The skeleton in an iron-toothed cat
Christickphotographotography / Saturation
Studies of thousands of fossils from La Brea Breas in California have not found evidence of any species Progress in response In falling temperatures such as ice sheets spread on the continent, or later warming when glacial period ends.
“They did not change the climate change as many biologists believe everyone should do,” as Donald Protonero In California State Polytechnic University in Pomona. “They are static, in spite of evident evidence of climate change in 20,000 years ago.”
While Charles Darwin thinks that evolution slowly and gradually, it’s obvious that it Always loudly. there More examplesfrom rats and Bedbugs changed pesticide resistance UNTO Owls who get browner as snow can be less common.
However the fossils were shown that many types remained unchanged in millions of years. It may be that the strong evolution seen in living animals is not usually in addition to large, long changes because it keeps turning off the direction – in other words, that Evolution is no longer immediate.
The fossil record is usually less attempting to it. But in La Brea, ten thousand animals were kept in tar holes in a short period – in the past 50,000 years. Over a million fossil bones have been healed.
At this time, conditions are cooled to the gloomy maximum About 20,000 years ago, then began to warm again. Protonero thinks animals should succeed in dealing with more cold situations by developing larger bodies and somewhat wider animals that help in the cooler regions today.
He and his colleagues looked at fossils 28 birds and seven mymal species, measured the size of adult bones and the ratio of thickened length of the foot bones. Mammals include consumed wild horses, camels, Cats Toothat and American lions, as well as Bison, Cougars and Lynx. Birds are mostly predators like eagles and condors.
The average size and the length of the body’s limb rises and falls in a little while, but no reason to change 20,000 years ago, Protony told a recent meeting of European Geosciencs Union In Vienna, Austria. “The things that happened in times when biologists were familiar with good, very different from what happened in a 10,000-year time,” we said here, “he said.
“We don’t see is the kind of adaptation that people think that the finches of Galapagos represent the world,” as Prototok, refers to Famous studies showing strong evolutionary change in these birds.
In response to his findings, some biologists were targeted that many animals were like condors and bids had many parts of climate change, as Proton. Small animals are the raser of La Brea, but the team returns and watches three little birds – crows, meats and meadowlarks – with the same results.
“Even the smallest birds we can get good samples for not responding to the climate in a way they should,” Protonero said.
She said we never know why the expected evolution changes do not seem to happen. “I still don’t have a good answer why we have stasis.”
Andrew Hendry At Canada’s McGill University focuses outweight in many of La Breas, they still provide occasional snapshots than a detailed picture of changes in years or centuries. “Contemporary evolution is a ton of recurring peaks,” he said. “If you have good data for La Brea, that’s exactly what you can see.”
“The greater changes require the new tight end a place very different from the previous one,” Hendry said. “Large transfers are less common and never get to the fossil record.”
“I don’t think fossil patterns found in talk talk or paper are in changes in changes in attitudes found in corresponding times,” as Michael Kinnison at the University of Maine. “There is no general supposition that the contemporary evolution should take long direction of evolution or speciation.”
Also shown by studies of living animals that coldest situations do not always associate with the greater greater bodies, as Kinnison, so it should always be questionable.
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