Big brains helped smart mammals survive the last ice age that wiped out megafauna

Various species of megafauna that disappeared at the end of the last ice age. Credit: LifeGate.

The last ice age, which we colloquially call the last ice and which lasted until about 11,500 years ago, caused the extinction of megafauna – multi-ton animals like mastodons and mammoths, as well as fearsome apex predators like saber-toothed tigers and giant wolves. . But many other mammals, including humans, survived.

Scientists have always debated the exact cause of the disappearance of megafauna. An oft-cited explanation is that large animals simply couldn’t find enough calories to support their heavy bodies, but if so, why did huge mammals like elephants, rhinos, and hippos have- did they survive? A new study takes a different view, suggesting that these large mammals may not have had enough brainpower to adapt to their rapidly deteriorating environment.

Outsmart the Ice Age

Researchers from Tel Aviv University and the University of Naples examined data from paleontological records of 50 species of extinct mammals from all continents, weighing from 11 kg (24 pounds), in the case of the giant echidna, up to as much as 11 tons as the straight-tusked elephant. The cranial cavity of these extinct animals has been compared to that of 291 species of near-evolutionary mammals that survived the Ice Age and still exist today.

This analysis showed that surviving mammals have brains that are, on average, 53% larger than extinct species of similar body size. These big-brained mammals may have been better equipped cognitively to withstand the challenges of life during a food-strapped ice age, as well as to better adapt to a new threat posed by humans and their dangerous weapons. .

“We hypothesize that mammals with larger brains were able to adapt their behavior and cope better with changing conditions – primarily human hunting and possibly climate changes that occurred during this time – compared to to mammals with relatively small brains,” said Professor Shai Meiri of Tel. The Aviv University School of Zoology and the Steinhardt Museum of Natural History said in a statement.

In some places, insufficient cognitive resources had a disproportionate effect. While Africa has elephants and hippos, Australia’s largest mammals are red and gray kangaroos (up to 100 times smaller than elephants), while in South America the largest survivors are the llama-sized guanaco and vicuna.

“Previous studies have shown that many species, especially large species, have become extinct due to overhunting by humans entering their habitats. In this study, we tested our hypothesis for mammals over a period of approximately 120,000 years, from the start of the last ice age and when modern humans began to spread weapons around the world. mortals, up to 500 years before our era. . This hypothesis even helps us explain the large number of extinctions in South America and Australia, since the large mammals living on these continents had relatively small brains,” said doctoral student Jacob Dembitzer from the University of Naples in Italy. , who led the study.

The end of the last ice was a time of great changes in climate and habitat. In North America, for example, grasses changed to contain more silica and fewer nutrients, so animals weren’t getting the right kind of food they were used to. As the great ice sheet that covered North America and Europe retreated, it caused well-defined winter and summer seasons, forcing animals to migrate to new ecological zones to adapt. Suddenly, new plants and new terrains created by the new seasons created a new balance in the ecosystem. Those who don’t adapt eventually die.

Although the new findings offer a compelling explanation for the disappearance of iconic Pleistocene megafauna, their extinction is likely due to a confluence of factors. Climate change, overhunting by humans, and new diseases may have played a significant role in the extinction of more than 35 different types of large mammals.

The appearance in the newspaper Scientific reports.


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