A hand that evolved to be able to grasp the branches of the trees, also served us to hold an axe, a pen and the mobile or the computer mouse, while with one finger you slide the page to be able to read this text. The opposable thumb , larger brains and walking on two legs are the most characteristic elements when we talk about what differentiates us as a human species. But perhaps you have not heard so much the negative part of these attributes . In the long run we have benefited more than harmed, but the evolution of the human being is full of nuances with changes that were not always synonymous with advantage.
We do not come from the monkey
We are all apes (some more than others). According to the study of genetics, the separation of our branch, that of humans, began 13 million years ago, but the interbreeding could have continued until 7 million years ago. We are only a branch of the same evolutionary tree, therefore, in the same way that we consider ourselves mammals, it is not that we come from apes, but that we are apes.
Bipedalism: pros and cons
The appearance of bipedalism occurred long before the growth of our brain. Still earlier than Australopithecus , Ardipithecus ramidus is thought to have evolved primitive bipedalism 4.4 million years ago. Contrary to popular belief, bipedalism was not an adaptation to the open environments of the savannah. We know that the cradle of humanity is East Africa, but when we humans were still in the process of cooking, we lived in forest areas, in the trees, wow. It was the geological and climatic changes that made our original home a savannah.
But bipedalism gave us certain advantages : we could see above the tall grass; we had less body surface area exposed to the sun, which helps keep our backs from burning and keep us cooler in the African sun; and we could travel a greater distance using less energy.
The first biped par excellence, and hence its name, was Homo erectus : the first hominin to leave Africa and the species that managed to live for almost 2 million years. We sapiens have only been here a tenth and we are not accompanied by good predictions to match H. erectus.
But not all are advantages for the biped. Those who have suffered the most from this change in our way of walking have been women . Human childbirth was made more difficult and dangerous by walking upright. By walking on both lower limbs, the pelvic canal narrowed, making it difficult for a baby to come out, just as our heads began to grow. Unlike other mammals, human mothers and babies need help in childbirth. To compensate for the difficulty, we are born more prematurely, smaller and still to be formed. While it takes a kitten just weeks to forage on its own, we are helpless and dependent for years.
Size does matter
The first humans, 2.5 million years ago, had a brain of about 600 cubic centimeters. We currently have a brain mass averaging 1,200 to 1,400 cubic centimeters. What was it that drove the evolution of our huge brain? To be honest: we don’t know for sure.
It may seem that the bigger the brain, the better for the species, but the issue is more complex. In fact, Neanderthal brains were larger than ours. These big thinking machines make up 2 to 3 percent of our total weight, but consume 25 percent of our energy when we’re at rest. The price we paid was having to eat more and go without good muscles . Before we were stronger physically. You can’t have energy for a big brain and highly developed muscles at the same time. That is why we are able to win a debate with a gorilla, but it is not recommended to come to blows with him. Another thing is that the brain has compensated us to make a weapon with which to shoot down a gorilla, of course. But in the evolutionary timeline that was very recently, we’ve spent many more millennia on the run.
Hunters yes, but we were even more gatherers
We often imagine prehistoric human species with spears, traps, and strategies to hunt large prey like mammoths, giant bears, and bison larger than our current cows. But the reality is that we lived in constant fear of the great predators of the past and our subsistence consisted mainly of gathering plants, eating insects, hunting small animals and taking advantage of the carrion left by carnivores such as the jaguar or the cave lion.
For millions of years we were somewhere in the middle of the food chain. But about 400,000 years ago things began to change and, in the last 100,000, we definitely occupied the highest point in the chain. In an evolution, perhaps, too fast.
We go faster than natural
The evolutionary jump of Homo sapiens has been too great in such a short time. We have positioned ourselves as the dominant species on the entire planet without the planet having had time to adapt . The rest of the species that had their time of dominance needed millions of years and, with them, the world around them was also changing. In the words of Yuval Noah Harari:
“As lions became more deadly, gazelles evolved to run faster, hyenas to cooperate better, and rhinos to be more short-tempered.”
But the human being, being so defenseless on his own, has managed with his intellect and life in society to gain the dominant position despite his insecurities. Perhaps this is one of the consequences that has led us to have so many historical calamities.
References:
Dartnell, L. 2019. Origins. How the history of the earth determines the history of mankind. Debate
Harari, YN 2018. Sapiens. From animals to gods. Brief history of mankind. Discussion .
