Conflict about the origin of birds

The new study suggests that birds today date back to 100 million years ago - a long time before dinosaurs became extinct.

In the search for the ancestors of modern birds, studies have shown conflicting results of fossils and genetic analysis. Fossil studies suggest that modern birds originated 60 million years ago, after the Cretaceous period ended 65 million years ago, also the period of dinosaurs extinction.

But molecular studies suggest that the genetic differences of many bird species occur during the Cretaceous period. And a new molecular-based study suggests that the ancestor of this species appeared 40 million years earlier than the proposed time. In this work, scientists apply a new method: studying the rate of variation among groups of species.

A pair of red South American macaws fly over Madidi National Park in Bolivia.According to a new genetic study, modern birds can originate from 100 million hundred now, long before the dinosaurs became extinct.(Photo: Joel Satore / NGS)

"The purpose of the study is to give a definitive answer to conclusions from two sources of information," said Joseph Brown, lead researcher and doctoral student at Michigan University in Ann Arbor .

New research has been published in BMC Biology .

Methods of dating

When it comes to dating the biological events, molecular geneticists rely on a theory of molecular clock names. After long periods of time, variation occurs at a fairly regular frequency. By measuring the degree of genetic variation, scientists can assess at what time in the past the branched species.

In groups with distant families, such as different families or birds, the molecular clock is 'more unusual ' than people think. Perhaps this is because different lines of birds can mutate at different frequencies, so applying a single speed to them may lead to unreliable results.

The way of evaluation is improved

The work is the first close investigation of the possibility of poor assumptions about bird genetic data leading to differences of up to 50 or 60 million years between fossil and genetic testing.

The most likely explanation is that these two sources of information deal with different periods of diversification.

Genetic data is used during the period when the genomes share a common ancestor, which can be pushed up earlier than the development of new species. And fossils only record the product of evolution.

Patrick O'Connor, a paleontologist at Ohio University, Athens, said: 'One important point to emphasize is that these data are not necessarily more reliable than fossils. The information we get from fossils and animals today is an additional set of facts that we should incorporate into the research process compared to today. '

Patrick also added: 'The work encourages paleontologists to continue searching for fossils of modern birds in the Cretaceous stage. The important thing here is that there are fossils supporting the evolutionary view of bird evolution. This work has corroborated some recent findings. '