From National Geographic
The human being is quite a case! At least everyone agrees on that. But what exactly distinguishes Homo sapiens from other animals, especially apes, and when and how did our ancestors acquire that certain something? In the last century countless theories have been proposed. And some reveal a lot, both about the times in which their proponents lived and about human evolution:
1. We manufacture tools:
"Toolmaking is a peculiarity of man," wrote anthropologist Kenneth Oakley in a 1944 article. He explained that apes use the objects they find, "but modeling sticks and stones for a specific use was the first recognized human activity”.
In the early 1960s, Louis Leakey attributed the start of toolmaking, and consequently the origin of humanity, to a species he called Homo habilis (Handy Man), which lived in East Africa about 2.8 million years ago. of years. However, as Jane Goodall and other researchers have shown, chimpanzees also modify branches for particular uses. For example, they pluck the leaves to "catch" insects hidden under the ground. Even crows, which lack hands, are quite skilled.
2. We are murderers:
According to the anthropologist Raymond Dart, our ancestors differed from the apes in that they were ruthless killers: carnivorous beings who "seized live prey with violence, beat them to death, butchered their battered bodies and dismembered them, limb by limb, satiating their voracious thirst with the hot blood of the victims, eagerly devouring the still throbbing flesh”.
It may sound like a tabloid reading to us now, but after the gruesome massacre of World War II, Dart's 1953 article detailing this "killer ape" theory struck a chord.
3. We share food:
In the 1960s, the killer ape gave way to the hippie ape. Anthropologist Glynn Isaac unearthed evidence of animal carcasses that were deliberately moved from the site where they died to places where an entire commune allegedly shared the meat.
In Isaac's view, sharing food led to the need to share information about the location of food sources and consequently, the development of language and other distinctively human social behaviors.
4. We swim naked:
A little later, during the Age of Aquarius, television documentary maker Elaine Morgan claimed that humans are very different from other primates because our ancestors evolved in a very different environment: near water.
Losing body hair made us agile swimmers, while upright posture allowed us to walk in the water. The "aquatic ape" hypothesis was discarded by the entire scientific community. But in 2013, David Attenborough backed her up.
5. We throw things:
Archaeologist Reid Ferring believes that our predecessors began to humanize when they developed the ability to throw stones with great speed. At Dmanisi, a 1.8-year-old hominin site in the former Soviet republic of Georgia, Ferring found evidence that Homo erectus invented public stoning to scare off predators that haunted its prey.
"The Dmanisi individuals were small," explains Ferring. “The area was crawling with big cats. How were the hominins to survive? How did they get there from Africa? Part of the answer is that they threw rocks. ”He argues that stoning animals also contributed to socialization, because the success of the strategy required group effort.
6. We hunt:
In a 1968 article, anthropologists Sherwood Washburn and C. S. Lancaster argued that hunting did much more than inspire cooperation. "Our intellect, our interests and emotions, and our basic social life - in a very real sense, these are all an evolutionary consequence of our success in adapting to hunting."
For example, our largest brains developed as a result of the need to store more information about where and when to find prey. Likewise, the hunt allegedly led to the division of tasks by gender, leaving the task of searching for food to women. Which raises a question: Why do women also have big brains?
7. We trade food for sex:
Specifically, monogamous sex. According to the theory, published in 1981 by C. Owen Lovejoy, the critical turning point in human evolution was the rise of monogamy, about six million years ago. Until then, almost all sexuality was reserved for beastly alpha males who repelled rivals.
However, monogamous females favored males more able to provide food and willing to participate in raising children. According to Lovejoy, our ancestors began to walk upright because that allowed them to have their hands free and thus, they could return home with more food.
8. We consume food (cooked):
Large brains are voracious: gray matter requires 20 times more energy than muscle. According to some researchers, the brain would never have evolved on a vegetarian diet; On the contrary, our brains grew two or three million years ago, when we began to consume meat, a rich source of protein and fat.
And according to anthropologist Richard Wrangham, once our ancestors invented cooking "uniquely human behavior that facilitates the digestion of food", they wasted less energy chewing or pounding meat, so they had more energy available to their brains. In the long run, those brains developed enough to make the conscious decision to go vegetarian.
9. We consume carbohydrates (cooked):
Or maybe our bigger brains are due to carbohydrate loading, according to a recent article. After our predecessors invented cooking, tubers and other starchy plants offered excellent sources of brain nutrition, much easier to obtain than meat.
An enzyme in saliva called amylase breaks down carbohydrates into glucose required by the brain. Evolutionary geneticist Mark G. Thomas of University College, London points out that our DNA contains numerous copies of the amylase gene, suggesting that the enzyme - and the tubers - contributed to the explosive growth of the human brain.
10. We walk on two feet:
Did the turning point in human evolution occur when our ancestors came down from the trees and started walking upright? Proponents of the "savanna hypothesis" claim that climate change caused this adaptation. As Africa began to dry up, about three million years ago, the forests were reduced and the savannas began to dominate the landscape.
This favored primates that could stand up to look over the grass for predators, and those that could navigate effectively in clear terrain, where food and water were in secluded places. An impediment to this hypothesis arose in 2009 with the discovery of Ardipithecus ramidus, a hominin that lived 4.4 million years ago in present-day Ethiopia. At that time, the region was very humid and wooded; and yet "Ardi" could walk on two legs.
11. We adapt:
Richard Potts, director of the Smithsonian's Human Origins Program, suggests that many climate changes influenced human evolution, rather than just one trend.
He says that the emergence of the Homo lineage, nearly three million years ago, coincided with drastic fluctuations between humid and arid climates, and that natural selection favored primates that could cope with constant and unpredictable changes. Potts argues that adaptability is itself the defining characteristic of humans.
12. We unite and conquer:
Anthropologist Curtis Marean offers a vision of human origin that is well suited to our globalized age: we are the ultimate invasive species. After tens of thousands of years of living confined to a single continent, our ancestors colonized the planet. How did they achieve such a feat? According to Marean, the secret was the genetic predisposition to cooperate, an instinct that arose not from altruism but from conflict.
The cooperating groups of primates gained a competitive advantage over their rivals and thus their genes survived. "This unique propensity, coupled with the developed cognitive abilities of our ancestors, enabled them to skillfully adapt to new environments," Marean writes. "It also fostered innovation and spawned transformative technology - advanced projectiles that were used as weapons."
But what is wrong with all these theories?
Many of them are meritorious, but they have a common bias: the idea that humanity can be defined by a well-defined trait or group of traits, and that a single stage in evolution was the critical turning point in the inevitable path that led to Homo sapiens.
Our ancestors weren't beta testing. They weren't evolving into something, but merely surviving as Australopithecus or Homo erectus. And no single trait they had acquired was a turning point, because the result was never inevitable: the killer ape, toolmaker, stone thrower, meat and potato eater, cooperative, adaptable, and big-brained that we all are. And that continues to evolve.
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