Does DNA remember?

Can evolution run BACKWARDS? Birds found to regrow bone previously discarded by dinosaurs 230 million years ago

• Scientists have found that birds regrew a bone known as the 'pisiform'
• It disappeared from the biology of two-legged dinosaurs when they no longer needed strong wrists
• However when dinosaurs evolved into birds the bone reappeared
• The new bone is known as the ulnare and is in the same position
• It suggests the effects of evolution can be reversible

In 1890 Belgian palaeontologist Louis Dollo postulated that evolution could not run backwards - something widely accepted by the scientific community.

But now a study has claimed that the changes induced by evolution can be reversible, meaning certain animals can return to an earlier biological trait.

The remarkable discovery was made by finding birds had regrown a bone previously discarded by dinosaurs millions of years ago.

They found that 230 million years ago, two-legged dinosaurs no longer required the strong wrists of their four-legged brethren, and thus they became weak.
The number of bones in wrists shrank from 11 to three, with one in particular of interest to disappear being the pisiform.

But according to research by Dr Vargas, the bone reappeared when dinosaurs evolved into birds and took flight.

The new bone, called the ulnare, appears in the same place as the pisiform once did.
The pisiform allowed bird wings to remain rigid on the upstroke. The study found it disappeared in bird-like dinosaurs, but modern birds later evolved to once again use this tiny bone.
'This idea that a bone can disappear and reappear in evolution has been resisted a lot in evolutionary biology,' Dr Vargas previously told Stephanie Pappas at LiveScience.

Scientists don't know how these bones disappeared, though. Professor Vargas said part of the problem is that palaeontologists look at fossils, while biologists focus on embryos.

But his team brought the research together by looking at fossils as well as studying bird anatomy.
The team also traced certain proteins in 3D embryonic skeletons that were linked to the creation of collagen, which makes up connective tissue.

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New Family Tree Illuminates 'Big Bang' in Bird Evolution After Dinosaur Extinction

A massive genetics project has produced the most comprehensive bird family tree ever, an embarrassment of scientific riches for studying everything from how birds evolved so quickly after dinosaurs disappeared to the ways in which birds and people learn.

The biggest takeaway from the eight studies published Thursday in the journal Science is the way genetic codes can be used to answer wide-ranging questions. Scientists are using birds' DNA, for instance, both for research on the brain and learning and to reconstruct what an ancient ancestor of birds and dinosaurs might have looked like.

Researchers mapped the complete set of DNA instructions, or genomes, of 45 bird species representing every group of living birds, as well as representatives of all three groups of crocodilians—the closest living bird relatives. To produce the new family tree, scientists combined this information with previously published sequences for zebra finches and domestic turkeys and chickens.

Most of our notions of how DNA evolves over time come from studying the genetic instruction books of mammals, says Ed Green, a genome scientist at the University of California, Santa Cruz.

Adding the genomes of birds and crocodilians—the American alligator, saltwater crocodile, and Indian gharial—now allows scientists to better understand how these groups are related, he says.

The new study finds the rate of change in birds' DNA took off 66 million years ago when most dinosaurs went extinct. The surviving dinosaurs then radiated into a constellation of species that led to about 95 percent of birds on the planet today, says Erich Jarvis, a neurobiologist at Duke University in Durham, North Carolina. (See how "Birds Evolved From Dinosaurs Slowly—Then Took Off.")

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