Genetic Researchers Grow A Fish That Has Legs

The fossil record has a lot of strange stories to tell about the evolution of life on Earth, and one of the strangest is how life moved from sea to land. Though clues from the record give the rough outlines of the story—limbs grew from fins in a series of stages in which fins grew longer and narrower—scientists are still filling in the details, trying to determine what genetic changes might have allowed the limbs to grow.

One of the best ways to learn those details is to reproduce the changes that occurred some 400 million years ago—to virtually back in time and alter the development of the land-goer’s living ancestors and see what happens.

Which is what biologist Renata Freitas and colleagues were up to when they added some extra Hoxd13—a gene known to play a role in distinguishing body parts during embryological development— to the tip of a zebrafish embryo’s fin, and watched as the developing fin kept growing.

Their lab findings led the researchers to hypothesize that the secret to limb development may have been a new element in some lobe-finned fish’s DNA. When present, this DNA element would have helped turn on the Hoxd13 gene on the fish embryo’s fins, leading them to lengthen and grow into limbs.

OneZoom: A Fractal Explorer for the Tree of Life

Our knowledge of the tree of life—a phylogenetic tree summarizing the evolutionary relationships among all life on Earth—is expanding rapidly. “Mega-trees” with millions of tips (species) are expected to appear imminently (for example, see http://www.opentree.wikispaces.com). Unfortunately, there has so far been no practical and intuitive way to explore even the much smaller trees with thousands of tips that are now being routinely produced. Without a way to view megatrees, these wondrous objects, representing the culmination of decades of scientific effort, cannot be fully appreciated. The field really needs a solution to this problem to enable scientists to communicate important evolutionary concepts and data effectively, both to each other and to the general public.

Just like Google Earth changed the way people look at geography, a sophisticated tree of life browser could really change the way we look at the life around us … Our advances in understanding evolution are moving really fast now, but the tools for looking at these big trees are lagging behind. (Westneat, February 2009)

Displaying large trees is a hard problem that has so far resisted solution. We are still waiting for the equivalent of a Google Maps. (Page, June 2012)

In this manuscript, we introduce a new approach that solves the problem. Trees with millions of tips, richly embellished with additional data, can now be easily explored within the web browser of any modern hardware with a zooming user interface similar to that used in Google Maps.

'Tree of life' constructed for all living bird species

Scientists have mapped the evolutionary relationships among all 9,993 of the world’s known living bird species. The study, published today in Nature, is an ambitious project that uses DNA-sequence data to create a phylogenetic tree — a branching map of evolutionary relationships among species — that also links global bird speciation rates across space and time.

“This is the first dated tree of life for a class of species this size to be put on a global map,” says study co-author Walter Jetz, an evolutionary biologist at Yale University in New Haven, Connecticut.

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New study sheds light on how and when vision evolved

Opsins, the light-sensitive proteins key to vision, may have evolved earlier and undergone fewer genetic changes than previously believed, according to a new study from the National University of Ireland Maynooth and the University of Bristol published in Proceedings of the National Academy of Sciences (PNAS) .

The study, which used computer modelling to provide a detailed picture of how and when opsins evolved, sheds light on the origin of sight in animals, including humans. The evolutionary origins of vision remain hotly debated, partly due to inconsistent reports of phylogenetic relationships among the earliest opsin-possessing animals.

Dr Davide Pisani of Bristol’s School of Earth Sciences and colleagues at NUI Maynooth performed a computational analysis to test every hypothesis of opsin evolution proposed to date. The analysis incorporated all available genomic information from all relevant animal lineages, including a newly sequenced group of sponges (Oscarella carmela) and the Cnidarians, a group of animals thought to have possessed the world’s earliest eyes.

Using this information, the researchers developed a timeline with an opsin ancestor common to all groups appearing some 700 million years ago. This opsin was considered ‘blind’ yet underwent key genetic changes over the span of 11 million years that conveyed the ability to detect light.

Dr Pisani said: “The great relevance of our study is that we traced the earliest origin of vision and we found that it originated only once in animals. This is an astonishing discovery because it implies that our study uncovered, in consequence, how and when vision evolved in humans.”

(Image credit: Roland Bircher)

Evolution Mostly Driven by Brawn, Not Brains, Analysis Finds

The most common measure of intelligence in animals, brain size relative to body size, may not be as dependent on evolutionary selection on the brain as previously thought, according to a new analysis by scientists.

Brain size relative to body size has been used by generations of scientists to predict an animal’s intelligence. For example, although the human brain is not the largest in the animal kingdom in terms of volume or mass, it is exceptionally large considering our moderate body mass.

Now, a study by a team of scientists at UCL, the University of Konstanz, and the Max Planck Institute of Ornithology has found that the relationship between the two traits is driven by different evolutionary mechanisms in different animals.

Crucially, researchers have found that the most significant factor in determining relative brain size is often evolutionary pressure on body size, and not brain size. For example, the evolutionary history of bats reveals they decreased body size much faster than brain size, leading to an increase in relative brain size. As a result, small bats were able to evolve improved flying maneuvrability while maintaining the brainpower to handle foraging in cluttered environments.

This shows that relative brain size can not be used unequivocally as evidence of selection for intelligence. The study is published in the Proceedings of the National Academy of Sciences.

How do language families evolve over many thousands of years? How stable over time are structural features of languages? Dan Dediu and Stephen Levinson from the Max Planck Institute for Psycholingustics in Nijmegen introduced a new method using Bayesian phylogenetic approaches to analyse the evolution of structural features in more than 50 language families. Their paper ‘Abstract profiles of structural stability point to universal tendencies, family-specific factors, and ancient connections between languages’ was published online on September 20, 2012 in PLoS ONE.