From the onset of human evolution, we have shared the planet with megafauna. Most have gone extinct. Though megafauna – loosely defined as large animals weighing from around 40 kilograms (nearly 90 pounds) to tons – began to decline about three million years ago, there was a marked extinction event in the late Quaternary, from about 132,000 years ago to modern times.
What happened to all these species, from the elephantids of the north to the giant sloth of South America, from the cave lions of Eurasia to Megalania, the seven-meter-long giant lizard of Australia? Climate change and predation, to differing degrees in different places. Apparently, in a lot of cases we ate them.
While the fate of each is species-specific, a 2014 report showed strong ties between the severity of extinction and hominin spread.
Now, a new study by researchers at Tel Aviv University, setting aside the issue of why the megafauna declined, argues that their existence – and subsequent extinction – was critical to aspects of our evolution and behavior. The paper was published in the prestigious Journal of Anthropological Archaeology.
In the dimmest reaches of human evolution millions of years ago, the ape ancestral to ourselves was apparently a plant eater; likely augmented by the odd lizard or insect. Carnivory proper, complete with smashing bones to access the marrow, is thought to have entered the hominin diet at the stage of the australopithecines or Homo habilis, at least 2.6 million years ago, based mainly on fossil animal bones with butchery marks in Ethiopia and Kenya.
Certainly by the time of Homo erectus (which lived from 2 million to 300,000 years ago), meat and fat had become a major component of the diet, according to evidence from about 1.5 million years ago.
Based mainly on ethnographic data from recent hunter-gatherer groups in Africa, some researchers have argued that erectus and other hominins probably didn’t eat many megafauna, but subsisted to a large degree on foraging plants and hunting smaller prey. In their new paper, Miki Ben-Dor and Ran Barkai of Tel Aviv University argue that as long as megaherbivores had been around, hominins preferred them to other food sources. They also argue that drawing conclusions about the diet of our prehistoric forefathers from modern hunter-gatherer groups, as has been widely done, is misleading.
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Giant herbivores were critical to survival throughout human evolution until their decline and extinction (which accelerated in the last 40,000 years). Hominins only adapted to eating a relatively high plant component and hunting small animals when they had to, the researchers conclude.
The era of the giants
To be clear, megafauna still exist – from the Komodo dragon and crocodilians among the reptilia to the elephants of Africa and Asia, the big cats and bears still clinging on, and so on. Horses and hippos, and even the capybara, are also megafauna. Most of the still extant megafauna are under terrific stress, and it isn’t from climate. But many megafauna that thrived in the Quaternary were evidently unable to adjust to the warming at that era’s end.
A word on the names of the epochs. The Quaternary consists of two epochs: the first was the Pleistocene, from about 2.6 million years ago to 11,500 years ago; that second period from 11,500 years ago is called the Holocene, and is the period in which modern human civilization developed as indicated by agriculture, urbanism, writing, etc.
The Pleistocene was mostly cold, but at finer resolution it was characterized by swings between ice ages, which could last as long as 100,000 years, to warm intervals called interglacials, which averaged about 10,000 years. We are now in the Holocene interglacial.
Throughout most of the Pleistocene, living among megafauna was the rule. Only since the late Pleistocene have they become the exception.
Also, since the mid-Pleistocene, and possibly earlier, early humans were omnivorous but from the perspective of the environment, they apparently became “hyper-carnivores” – beating out the other major predators to get the giant herbivores.
As for the why, Ben-Dor and Barkai list four reasons, including that they provided a bigger bang for the buck. Catching a rabbit is a hassle for very little meat. But one effort to bring down an elephantid or a deer provides a feast. Crucially, the big animals had a relatively high fat content. Also, as Ben-Dor and Barkai put it, megafauna are characterized by “high biomass density.” Meaning?
“We are animals and need to eat for energy,” Ben-Dor explains to Haaretz. “Most of the potential energy in an environment is in megafauna, like elephants, because they constitute more than 50 percent of the biomass where they exist. So, if I’m an animal that eats herbivores, most of the potential energy lies in elephants. If I can hunt elephants, why mess with other things?”
Which leads to the how. We don’t know how megafauna were hunted over a million years ago, but Ben-Dor has ideas. “Elephants have to drink every day and they take certain paths to the waterhole. The hominins could have dug a pit, concealed it with vegetation and when an elephant fell inside, then they could kill it,” he postulates.
Asked if they would likely have bashed the struggling pachyderm to death with rocks, which sounds extraordinarily onerous, he suggests that even erectus had spear technology. “It wouldn’t take more than a sharpened wooden spear two or three meters in length,” he says. The wooden spears would hardly survive the eons for us to discover, and the earliest known spears were found at Schöningen, Germany, and dated to “just” 300,000 years ago. But it is “pretty clear” that erectus and its ilk had the mental ability to take a branch and fashion a spear, Ben-Dor says. “There are stone tools from the time of erectus with marks indicating that they served to process wood.”
Barkai agrees regarding the spears. In his opinion however, the most efficient method to kill an elephant would have been stalking, possibly with the help of camouflage, and spearing the elephant in the abdomen – literally, its soft underbelly – from close up.
Anyway, however they achieved it, erectus ate megafauna. Erectus sites have been found with butchered remains of all sorts of huge herbivores: elephants, rhinos, hippos and more.
The ‘Paleo diet’ and rabbit starvation
The so-called Paleo diet is a misnomer because it’s supposed to be based on how people ate when farming emerged – which was the Neolithic, not the Paleolithic. And it’s misleading because the Paleolithic peoples had neither a steady supply of trendy seeds or fruit, and didn’t aspire to eat lean meat, though Ben-Dor points out that the revamped "Paleo diet" acknowledges the importance of fat. There’s a reason we find roast fat irresistible. We need it.
In 1983, John Speth of the University of Michigan, Ann Arbor, examined a bison butchery site, observed that the prehistoric consumers seem to have focused on the fatty parts of their deceased meals and scorned the femur, Ben-Dor says. Speth subsequently formulated the “protein ceiling” theory: that there is a finite proportion of our energy needs we can get from protein, beyond which we might as well not be eating.
Ben-Dor explains: Fat is a compound of hydrogen and carbon. Sugar is a compound of hydrogen, carbon and oxygen. Protein has all that plus nitrogen. Our bodies can use sugar or fat to create energy “cleanly.” If we exploit protein for energy, our bodies have to vacate the nitrogen – but our ability to extract and excrete nitrogen is limited. If there’s too much, we get sick. Cats evolved to get 80 percent of their energy from protein, but we didn’t.
“Somewhere, there is a ceiling. Homo sapiens can get between 35 to 50 percent of our energy from protein; the rest should come from fat and carbs. If we eat too much lean meat, we suffer from protein poisoning,” Ben-Dor says.
Another name for protein poisoning is “rabbit starvation.” The name is derived from European fur hunters wintering in the forest, who would sometimes become dependent on rabbits for food. From a certain point, their bodies couldn’t derive energy from the low-fat meat and no matter how many lapins they ate, they couldn’t satisfy their hunger and would get sick to boot. (There is a theory that Neanderthals, to name one hominin species, evolved an enlarged liver “in order” to handle much higher levels of protein in their diet.)
Add to this mix the fact that megaherbivores are fattier than smaller mammals, and you have the reason why we would strain ourselves to catch the big ones. And when they were gone, we had to adapt in behavior and technology to acquire the same energy from smaller animals with less fat, at the same energetic cost.
“In the time frame between Homo erectus and the next in line, tools became smaller and [there was] adaptation to hunting small animals,” Ben-Dor explains.
For instance, we know that in Africa the bow and arrow were developed around 80,000 to 60,000 years ago. Projectile technology is dandy for nailing fleet-footed or winged prey.
Even earlier, at least 200,000 years ago, hominins were hafting stone points to the end of their spears. Hafted spears were used to hunt large game, Barkai says, and would have been suitable to hunt smaller animals too because megafauna still existed – but had begun to decline.
It seems the decline of megafauna in Africa actually began around three million years ago, so we weren’t responsible for that. But as the more advanced hominin lines arose, the decline accelerated.
In the Levant, elephants disappear from the fossil record around 400,000 years ago, which coincides with the appearance of a new stone tool technology called Levantine Acheulo-Yabrudian. In parallel, based on fossil teeth found at Qesem Cave in a layer dating to 400,000 to 200,000 years ago, erectus was supplanted by a new hominin. As the elephant went, it seems, so did erectus.
The archaeological record indicates that plants gained the ascendance in human diets about 40,000 years ago, as the big animals largely disappeared.
A last word on the example of modern hunter-gatherers to argue that hominins weren’t megafauna-centric. Studies based on surviving hunter-gatherers, the Hadza of Tanzania and Ju/’hoansi of Namibia, postulated that prehistoric hunter-gatherers would also have subsisted mainly on plants and augmented their diet with animals.
Ben-Dor and Barkai argue, though, that modern hunter-gatherers’ exploitation of big animals is underrepresented. Also, if the hunter-gatherers are subsisting mainly on plants, it is because the megafauna are depleted: Barkai adds that their hunting of the ones that remained had been constrained by the colonial powers.
Another reason comparison with modern hunter-gatherers is invalid is that today they have technology (mainly metal) to process and cook foodstuffs, which they didn’t have in the Paleolithic, Barkai points out: “So, ecologically and technologically, we can’t compare the diet of modern hunter-gatherers with the Paleolithic until the time the big animals disappeared.” And they are sorely missed.