October 22, 2021

Beyond Going Long

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There was a terrible mass extinction 30 million years ago, and we just noticed it

The end of the Eocenian era about 33 million years ago was a period of great change on Earth. In a slow reversal of what we see today, temperatures have fallen and finger-ice glaciers have stretched toward the equator.

loss of life It was deep in the Asian continent. However, Africa’s biodiversity, protected by heat in the tropics, does not appear to have been affected by the dramatic changes. Or so we thought.

According to a study recently published by a team of scientists from across the USA, we did not look at the fossil record in the right way.

Research indicates that mammals in the Arabian Peninsula and the African continent did not thrive during this cold change, but experienced a dramatic decline, with nearly two-thirds of their maximum diversity disappearing 30 million years ago.

It is not clear what exactly led to the individual losses, although the extreme temperature fluctuations and intense volcanic activity that rocked the regions, there is no shortage of possibilities.

Whatever the cause of the loss, the ecological gaps they left after the extinction were not empty for long.

“It’s quite clear that there was a huge extinction event and then a recovery period” He says Duke University biologist Stephen Heritage.

Much of what we know about climate change during the transition from the Eocene to the following epoch, the Oligocene, comes from analyzes of changes in oxygen isotopes in sediment cores extracted from the ocean floor.

Combining this evidence with various other evidence for sea level fluctuations and evidence for glacier growth gives us an overall picture of how our planet as a whole is changing.

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However, labeling at the local level may be a bit incoherent, relying more on modeling and careful examination of the fossils, which appear sporadically there.

Records taken from Earth can present a mixed picture, so it is not surprising to discuss the ultimate impact of global cooling on masses near the equator.

from the direction There is a clue They are animals like the ancestors of modern lemurs, which are disappearing from northeastern Africa. After more studies This indicates that Africa has experienced virtually no, or perhaps no, environmental change.

Interpreting fossil records can be difficult because they tend to be somewhat uneven. Not all species leave their remains neatly stored in the right place, but with the right analytical tools, scientists can still retrieve a wealth of information from just a few bones.

The team collected data on fossils representing five groups of mammals, including the so-called carnivores HinodontsTwo groups of rodents look like a squirrel abnormality, and two groups of primates – one occupied by our ancestors.

From these samples, the researchers came up with ratios representing the timing of manifestations and known losses for each. Statistical tools can then give scientists a better idea of ​​when losses in certain regions were large enough to correlate with global events.

By looking at characteristics in related groups, scientists can also see how species diversified to fill the niches released by the lost animals.

Take animal teeth, for example. The nuances of their shapes over a long period of time can tell us how quickly a species has adapted to a newly rich food source.

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“We see a significant loss of tooth diversity and then a period of renewal with new tooth shapes and new changes,” He says Lead author Dorian de Vries of the University of Salford.

By the way, it seems that our main ancestors are among the most affected. The diversity of human teeth has declined to nearly 30 million years ago. It was so bad that there was only one type of dental morphology left, which limited the types of food their grandchildren could eat.

Such bottlenecks are common throughout the evolutionary record. Knowing how species respond to them can be vital given the pressure we place on many ecosystems around the world today.

In a sense, the dental design succeeded. If not, our species would not see the light of day.

“It was a real reset button” He says Devries.

This research was published in Communication biology.