Fifty-six million years ago, about ten million years after the dinosaurs became extinct, our planet has experienced something strange. It was hot. Very hot. As hot as you used long ago for several billion years before that. Carbon signatures in geological records have shown that global temperatures jumped by 5-8 degrees Celsius over 10,000 years.
They also indicate that the temperature of the planet remained elevated 17 000 years before has returned to its normal level. Scientists call this relatively rapid temperature rise "hyperthermal event", and it was not the only one since then.
Two million years the Earth experienced another rise in the temperature, which was two times weaker than the predecessor. Throughout Earth's history there were other smaller hyperthermal events. Most scientists agree that we are now experiencing one of these.
Abigail D'ambrosia, a graduate of the University of new Hampshire, seeks to answer the question: what happens to living things when rising global temperatures?
They are dying? Adapt? Change at all?
The study, published last week in the journal Science Advances, indicates that at least some mammals are decreasing in size. And how much they decrease is directly related to the temperature of the planet.
The Findings are based on a new analysis of fossilized teeth and jaw fragments, collected in the bighorn basin in northwestern Wyoming, 120 miles from Yellowstone national Park.
"In the case with older mammals, the measurement of the teeth gives an indication of the size of their bodies," says D'ambrosia.
Comparing the changes in tooth size within a single species over time, scientists were able to show that the reduction in mammals occurred during the largest events warming about 56 million years ago.
In particular, they showed that the first animal species Sifrhippus decreased by 30% during the first 130,000 years of warming. As global temperatures slowly returned to normal, the size of their bodies again increased by 76%. D'ambrosia asked a question, was there a similar decrease during the smaller warming of about 54 million years ago.
To find out, she set to work on collecting and measuring the four teeth of mammals that lived before and during this period.
In her study included Arenahippus pernix (early horse the size of a small dog), Diacodexis metsiacus (predecessor of pigs and deer-sized rabbit), Hyopsodus simplex (herbivore the size of a weasel) and Cantius abditus (early primates similar to modern lemurs).
D’Ambrosia says that in the case of young horse, the difference in teeth size between individual animals that lived before the period of warming after the obvious.
"It's very interesting," she says. "When I first started to take measurements, my consultant started randomly grabbing teeth and tried to guess which came from hyperthermal of the period. It was possible to determine, even visually".
And you can too.
Scientific analysis of the data showed that during the second event warming Arenahippus decreased in size by 14% — that is, the size of the dog to the size of a cat.
These findings suggest that the response of the size reduction on the temperature increase is proportional to the magnitude of warming. During the first warming event the little horse has decreased by 30%. During the second warming, which was two times the amount, another small horse decreased by 14%.
D Ragweed was less than the teeth from the other three species included in the study, but it could still determine that Diacodexis, the predecessor of the deer showed a decrease of 15%. Resize Hyopsodus herbivores were minor (4%), and the Primate Cantius generally overturned this trend, showing a 2 percent growth. However, the last two results is not indicative, as the samples were not so much.
Although reductions in the face of climate change may seem a strange answer, in scientific circles it is well known that mammals become less in a warmer climate. For example, red foxes who live in higher and colder latitudes, become larger, if you live closer to the equator. This phenomenon even has a name — the Bergman's rule.
"the Idea that cool little body more efficient, since the ratio of area to volume is higher," says the scientist.
This ratio allows smaller animals produce more heat and more animal — to keep heat to a cooler environment. And all animals that survived the ancient hyperthermal events could be reduced for other reasons, including not being able to get enough water or food. And since the planet is getting warmer today, scientists can clearly observe the response of mammals.
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