Extinct species had, on average, far smaller brains than those that survived, according to research from Tel Aviv University and the University of Naples that looked at the widespread extinction of huge creatures over the past tens of thousands of years.
The researchers conclude that a large brain, which indicates relatively high intelligence in comparison to other species of animals, helped the extant species adapt to changing conditions and cope with human activities like hunting, which has been a major cause of extinction. The researchers link the size of the brain (in relation to the body size of each species) to intelligence.
Professor Shai Meiri of Tel Aviv University’s School of Zoology and the Steinhardt Museum of Natural History, along with Professor Pasquale Raia and doctorate student Silvia Castiglione of the University of Naples in Italy, served as the study’s principal investigators. Scientific Reports, a journal, published the study.
The widespread demise of massive and giant creatures throughout all of earth’s (except Antarctica) continents during the previous Ice Age, according to academics, is what made it distinctive.
There were mastodons, a ton-sized armadillo, and huge ground sloths in America; a ton-sized marsupial called a diprotodon, giant kangaroos, and a marsupial “lion” in Australia; and massive deer, woolly rhinoceros, mammoths, and elephants, some weighing up to 11 tons, in Eurasia.
We found that the surviving animals had brains 53% larger, on average than evolutionarily closely related, extinct species of a similar body size. We hypothesize that mammals with larger brains have been able to adapt their behavior and cope better with the changing conditions mainly human hunting and possibly climate changes that occurred during that period compared to mammals with relatively small brains.
Professor Shai Meiri
However, certain huge creatures, including elephants, rhinos, and hippos, managed to survive and are still alive today. The researchers also point out that in some regions, the extinction was particularly widespread; in Australia, the red and grey kangaroos are currently the biggest native animals, and in South America, the largest survivors are the guanaco and vicua (an animal similar to the domesticated llama), as well as the tapir, while many species that weighed half a ton or more have gone extinct.
Jacob Dembitzer: “We know that most of the extinctions were of large animals, and yet it is not clear what distinguishes the large extant species from those that went extinct. We hypothesized that behavioral flexibility, made possible by a large brain in relation to body size, gave the surviving species an evolutionary advantage it has allowed them to adapt to the changes that have taken place over the last tens of thousands of years, including climate change and the appearance of humans.”
“Previous studies have shown that many species, especially large species, went extinct due to over-hunting by humans that have entered their habitats. In this study, we tested our hypothesis for mammals over a period of about 120,000 years, from the time the last Ice Age began, and the time that modern man began to spread all over the world with lethal weapons, to 500 years before our time. 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.”
The scientists gathered information from the paleontological literature on 50 extinct mammal species from all continents, ranging in weight from 11 kg (an extinct giant echidna) to 11 tons (the straight-tusked elephant, which was also discovered in the land of Israel), and compared the size of their cranial cavity to that of 291 evolutionarily close mammal species that survived and are still alive today, ranging in weight from 1.4 kg (the platypus) to 4 (the African elephant).
They entered the information into statistical models that weighted body size and phylogeny of various species.
Prof. Meiri: “We found that the surviving animals had brains 53% larger, on average than evolutionarily closely related, extinct species of a similar body size. We hypothesize that mammals with larger brains have been able to adapt their behavior and cope better with the changing conditions mainly human hunting and possibly climate changes that occurred during that period compared to mammals with relatively small brains.”
