Energetics-based model by Israeli researchers ties up more loose ends, including the extinction of alternative humans and our embrace of a dangerous wild animal in the world's first joint venture

Once upon a time, giant animals walked the earth: sloths as tall as a building, elephants that make today's look like children, woolly rhinoceroses that towered over the puny humans. Once there were other species of humans too.

Most of the large animals and all the other human species are gone and much research has focused on our contribution to that – particularly to the Late Quaternary Megafaunal Extinction that began 50,000 years ago.

But no attention was directed to how the Late Quaternary Megafaunal Extinction affected the humans themselves, or to put it otherwise, how the humans whose contribution to the LQME had been so central affected themselves, point out Miki Ben-Dor and Ran Barkai of Tel Aviv University.

Having continued to wipe out most of the megafauna on which we relied, having reduced the average body mass of terrestrial animals by 98 percent in the space of a million and a half years, how did Homo sapiens not only cope, but conquer the planet? This is the question that Ben-Dor and Barkai address in their latest paper published last week in the science journal Quaternary Environments and Humans.

The answer lies in the identical timing of the final extinctions and the "Upper Paleolithic Revolution," an explosion of innovation and cultural changes that helped us overcome and obtain the smaller, fleeter animals we were reduced to eating.

We know this because we find evidence of host of game-changing developments in the Upper Paleolithic, over the last 50,000 years: the extinction of the Neanderthal, the emergence of better projectile technology (arrows – a better way to hunt a flying bird or leaping hare than throwing a spear); human expansion to hitherto pristine lands, such as Australia and much later, the Americas; accelerated cultural change as evidenced by explosion of art – and –

And allying with the dog. We domesticated wolves and created "man's best friend," thousands upon thousands of years before we domesticated any other animals or any plants.

An enormous amount of research has gone into the domestication of the dog: Who exactly was domesticated? By whom? When? Where? How? Why? But no attention had been directed to the dog's contribution to the story of human evolution.

Fido – or in his earlier incarnation, Fang – isn't the centerpiece of the academic paper. He is just one of the adaptations our species experienced but there he is, barking and shedding on sofas worldwide, integral to the package that begat modern humanity from the people struggling to make do as the megafauna died out.

Corgi decked out in Labubus making do at a two-day Corgi race and costume contest, Lithuania Credit: Petras Malukas / AFP

To be human

Though humanity manfully resists the notion that we wiped out the megafauna, Ben-Dor, Barkai and few other like-minded researchers have demonstrated our significant contribution over a decade of work on human evolution, with circumstantial and solid evidence from archaeology, paleontology, anthropology, biochemistry, nutrition science and more. Now they connect more of the dots of evidence to their core hypothesis.

The core hypothesis begins about 2 million years ago, when the Homo genus demonstrably took a carnivorous turn. Yet arising as we did from herbivores, there was only so much energy we can obtain from lean meat – which would have applied to them too: about 50 percent to 35 percent of their daily calorie intake can come from protein, but eat more than that, and one will get a nasty case of nitrogen poisoning.

But they had no similar constraint regarding fat, a magnificent source of calories. They could eat as much of that as they wanted.

Who has fat? Big animals. A big animal was the total package for a hominin band: slow-moving with no tendency to escape, meat, nutritious marrow in their long bones, bones they could utilize to make tools, and great slabs of fat. Big animals have a lot of fat tissue proportional to their muscle mass. Small animals have little fat tissue. Whale blubber is famous and craved, rat fat not so much.

Our ancestors ate of these fat factories. A straight tusked elephants (extinct) Credit: Apotea

Put otherwise: The energetic return for a band of hominins from obtaining a giant plump animal (scavenged or hunted, which would last the tribe for weeks) was greater than the calorie gain from the same body weight of small lean animals.

So humans and our ancestors had an incentive to hunt the biggest animals they could, which were the fattest and would be the best return on their hunting and/or scavenging investment. In yet more separate work, Ben-Dor and Barkai have demonstrated that a million years ago, our ancestors may have embraced fire – a terrifying element to the uninitiated – less to cook, and more in order to smoke and preserve meat from giant carcasses, so the kill would last the tribe longer.

Note that huge animals reproduce more slowly than small ones. Our ancestors aren't the only reasons animals went extinct in this timeline, but the correlation between Homo arrival in a landscape and megafaunal extinction is striking.

Rats, not fat and not extinct Credit: Gallinago_media

And then there were none

Now we move onto the last 50,000 years. The megafauna were not entirely extinguished but they were severely diminished, especially in the Levant and Europe. All other human species that had clung on so far did go completely extinct, which Barkai and Ben-Dor also tie into their new hypothesis.

Only Homo sapiens remained. But how did we do so, and thrive?

To obtain smaller animals, we had to get smarter and develop better tools, which Barkai and Ben-Dor have also demonstrated in previous work. Our brains evolved and our toolkit did too. We had to have experienced profound cultural changes – most obviously in our weaponry and in the birth of art.

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