From our 21st century perspective, it is almost impossible to do the imaginative exercise necessary to understand what the world was like 10,000 years ago, at the end of the Ice Age. Among other things, it was a world full of gigantic critters (at least by our standards), the so-called Pleistocene megafauna. The vast majority of the world’s large mammals and birds (arbitrarily defined as animals weighing 50 kg or more) kicked off at this time. And we are still far from knowing the details of how it happened. A new study is trying to add another piece to this puzzle, proposing that part of these critters’ vulnerability to extinction has to do with their relative brain size.
The scientific article detailing this hypothesis has just appeared in the specialized journal Scientific Reports, signed by Jacob Dembitzer, from Tel Aviv University in Israel, together with Italian colleagues from Frederick 2 University.O from Naples. They compared brain reconstructions of 50 extinct species of mammals with those of nearly 300 species today to reach that conclusion.
Before detailing the results a little more, however, it is worth highlighting a few more elements of the Pleistocene extinction background. What is clear, first of all, is that she was highly selective from a size perspective: the bigger the critter, the greater the chance of disappearing. It makes sense when we consider that larger animals have a longer gestation period (if they are mammals), longer intervals between pregnancies and generate fewer offspring in each reproductive cycle. That is, environmental disturbances, new predators, etc. tend to affect the chance that monsters will continue to reproduce more. A pup eaten is very, very difficult to replace.
Another essential point is that the megafauna of the Americas and Oceania (and also that of the African island of Madagascar) took much more blows on the back than, in descending order, those of Eurasia and Africa. Scenes from today’s African savannas, full of large herbivores and carnivores, were common in Brazil 10,000 years ago. South America had a higher proportion of mammals weighing over a ton (among giant sloths, relatives of elephants and super armadillos) than Africa.
As both the Americas and Oceania (in the first place, in this case, Australia and New Guinea) only gained human inhabitants in the Ice Age, there is great suspicion that the hunting practiced by our species has pushed the megafauna of such continents. to the abyss. In practice, the matter is controversial, as this report of my authorship shows; the brutal climatic changes of that era may also have been important, or there may (indeed, even must) have been a synergy between these factors.
Returning to the new study: Dembitzer and his colleagues showed, as expected, that body size is one of the factors linked to megafauna extinction risk. However, they also found that today’s surviving mammals have brains up to 83% larger than those of similarly sized extinct species (depending on the statistical method used, the number goes up to 53%, still quite significant).
Their proposed explanation is that the larger brain size could have given its carriers more flexible behavior and greater ability to escape human predators or cope with large-scale environmental changes.
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