-Caveat Lector-
Begin forwarded message:
From: [EMAIL PROTECTED]
Date: March 28, 2007 11:56:58 AM PDT
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED]
Subject: Mutants vs Adaptors
DINOSAUR DEMISE DIDN’T SPUR EVOLUTION
IN ANCESTORS OF TODAY’S MAMMALS, STUDY SAYS
Associated Press, March 28, 2007 - Updated: 01:51 PM EST
http://news.bostonherald.com/national/view.bg?articleid=191362
NEW YORK -- The big dinosaur extinction of 65 million years ago
didn’t produce a flurry of new species in the ancestry of modern
mammals after all, says a huge study that challenges a long-
standing theory.
Scientists who constructed a massive evolutionary family tree
for mammals found no sign of such a burst of new species at that
time among the ancestors of present-day animals.
Only mammals with no modern-day descendants showed that effect.
”I was flabbergasted,” said study co-author Ross MacPhee,
curator of vertebrate zoology at the American Museum of Natural
History in New York.
At the time of the dinosaur demise, mammals were small, ranging
in size between shrews and cats. The long-held view has been that
once the dinosaurs were gone, mammals were suddenly free to exploit
new food sources and habitats, and as a result they produced a
burst of new species.
The new study says that happened to some extent, but that the
[mutated] species led to evolutionary dead ends. In contrast, no
such burst was found for the ancestors of modern-day mammals like
rodents, cats, horses, elephants and people.
Instead, they showed an initial burst between 100 million about
85 million years ago, with another between about 55 million and 35
million year ago, researchers report in Thursday’s issue of the
journal Nature.
The timing of that first period of evolutionary development
generally agrees with the conclusions of some previous studies of
mammal DNA, which argue for a much earlier origin of some mammal
lineages than the fossil record does.
The second burst had shown up in the fossil record, MacPhee
said. But he said the new study explains why scientists have been
unable to find relatively modern-looking ancestors of the creatures
known from that time: without any evolutionary boost from the
dinosaur demise, those ancestors were still relatively primitive.
Some experts praised the large scale of the new evolutionary
tree, which used a controversial ”supertree” method to combine data
covering the vast majority of mammal species. It challenges
paleontologists to find new fossils that can shed light on mammal
history, said Greg Wilson, curator of vertebrate paleontology at
the Denver Museum of Nature & Science.
William J. Murphy of Texas A&M University, who is working on a
similar project, said no previous analysis had included so many
mammal species.
But, ”I don’t think this is the final word,” he said.
The study’s approach for assigning dates was relatively crude,
he said, and some dates it produced for particular lineages
disagree with those obtained by more updated methods.
So as for its interpretation of what happened when the
dinosaurs died off, ”I’m not sure that conclusion is well-founded,”
Murphy said.
John Gittleman, a study co-author and director of the
University of Georgia Institute of Ecology, said the researchers
considered a range of previously reported dates for when various
lineages split. They found the overall conclusions of the study
were not significantly affected by which dates they chose, he said.
Researchers should now look at such things as the rise of
flowering plants and a cooling of the worldwide climate to explain
why ancestors of present-day mammals took off before the dinosaurs
died out, Gittleman said. The cause of the later boom is also a
mystery, he said.
The study’s family tree includes 4,510 species, more than 99
percent of mammal species covered by an authoritative listing
published in 1993. (Nearly 300 species have since been added to the
listing, but the researchers said that doesn’t affect their study’s
conclusions.) To construct it, the researchers combined previously
published work that relied on analysis of DNA, fossils, anatomy and
other information.
S. Blair Hedges, an evolutionary biologist at Pennsylvania
State University, said the new work ”pushes the envelope in the
methods and data, and that’s really important.”
He said the demise of the dinosaurs may have affected mammal
evolution by influencing characteristics like body size rather than
boosting the number of new species created. Such changes wouldn’t
be picked up by the new study, he noted.
AOL now offers free email to everyone. Find out more about what's
free from AOL at AOL.com.
www.ctrl.org
DECLARATION & DISCLAIMER
==========
CTRL is a discussion & informational exchange list. Proselytizing propagandic
screeds are unwelcomed. Substance—not soap-boxing—please! These are
sordid matters and 'conspiracy theory'—with its many half-truths, mis-
directions and outright frauds—is used politically by different groups with
major and minor effects spread throughout the spectrum of time and thought.
That being said, CTRLgives no endorsement to the validity of posts, and
always suggests to readers; be wary of what you read. CTRL gives no
credence to Holocaust denial and nazi's need not apply.
Let us please be civil and as always, Caveat Lector.
========================================================================
Archives Available at:
http://www.mail-archive.com/ctrl@listserv.aol.com/
<A HREF="http://www.mail-archive.com/ctrl@listserv.aol.com/">ctrl</A>
========================================================================
To subscribe to Conspiracy Theory Research List[CTRL] send email:
SUBSCRIBE CTRL [to:] [EMAIL PROTECTED]
To UNsubscribe to Conspiracy Theory Research List[CTRL] send email:
SIGNOFF CTRL [to:] [EMAIL PROTECTED]
Om