What is the origin of Homo sapiens?

The origin of Homo sapiens, or what is the same, our species, has always been a topic of interest to the scientific community, especially when they stopped believing in the idea of ​​divine creation and that all animals magically arose by generation spontaneous.

Two have been the main theories that have tried to explain how human beings are the way we are in At present, the theory that we come from Africa is the one that has the most strength and scientific evidence accomplished. Let's see what evidence has been found.

• Related article: "The theory of biological evolution"

The origin of Homo sapiens: what we know about the appearance of our species

Although today the idea that the first human beings must have arisen in some place of Africa and that, later, they were expanding by the world migrating, has not always had this idea. Throughout the study of the origin of Homo sapiensTwo main theories have been raised that have tried to elucidate what was the origin of our species.

The first is that of polygenism, also called the multiregional hypothesis, defending that modern human beings do not really come from a group of original humans, but from several groups of a previous species that were evolving by their own bill.

The second, which is the one most defended by current anthropology, is the one that defends that the first humans lived in Africa and, from there, they migrated to other parts of the world, thus spreading the species and adapting to the climates, emerging the races.

Polygenism

Polygenism is a theory about the origins of the human being that postulates the existence of different lineages that have resulted in the human races. The defenders of this theory said that, really, humans were a set of species, which were the result of different evolutionary processes that, coincidentally, coincided in some aspects.

The human races would be the result of the fact that the hominid link prior to what we now understand to be the Homo sapiens, would have split into different populations, which, over the millennia, would have given different species that could be classified as part of the same genus, not a species, which would be the humans. For this reason polygenism is also called multiregional hypothesis, saying that the current state of human beings is due to evolutions of different populations in various regions.

Those who defended these hypotheses used to be based on religious and pseudoscientific criteria, or taking empirical evidence in a very arbitrary way. Racism and slavery were justified based on these theses, since, if you have the notion that blacks, Asians and other races are, in addition to seeing themselves intellectually inferior to white, different from Europeans as a species, the use of individuals of these races as one who uses a mule or a horse to carry sacks would be equally legitimate.

African origin

But despite the fact that racism and slave positions defended the idea that blacks, whites, Asians and other races are the The result of lineages that had evolved separately and were, indeed, different species, these theses ended up being disregarded. side.

Today scientific evidence has shown that the origin of Homo sapiens it's in Africa, probably somewhere in the Rift Valley, although this has ended up being more and more in doubt.

What is accepted is that the current human species has to descend from a group of primal humans, the first Homo sapiens that had to spread throughout the world, changing their physical characteristics such as height, tone of skin, hair and eyes, teeth and particular shape of the skull but, which in essence, remain the same species.

Evidence in the paleoanthropological record, along with archaeological remains, historical inferences, and genetic evidence have indicated that the origin of Homo sapiens would date back to about 140,000 to 200,000 years ago in Sub-Saharan Africa. This is evidence accepted, practically, by the entire scientific community.

History and proofs of the theory

The African origin theory of Homo sapiens dates back to the end of the 19th century, with the figure of James Prichard, an ethnologist who argued that there were sufficient reasons to consider that human beings descended from the Black Africans, statements that, given the racist society of their time, needless to say were controversial. To assert that whites, who were seen as pure, intellectually superior, and the pinnacle of animal evolution were, in fact, descendants of blacks was tremendously controversial.

Charles Darwin, with his studies on the evolutionary variety in the Galapagos Islands, had already assumed that, by necessity, there had to be a common ancestor for all human beings. The first ancestor must have been, surely, some primate similar to a hominid, which Darwin's opinion should live in Africa, since on that continent it was the habitat of great apes, with a size and shape very similar to that of humans, in addition to the fact that some were able to stay in a bipedal position.

With the passage of the 20th century and thanks to the improvement of anthropological and genetic techniques, it was possible to establish with greater certainty where and when the origin of our species was.

Fossil evidence

From bones found in different places in Africa, it has been hypothesized that human beings anatomically Modernists evolved on that continent over the last 200,000 years, from a pre-existing population of hominids.

Anatomically modern refers to hominids that had traits very similar to those of modern humans: highly rounded skull, light and slender skeleton, facial retraction, graceful cheekbones ...

The first fossils with these characteristics were found in East Africa, near the Omo River (Ethiopia), being dated 195,000. These remains are called the Kibish men, and are considered the Homo sapiens older.

• You may be interested: "Lucy the Australopithecus: this was the fossil that changed everything"

Behavior and culture

Although it is logical to think that it is very difficult to know how hominid populations that lived long ago behaved, it It is true that they have left some remains behind that allow us to know, in a more or less suggested way, what their cultures.

Modern human behavior gave rise to the Upper Paleolithic, a period that was established in Europe 30,000 years ago, but in Africa it occurred earlier, about 70,000 years ago.

This is known from some paintings found in caves, as is the case in South Africa. They are abstract representations painted with red ocher. Objects, such as stone tips and arrows made of bone, have also been found between 70,000 and 90,000 years old.

Paleolinguistic studies

Paleolinguistics is the discipline that studies ancestral languages, that is, languages ​​that were spoken millennia ago, of which it is only possible to make assumptions on the basis of the living languages ​​spoken today, such as Indo-European reconstructed from European languages ​​and India.

But before Indo-European, and any other language, Protosapiens, the original language, must have been spoken before it was split as in the legend of the Tower of Babel.

Paleolinguists have hypothesized that languages ​​present more phonemes the more they are related to the oldest populated regions. That is, populations derived from a founding population, but which have been distancing themselves from it, gradually reduce their phonetic repertoire, having fewer sounds.

Do not fall into the error that these languages, having fewer sounds, will necessarily have less vocabulary. Phonemes and vocabulary are not directly correlated, but phonemes and distance from the African continent.

504 living languages ​​of the world have been studied, and it has been seen that those that have the most sounds, some having the rare "clicks" or Consonant clicks (ʘ, ǀ, ǃ, ǂ and ǁ), are found in Africa, as is the case of the Khoisan languages ​​with more than 140 sounds.

By cons, the languages ​​with the smallest phonetic repertoire are found in South America and the islands of Oceania, one of the regions that were surely populated by humans very late. Hawaiian, with only 13 phonemes, is the language with the fewest sounds.

Genetic evidence: Adam and Eve

Thanks to the study of human genetics, it is known that studying the family tree of the entire human species, there would have been an ancestor common male and one female, who have been called Mr. Adán, with the last name Chromosomal, and Mrs. Eva, with the last name Mitochondrial. The name is not accidental, since, in reality, the entire human species would descend from these individuals, comparable to the Christian idea of ​​Adam and Eve in the Garden of Eden.

The difference between biblical characters and these common human ancestors is that the latter did not know each other, since they lived in very different times. Mitochondrial Eve must have lived 190,000 years ago, surely somewhere in Tanzania, while chromosomal Adam is not very clear, but could have lived between 270,000 and 60,000 years ago.

Mitochondrial DNA, that is, DNA in a circular shape, very similar to that of a bacterium, which is found within the mitochondria, is inherited through the mother. The most recent common ancestor that this mitochondrial DNA would have given us had to be female, and that is why the existence of Mrs. Eva mitochondrial has been raised.

The Y chromosome can only be inherited by the male, and it is the sex chromosome that defines being male. Broadly speaking, it would have happened as in the case of mitochondrial Eve. All males would have a common ancestor, a male who had the first Y chromosome, which would be Mr. Chromosomal Adam.

The problem of laying the line

Many people, when they hear about human evolution, imagine the classic image of various individuals, arranged in a line, ranging from a quadruped monkey, through hominids of more to less hairy and arriving at Homo sapiens, with a spear and loincloth. This image, which although it is quite illustrative, leads to the erroneous belief that human evolution has occurred in a similar way to how Pokémon do. Phase 1: monkey, phase 2: australopithecus, phase 3: Homo habilis … final phase: Homo sapiens.

But actually the process was much more progressive, and this is observed in the skeletal remains. It is not easy to delineate where a species begins and ends by looking at its fossil record. It is clear that if you take two individuals who lived in chronologically widely separated times, such as Australopithecus and Neanderthals, differences are seen.

However, this is not so straightforward when comparing bones separated by barely 100,000 years or even from species that came to live together and that they had not yet become too differentiated, as must have been the case of the first Neanderthals and the first Homo sapiens. In fact, it is believed that a significant of the European population are descendants of fertile hybrids of Homo sapiens with Neanderthals, the latter species being responsible for the fact that Europeans suffer more cases of Crohn's disease, type II diabetes and biliary cirrhosis.

An example of this we have bone findings made in Jebel Irhoud, in Morocco. In the 1960s, bones belonging to two adult individuals and one child were found: two adult skulls, a child jaw, a child humerus, and a coccyx fragment. Since these bones had primitive or rather rough features, they were classified as Neanderthals.

Decades later, and re-analyzing the bones, he changed his mind. Those bones must belong to Homo sapiensWhat happened is that they had to be of a very primitive variety. This case shows how difficult it is to establish the line, since, since evolution is a process continuous, it is difficult to establish the criterion that serves to clearly delimit between a species and other.

Bibliographic references:

• Hublin et al. (2017). New fossils from Jebel Irhoud, Morocco, and the pan-African origin of Homo sapiens, Nature. DOI 10.1038 / nature22336
• Ritcher et al. (2017). The age of the hominin fossils from Jebel Irhoud, Morocco, and the origins of the Middle Stone Age, Nature. DOI 10.1038 / nature22335