It’s a curiosity in the animal world: we don’t stop growing for many years. Compared to individuals of other species, humans become adults late, around the age of 18, which, according to a study published in 2014, brings us closer to reptiles than to other mammals. Evidenced by our strong dependence on our parents or our wisdom teeth, which pierce the majority, when our primate cousins have long had full teeth.
Among the generally invoked culprits of this interminable youth, our main asset: this brain, so brilliant but greedy in energy, which leaves the rest of the body in tow. But another cause is clear today: the slow growth of small humans would give them time to master the complex search for food. A specificity which would, of course, be inherited from our distant ancestors.
Our varied diet in question
From the beginning, humans have practices that reflect their varied diet: they hunt, they fish, they gather. A new study published in Science Advances asserts that these multiple skills necessary for survival are slowly acquired during childhood.
To be convinced of this, researchers from the Max Planck Institute in Leipzig (Germany) and the University of Atlanta (United States) compiled the data collected from 714 children and adolescents from 28 contemporary gathering societies. They calculated that by the age of five, the average child has achieved only 20% of the productivity that will be his fifteen years later. The gain in this same productivity accelerates between five and ten years (30%), before doubling between 10 and 20 years.
But not all jobs are created equal. The anthropologist Ilaria Pretelli and his colleagues have distinguished four types of resources according to their difficulty of supply: on the one hand, fruits and marine animals, the collection of which requires less strength and individual knowledge; on the other, game and tubers, which require specialized tools, knowledge and strength. During childhood and until adolescence, the easy resources were privileged, while the most demanding then became predominant.
For the researchers, these results support the idea that, in humans, childhood has evolved “as an extended period” of learning to extract increasingly complex resources, characteristic of its varied diet.