Ancient history

The four keys to human evolution

In his book From the monkey to the Man , the naturalist and writer Herbert Wendt said that "one of the greatest, most fascinating and perhaps disappointing discoveries that man has made is the elucidation of his own origin" , despite the fact that the field of research that studies it is one of the most recent, it did not appear scientifically until the 19th century. But our species goes back a long way, since it is the result of 3,500 million years of evolution that resulted in many others, most of them extinct. Therefore, the interest in determining what were the keys to the evolution of prehistoric man is obvious.

Here it is convenient to clarify concepts. Contrary to what is usually believed, the term prehistory it refers only to the stage prior to history and whose main characteristic is the absence of written documents. Therefore, it is a period that covers only the evolution of the first humans and their immediate ancestors; dinosaurs and others are left out, in the field of geology, paleontology, biology, etc. That doesn't take away an iota of interest; it only focuses on its specificity, forcing us to resort to the fossil record -with its limitations- and, for some time now, genetics.

The gastronomic revolution

Currently, humans are not exclusively carnivores but omnivores. That means that we incorporate meat into our original vegetarian diet at a given moment; a million years ago, approximately, by the hand of Homo erectus (The so-called hunter hypothesis says that this distinguished him from other hominids). This is a generalization, of course, since many animals that are initially only carnivorous can also take herbs (such as cats) and, conversely, many that feed on grass, fruit, leaves or grain can make exceptions if they find dry bones (case of camelids) or even hunt prey (such as chimpanzees).

The intake of meat was decisive for human evolutionary development, by providing a large increase in protein that determined the growth of the brain -by supplying it with more energy- and the improvement of speech. On the other hand, eating meat required less chewing time and, therefore, provided more freedom of movement, in addition to stimulating a smaller change in the size of the dentition and, consequently, of the general physiognomy:smaller teeth required less muscle , left more room for cranial capacity and lengthened the face. Likewise, this saving of time allowed the surplus to be used in the search for other complementary nutrients -fruit, berries...- that improved the diet.

However, raw meat is not easy to bite and digest either, which led to practicing the process of cutting it -stimulating the manufacture of stone tools- and roasting it -mastering the use of fire and killing in the process the germs and toxins that had-. In the fossil record there is a coincidence between the appearance of stone tools, the domestication of fire -not yet its deliberate creation- and the new carnivorous diet. Evolutionary biologist Faustino Cordón Bonet summed it up in the amusing title of a famous book he published on the subject in 1980: Cooking made man .

The taxonomic revolution

According to paleoanthropologists, the family Hominidae it underwent a split about 16 million years ago into two distinct evolutionary lines. One was the Ponginae , of which only orangutans remain today; 8 million years later the other, the Homininae , was in turn divided among the Gorillini tribes (gorillas and other extinct genera) and Hominini; the latter also underwent a two-way evolution, one of which gave rise to the genus Pan (chimpanzees) and the other to the genus Hom or (humans).

We therefore belong to the order of primates, descendants of small placental mammals that about 70 million years ago advanced towards the first prosimians. Competition from rodents prompted them to survive in the trees by adapting their anatomy to that environment. That process developed from the end of the Cretaceous, the Paleocene and the Eocene, when the two great continents, Laurasia and Gondwana, were moving apart.

40 million years ago, the anthropoids appeared, which in the Miocene diversified and colonized Africa, Eurasia and tropical America. Their flexible diet and resistance to cold - having a larger body that better conserves heat - led them to survive, while the prosimians disappeared. It occurred in a chronological segment between 25 and 5 million years ago, and it was when the aforementioned superfamily Hominoidea appeared. . But 3.5 million years ago, the climate changed and with it the whole landscape.

The Ice Age was over and the grasslands began to replace the forests, which produced a domino effect on the fauna, multiplying the large ruminants and causing some hominid primates to abandon the trees, free their hands and walk upright (thanks to the advancement of the foramen magnum , the insertion of the vertebral column in the skull), something very useful to spot prey or danger among the tall grasses of the savannah.

It was the genus Australopithecus , whose specimens lost some hair and acquired sweat glands (useful to withstand the heat of the savannah). They used the first instruments, although that honor is more appropriately awarded to a new inhabitant of the place, who brought the novelty of making them about 2 million years ago:Homo habilis . Like the australopithecines, this first man proper made tools, which favored hand-eye coordination (convenient for hunting) and built shelters.

But, in addition, he maintained closer social relations with his group and experienced a growth in cranial capacity that resulted in greater brain complexity, which laid the foundations for improved communication and learning. A million and a half years ago he passed the baton to Homo erectus , who still had more cubic centimeters of brain and a reduced pelvis to walk fully upright, in addition to making another crucial contribution:the mastery of fire, 500,000 years ago.

The cognitive revolution

It can be considered the first emigrant, since some groups left Africa to settle in Asia and Europe, originating several subspecies. Some were isolated and became extinct; others ended up constituting new species such as Homo antecessor , Homo ergaster and Homo heidelbergensis , to name the best known. They were the ancestors of Homo neanderthalensis , which adapted very well to a frozen Europe 300,000 years ago and lived until relatively recently, about 30,000, becoming extinct for precisely two reasons:that cold-adaptive superspecialization became a burden when the climate warmed and it had to compete with another new species better prepared, Homo sapiens .

In reality, although this is counted linearly, erectus, Neanderthals and Sapiens lived together for a long time, which has led to the question of what would have happened if the first two had not become extinct. A multispecies humanity? What repercussions would that have not only in universal history but in religion, culture, politics...? Uchronías aside, and against the hypothesis of the extermination of the Neanderthals by a more intelligent species (which, therefore, would have better weapons, strategic ability and adaptation to the environment), genetics has shown the existence of a small percentage of their genes in our DNA, so there was some miscegenation.

The Neanderthals, we said, had to face a climate different from that of Africa, colder, which constituted an evolutionary stimulus. Of course, this always originates from successful mutations (during DNA sequencing they are usually produced but, except in specific cases, those that are profitable tend to survive in the species) and in that case it was reflected in the aforementioned adaptation that in the end It took its toll but, in the meantime, it led to another increase in cubic centimeters of brains (more than sapiens, in fact), to the use of clothing to protect themselves and even to the first abstract thought.

Indeed, Neanderthal man was not only the first to manufacture a very characteristic stone industry -the Mousterian-, to inhabit caves and huts built with bones and skins in a stable way, and to organize himself socially in clans, but also to become aware of his own humanity, protecting the sick and wounded of the group, conceiving symbolic concepts, practicing the ritual burial of the dead and developing the first artistic manifestations. There is no consensus on whether he could speak like sapiens, but probably in a cruder way, which would imply a language.

The extinction of the Neanderthals about 39,000 years ago left the Earth in the hands of Sapiens. It was they who led the great cognitive revolution about 50,000 years ago; the one that illuminated the appearance of bows and arrows, oil lamps, art with capital letters and primitive navigation, which allowed reaching land beyond the seas like Australia. Stone tools were perfected, giving rise to various types, increasingly specialized, and fire was finally fully mastered, as well as spoken communication thanks to the confluence of the pharynx and larynx, which gave man an enormous advantage over animals. by favoring coordination and strategy.

The agricultural revolution

As we have seen, the climate had softened since the last cold wave that closed the Pleistocene, the one during which man passed from Asia to America through the so-called Beringia Bridge (a land corridor in the Bering Strait) in a long time span between 70,000 and 12,000 years. The northern ice began to melt about 15,000 years ago, causing a rise in sea level and new lands to emerge, some authentic orchards such as the Sahara, while low temperatures retreated to northern and mountain areas.

That meant two things. The first, the physical adaptations to the different climate of each region, which gave rise to the different phenotypes within the same species:dark skin protected against excessive exposure to ultraviolet radiation from the tropical sun, while pale skin favored the opposite. in cloudy places (something necessary to synthesize vitamin D); Likewise, a tall and thin body was ideal to keep cool in extreme heat, compared to a stocky and stocky one, better to retain that heat in a cold environment.

The second thing he supposed was that the new climatic conditions and intellectual development brought about a revolution that, for some authors, was perhaps the most important that human beings have experienced:agriculture. It happened about 13,000 or 10,000 years ago, in the middle of the Neolithic, and by multigenesis, in several places simultaneously, often around large rivers (Tigris, Euphrates, Nile, Indus, Yellow...). The pioneers were Mesoamerica, where corn, beans, pumpkins and cotton were grown; the Fertile Crescent, where wheat, barley, peas, and lentils were farmed; and the Chinese southeast, with millet, rice, broad beans and yams; then followed South America, India, the Sahel...

This meant an increase in population because a cultivated land allowed to feed more and better than the hunter-gatherer activity, not depending on chance or the whims of Nature. And if the collection of food had led to agriculture, hunting did so in the domestication of animals, giving rise to livestock. Combined both, there was a new situation that inevitably led to a sedentary lifestyle, with all that this implied:technical improvement of tools, architecture, ceramics, crafts, commerce, job specialization, urban planning...

Also laws, religious cults and social stratification. Civilization, in short, that in order to manage itself gave birth to a fabulous invention:writing. With it, prehistory and the hominization process ended to give way to history and humanization.