Неправда о динозаврах

alexander koryagin написал(а) к All в Apr 16 12:46:20 по местному времени:

Нi,All!

Теория, что причиной вымирания динозавров стал астероид - неправда. По
новым данным главной причиной стало похолодание климата, а численность
динозавров сокращалась в течении десятков миллионов лет до падения
астероида.

http://www.bbc.com/news/science-environment-36073592
-----Beginning of the citation-----
Dinosaurs 'in decline' 50 million years before asteroid strike By Pallab
Ghosh Science correspondent,
BBC News 18 April 2016

The dinosaurs were already in decline 50 million years before the
asteroid strike that finally wiped them out, a study suggests.

The new assessment adds further fuel to a debate on how dinosaurs were
doing when a 10km-wide space rock slammed into Earth 66 million years ago.

A team suggests the creatures were in long-term decline because they
could not cope with the ways Earth was changing.

The study appears in PNAS journal.

Researchers analysed the fossil remains of dinosaurs from the point they
emerged 231 million years ago up to the point they went extinct.

To begin with, new species evolved at an explosive rate. But things
started to slow about 160 million years ago, leading to a decline in the
number of species which commences at about 120 million years ago.

Dr Manabu Sakamoto, a palaeontologist from the University of Reading,
who led the research, said: "We were not expecting this result."

"Even though they were wiped out ultimately by the impact of the
asteroid, they were actually already on their way out around 50 million
years before the asteroid hit."

Mixed pattern

Dr Sakamoto's analysis shows that the long-necked giant sauropod
dinosaurs were declining the fastest, whereas theropods, the group of
dinosaurs that included the iconic Tyrannosaurus rex, were in a more
gradual decline.

Co-author Dr Chris Venditti, an evolutionary biologist from the
University of Reading, told BBC News:

"The current widespread view is that dinosaurs were reigning strong
right up to the impact that hit the Earth - and it's the impact that
drove their final extinction," he said.

"And while that's certainly true, what we found was that they were on
the decline long before that."

Dr Venditti believes that the dinosaurs' 50 million year decline
rendered them even more susceptible to the environmental catastrophe
that followed the asteroid impact.

"If they were reigning strong perhaps they would have fared much better
than they did," he said.

A study two years ago also indicated that some species were in decline,
but only for the last few million years before the asteroid impact. The
new research suggests that the problem began tens of millions of years
earlier and affected a wider range of species.

So why were the dinosaurs in decline? No one knows but one possibility
is an inability to cope with the way the environment was changing.

Evolutionary pressures

Conditions 230 million years ago were perfect for the dinosaurs when
they first emerged, warm and lush from pole to equator.

But as the climate cooled and sea levels shifted, the dinosaurs may have
been subjected to new evolutionary pressures.

Dinosaurs and mammals evolved at about the same time, but the former
dominated the land surface for more than 100 million years.

The asteroid impact is commonly thought to have paved the way for
mammals to take over. But the new study suggests that mammalian
supremacy might have occurred eventually, without a space impact.

Co-author Prof Mike Benton of Bristol University, told BBC News: "World
climates were getting cooler all the time. Dinosaurs rely on quite warm
climates and mammals are better adapted to the cold.

"So there might have been a switch over in any case without the asteroid
impact."
----- The end of the citation -----

Bye,All!
Alexander
--- FIDOGATE 5.1.7ds