Navigation Links
Avian origins: new analysis confirms ancient beginnings
Date:2/5/2008

ANN ARBOR, Mich.---Did modern birds originate around the time of the dinosaurs' demise, or have they been around far longer"

The question is at the center of a sometimes contentious "rocks versus clocks" debate between paleontologists, whose estimates are based on the fossil record, and scientists who use "molecular clock" methods to study evolutionary history.

A new analysis by researchers at the University of Michigan, the University of Chicago, the Centre for Biodiversity Conservation Mexico and Central America, and Boston University offers the strongest molecular evidence yet for an ancient origin of modern birds, suggesting that they arose more than 100 million years ago, not 60 million years ago, as fossils suggest.

The research was published online Jan. 28 in the journal BMC Biology.

"Scientists typically use two sources of information to date biological events: the fossil record, which contains physical remains of ancient organisms, and molecular genetic data," said graduate student Joseph Brown, who is first author on the paper. In the case of modern birds, however, the two approaches have yielded conflicting results, at times leading to heated debates between paleontologists and molecular biologists. Molecular biologists have asserted that the fossil record must be incomplete, while paleontologists have countered that the genetic data must be suspect.

In fact, both approaches have their weaknesses, Brown said. Fossils tend to underestimate how much time has passed since lineages diverged. That's because fossils preserve only evidence of changes in outward physical appearance, and such changes take some time to accumulate after the actual "speciation event" that marks the divergence.

As for genetic data, the so-called molecular clock isn't quite as precise as once thought. The approach relies on the observation that although mutations occur at random in the genome, when looked at over long stretches of time they occur (or "tick") at a fairly constant rate. Molecular biologists use that rate to reconstruct evolutionary history.

"If we know, for example, that DNA sequences diverge by an average of two percent every million years, and we determine that two species differ genetically by ten percent, we can figure out that they last shared a common ancestor five million years ago," Brown said. The problem is, "different lineages can 'tick' at different rates, so applying a single rate to an entire tree could lead to very suspect results."

Fortunately, new methods exist for compensating for differing rates.

"What my colleagues and I did was apply all of these new methods to the problem of the origin of modern birds, with each method making different assumptions about how mutation rate changes across the tree," Brown said. He hoped the analysis would narrow the gap between fossil and molecular data, but in fact it only reinforced the rock-clock split by underscoring the finding that modern birds arose more than 100 million years ago.

So where does that leave the contentious camps of scientists trying to solve the puzzle of how the world's 10,000 bird species came about"

"Rather than fighting across groups, we now have the joint goal of explaining this rock-clock gap," Brown said. "Resolution of the issue will be fertile ground for future research for a while to come."


'/>"/>

Contact: Nancy Ross-Flanigan
rossflan@umich.edu
734-647-1853
University of Michigan
Source:Eurekalert

Related biology news :

1. MIT finds key to avian flu in humans
2. Smiths Detection to launch a portable diagnostic system for foot-and-mouth disease and avian flu
3. New field-deployable biosensor detects avian influenza virus in minutes instead of days
4. Analysis calls for medical device information to better serve patients and doctors
5. More comprehensive analysis of Klamath River basin needed to aid decision makers
6. Human clones: New U.N. analysis lays out worlds choices
7. Powerful integration of lipid metabolic profiling with gene expression analysis
8. Tumor genome analysis unveils new insights into lung cancer
9. Analysis of breast and colon cancer genes finds many areas of differences between tumors
10. Interacting protein theory awaits test from new neutron analysis tools
11. DNA analysis shows true dispersal of protozoa
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/1/2016)... 1, 2016  Today, the first day of American ... to develop a first of its kind workplace health ... Watson. In the first application of Watson ... IBM ), and Welltok will create a new offering ... cognitive analytics, delivered on Welltok,s health optimization platform. The ...
(Date:1/25/2016)...   Unisys Corporation (NYSE: UIS ) today announced ... International Airport, New York City , to help ... to enter the United States using passports ... pilot testing of the system at Dulles last year. The ... during January 2016. --> pilot testing of the ...
(Date:1/21/2016)... 21, 2016 --> ... market research report "Emotion Detection and Recognition Market by Technology ... (Facial Expression, Voice Recognition and Others), Services, Application ... to 2020", published by MarketsandMarkets, the global Emotion ... USD 22.65 Billion by 2020, at a CAGR ...
Breaking Biology News(10 mins):
(Date:2/12/2016)... PLAINFIELD, N.J. , Feb. 12, 2016 /PRNewswire/ ... announced the second annual STRIVE (Strategies to Realize ... Duchenne muscular dystrophy (DMD). STRIVE provides funds to ... programs that will make meaningful contributions to the ... or fostering development of future patient advocates. ...
(Date:2/11/2016)... NBIX ) today announced its financial results for the quarter ... --> For the fourth quarter of 2015, the ... per share, compared to a net loss of $19.4 million, or ... the year ended December 31, 2015, the Company reported a net ... to a net loss of $60.5 million, or $0.81 loss per ...
(Date:2/11/2016)... , Feb. 11, 2016  Bioethics International, a not-for-profit organization ... researched, developed, marketed and made accessible to patients around the ... had named the publication of the Good Pharma ... publication is also featured as one of BMJ Open ... last year that are most frequently read. Ed ...
(Date:2/11/2016)... ... February 11, 2016 , ... ... dedicated to delivering cutting-edge information focused on the development and manufacture of ... become a premier sponsor of the 2016 BioProcess International Awards – Recognizing ...
Breaking Biology Technology: