceDaily (Aug. 1, 2011) — Scientists led by Ben Evans of McMaster University have documented the rapid evolution of new fanged frog species on the island of Sulawesi, near the Philippines.


The team found 13 species of fanged frog on the island, nine of which hadn't previously been described. The species differ in body size, amount of webbing in their feet, and even how they raise their young -- all in accordance with the demands of their distinct ecological niches. Sulawesi has the same number of fanged frog species as the Philippine archipelago.


"We would expect to find more species on the archipelago because it's so much larger, but that's not the case," Evans said.

Why such diversity on the smaller island? There's less competition on Sulawesi, the researchers say. Fanged frogs in the Philippines have to compete with another genus of frogs, Platymantis. Platymantis never made to hop over to Sulawesi, leaving the fanged frogs free to spread out into new habitat niches, to which they eventually adapted. The rapid evolution of these frogs is a striking example of adaptive radiation -- a concept Charles Darwin famously recorded in Galapagos finches.

The research appears in the American Naturalist
http://www.sciencedaily.com/releases/2011/07/110727164711.htm

Ancient dog skull unearthed in Siberia

A very well-preserved 33,000 year old canine skull from a cave in the Siberian Altai mountains shows some of the earliest evidence of dog domestication ever found.

But the specimen raises doubts about early man's loyalty to his new best friend as times got tough.

The findings come from a Russian-led international team of archaeologists.

The skull, from shortly before the peak of the last ice age, is unlike those of modern dogs or wolves.

The study is published in the open access journal Plos One.

Although the snout is similar in size to early, fully domesticated Greenland dogs from 1,000 years ago, its large teeth resemble those of 31,000 year-old wild European wolves.

This indicates a dog in the very early stages of domestication, says evolutionary biologist Dr Susan Crockford, one of the authors on the study.

"The wolves were not deliberately domesticated, the process of making a wolf into a dog was a natural process," explained Dr Crockford of Pacific Identifications, Canada.

But for this to happen required settled early human populations: "At this time, people were hunting animals in large numbers and leaving large piles of bones behind, and that was attracting the wolves," she said.

The most curious, least fearful wolves tended to have more juvenile characteristics with shorter, wider snouts and smaller, more crowded teeth, features that, over generations, came to define the domesticated dog.


These early dogs would have been useful to people in cleaning up scraps and fending off other predators such as bears, but after the ice age, over the last 10,000 years, they became key members of the team, believes Oxford University archaeologist Professor Thomas Higham, a co-author on the study.

"When you've got hunting dogs, all of a sudden it's a game changer. Hunters with dogs are much better than sole hunters," he told BBC News.

Intriguingly though, this much older early Siberian dog seems to have hit an evolutionary dead end. While people continued to occupy the Altai through the depths of the last ice age, they seem to have done so without their dogs, perhaps as food became more scarce.

"What the ice age did was to cause people to move around more," said Dr Crockford, halting the process of domestication and setting wolves and people back into competition for perhaps 20,000 years.

Fortunately, the closest modern dog, the Siberian Samoyed bred to herd and guard reindeer, seems to have taken up where its ancient predecessor left off.

By Hamish Pritchard

Science Reporter

http://www.bbc.co.uk/news/science-environment-14390679

Rapid Venom Evolution in Pit Vipers May Be Defensive; Marsupials That Prey On Venomous Snakes Also Evolve Rapidly (Via HerpDigest)

Rapid Venom Evolution in Pit Vipers May Be Defensive; Marsupials That Prey On Venomous Snakes Also Evolve Rapidly

ScienceDaily (July 20, 2011) - Research published recently in PLoS ONE delivers new insight about rapid toxin evolution in venomous snakes: pitvipers such as rattlesnakes may be engaged in an arms race with opossums, a group of snake-eating American marsupials.

Although some mammals have long been known to eat venomous snakes, this fact has not been factored into previous explanations for the rapid evolution of snake venom. Instead, snake venom is usually seen as a feeding, or trophic, adaptation. But new molecular research on snake-eating opossums by researchers affiliated with the American Museum of Natural History suggests that predators factor into the rapid evolution of snake venom.

"Snake venom toxins evolve incredibly rapidly," says Robert Voss, curator in the Department of Mammalogy at the American Museum of Natural History. "Most herpetologists interpret this as evidence that venom in snakes evolves because of interactions with their prey, but if that were true you would see equally rapid evolution in toxin-targeted molecules of prey species, which has not yet been seen. What we've found is that a venom-targeted protein is evolving rapidly in mammals that eat snakes. That suggests that venom has a defensive as well as a trophic role."

Several groups of mammals are known for their ability to eat venomous snakes, including hedgehogs, mongooses, and some opossums. Opossums, which belong to the marsupial family Didelphidae, consist of about one hundred known and several dozen undescribed species. Most of these opossums live in Central and South America, although there is one representative in the north that is familiar to those who spend time outside at night: the Virginia opossum.

Some didelphids, including the Virginia opossum, are known to eat rattlesnakes, copperheads, and some species of tropical pitvipers known as lanceheads. All of these pitvipers have venom containing dozens of highly toxic compounds, including many that attack blood proteins, causing massive internal hemorrhaging in nonresistant warm-blooded prey species, mainly rodents and birds.

The new research came out of a previous phylogenetic study of marsupials, published as a Bulletin of the American Museum of Natural History, that suggested unusually rapid evolution in one gene among a group of snake-eating opossums. The rapidly evolving gene codes for von Willebrand's factor, an important blood-clotting protein that is known to be the target of several snake-venom toxins. The association of rapid evolution in a venom-targeted gene among just those opossums known to eat pitvipers was the essential clue that prompted further study.

"This finding took us by surprise," says Sharon Jansa, associate professor in the Department of Ecology, Evolution and Behavior at the University of Minnesota and a Museum research associate. "We sequenced several genes -- including the one that codes for von Willebrand Factor (vWF) -- to use in a study of opossum phylogeny. Once we started to analyze the data, vWF was a real outlier. It was evolving much more rapidly than expected in a group of opossums that also, as it turns out, are resistant to pitviper venom."

The recently published research demonstrates that the rate of replacement substitutions (nucleotide changes that result in amino-acid changes) is much higher than the rate of silent substitutions (nucleotide changes that have no effect on the protein) in the von Willebrand Factor gene among pitviper-eating opossums. Typically, high rates of replacement substitutions means that the gene is under strong, sustained natural selection. That only happens in a few evolutionary circumstances.
"Most nucleotide substitutions have little or no effect on protein function, but that doesn't seem to be the case with vWF in these venom-resistant opossums," says Jansa. "The specific amino acids in vWF that interact with toxin proteins show unexpectedly high rates of replacement substitutions. These substitutions undoubtedly affect protein function, suggesting that the vWF protein can no longer be attacked by these snake toxins."

"It is so uncommon to find genes under strong positive selection, that the exceptions are really interesting and often conform to one evolutionary circumstance when two organisms are coevolving with each other," says Voss. "We've known for years that venom genes evolve rapidly in snakes, but the partner in this arms race was unknown until now. Opossums eat snakes because they can."
The National Science Foundation funded this research.

People at darker, higher latitudes evolved bigger eyes and brains

People who live at higher latitudes have larger eyes and more processing power in their brains to deal with visual information compared with those living nearer the equator, a study suggests.

"As you move away from the equator, there's less and less light available, so humans have had to evolve bigger and bigger eyes," said Eiluned Pearce from the Institute of Cognitive and Evolutionary Anthropology at Oxford University, a lead author on the study.

"Their brains also need to be bigger to deal with the extra visual input. Having bigger brains doesn't mean that higher-latitude humans are smarter, it just means they need bigger brains to be able to see well where they live."

This suggests that someone from Greenland and someone from Kenya will have the same ability to discern detail, but the person from the higher latitude needs more brainpower and bigger eyes to deal with the lower light levels.

Professor Robin Dunbar, director of the Institute of Cognitive and Evolutionary Anthropology at Oxford University and a co-author of the study, said that people whose ancestors have lived within the Arctic circle, have eyeballs 20% bigger than people whose ancestors lived near the equator. They have an associated increase in the size of the brain's visual cortex, which previous studies have shown correlates with the size of the eyeball.

Brain volume is known to increase with latitude: people living at high latitudes north and south of the equator have bigger brains than people living near the equator and . Dunbar said that scientists have wondered whether these inherited differences in total brain volume were driven by the pressure to adapt to low light levels at high latitudes.

The researchers measured the brain volumes and eye sockets of 55 skulls kept at the Oxford University Museum of Natural History dating from the 19th century. The skulls represented 12 different populations from around the world, including indigenous people from England, Australia, China, Kenya, Micronesia and Scandinavia.

The results, published on Wednesday in the journal Biology Letters, showed that the biggest brains, averaging 1,484 millilitres, were from Scandinavia, while the smallest brains, around 1,200 millilitres, came from Micronesia. Average eye socket size was 27 millilitres in Scandinavia and 22 millilitres in Micronesia.

Dunbar said the increase in brain volume must have evolved relatively recently in human history. "It's only within the last 10,000 years or so that modern humans have occupied all latitudes right up to the Arctic circle. This is, I guess, an adaptation that's happened within the last 10,000 years."

The researchers controlled for possible confounding variables influencing their data, such as the fact that people who live at higher latitudes are physically bigger and the possibility that the size of a person's eye socket in colder climates might be bigger to allow for a thicker layer of insulating fat.

The results for human eyes mirror those found in birds and non-human primates. Bird species that sing earlier in the dawn chorus at high latitudes have bigger eyes than those that sing later, and nocturnal primates have bigger eyeballs than species that are awake during the day.

Alok Jha, science correspondent

guardian.co.uk

http://www.guardian.co.uk/science/2011/jul/27/higher-latitudes-bigger-eyes-brains