Human Evolution: A Guide to Understanding Hominids
Who are we? Where are we from? Where are we going? Since ancient times, humanity has sought answers to these great questions, and one way of approaching their answers is the study of prehistory and our ancestors. Since Darwin’s theory of natural selection and the fact that species are not immutable has been widely accepted, many scholars and adventurers have striven to seek out our ancestors, in reconstructing the history of Homo sapiens, in finding that missing link’ or intermediate form from which our lineage separated from that of the apes.
Today we know that evolution is not a line, but has many ramifications, and that we are part of a large family, the hominids, which includes both orangutans, chimpanzees, gorillas and bonobos, and a lot of species already extinct. We are the only survivors of the genus Homo, but before us there were many others, and we even lived with some species like Homo neanderthalensis for thousands of years.
In addition, the history of our origins is so exciting that it is rewritten almost every day, because in many corners of the planet new deposits are being studied and knowing, with the latest techniques available, many more details about how our extinct relatives lived. Findings are continually produced and it is very easy to get lost with every new news or scientific study that is published.
David Benito’s book 'Historias de la Prehistoria' (Ed. The Sphere of Books) is an excellent guide for situating oneself in this era which, as the author indicates in the prologue, Even though it is the longest age in our history, it is the most unknown to the general public. Many times you have a biased image of that prehistoric man, brute, unhygienic and of limited intelligence, but you must not forget that without those people we would never have reached the development and comforts that we enjoy today., says Benito.
We have selected some of the facts and stories from the book to help the reader put his ideas in order. A simple guide that we can use to better locate each time a new news item about an archaeological find appears.
First of all, let’s get into the taxonomic plane. The genus Homo sapiens is part of the primate order, characterized among other things by having hands and feet with five fingers, opposable thumb- except that of our foot, which has lost that ability-, nails instead of claws, stereoscopic vision, and a larger cranial volume. Within the order of primates, we are located in the Hominoidea superfamily, which is divided into the family Hominidae (ours), and the family Pongidae, in which are orangutans, gorillas and chimpanzees.
Although the term "missing link" is now out of use, it reflects well man’s quest to find the first hominid, that common ancestor between humans and chimpanzees. We know that our lineage was separated between 5 and 7 million years ago and there are several applicants for the position of the oldest hominid. The most outstanding are Sahelanthropus tchadensis, Orrorin tugenensis and the genus Ardipithecus, which is the one that has the greatest acceptance in the scientific community.
For a long time the scientific community considered that the extinct genus Australopithecus could be the longed-for missing link. Today we know that, although they are related phylogenetically to humans, they are not the common ancestor, and that they go back in time almost twice as long as the time that separates humans and Australopithecus.
This genus has an antiquity range ranging from 4.2 to 2.5 million years and within it there are seven species described, although on some there is still no scientific consensus.
The most famous species is undoubtedly Australopithecus afarensis, and its star individual is Lucy, found in 1974 in the Afar desert in Ethiopia. The importance of this fossil lies in the fact that Lucy presented characteristics that made her very different from everything that had been excavated until then, and at that time it was the oldest known skeleton. Their discoverers, aware that they had found something important, celebrated it loud and clear, and say that the Beatles' song Lucy in the sky sounded repeatedly during the celebration. As has already been said, today we know that Lucy was not the missing link’, but it is surely the most well-known fossil remnant in the world, a sort of primitive star.
This name means "a" next to the man’: after the Australopithecus, there was a branch in two groups: the genus Homo and the genus Paranthropus, each with a specific ability to allow them to subsist in the environment in which they moved. This genus retains some features of Australopithecus such as reduced cranial capacity in relation to the size of the body and prognathism [ very protruding jaws-. One of the new features is the development of a very powerful chewing device that will allow them to take advantage of very hard plant resources.
This species is considered the first human, which emerged in Africa and presents the ability to manufacture its own tools (we speak of Mode 1 or Olduvai Sense technology) and, in addition, to plan them mentally, visualize them before processing. Its brain is larger than that of australopithecus, it has a less developed chewing apparatus and a more rounded cranial shape. The first fossils of this species were discovered by the Leakey marriage at the throat of Olduvai in Tanzania in 1962, although the report describing the findings was published two years later.
About two million years ago, the first great human expansion took place and Homo habilis left Africa. Currently, within H. erectus are considered fossil individuals found in Asia, while the specimens found in Africa that already have more evolved characteristics since H. habilis are framed in the species H. ergaster. With this species there is already talk of a new technology: Mode 2 or Achelense.
Photo: Flickr James St. John
This species, whose description has not been without controversy, refers to findings made in Dmanisi, Georgia. The archaeological remains represent an intermediate evolutionary stage between Homo erectus sensu lato and H. habilis. It has an age of 1.8 million years, a height of 1.5 meters and is attributed Olduvai Sense technology or Mode 1.
Recapitulating everything explained until then, it seems that from Homo habilis emerged new species with different geographical location: H. erectus in Asia, H. ergaster in Africa and H. antecessor and H. heidelbergensis in Europe.
The discovery of H. antecessor took place in the Atapuerca deposit in 1994 and represented a paradigm shift, although it was not, like all the great discoveries in this matter, free of controversy. Until that time it was thought that the first inhabitants of Europe had arrived about 500,000 years ago, but in Atapuerca signs were being found that the human occupation in this settlement was much older.
The species was described in an article published in the journal Science in 1997 and tells us of a surprising mixture of primitive and derivative characters. They were between 1.6 and 1.85 meters, weighed between 69 and 90 kilos and among the primitive features stands the dental apparatus, which would link them with African specimens. They are credited with Mode 1 technology.
We speak of the European lineage, and of a species that is very important for the understanding of human evolution, because it is the direct ancestor of the Neanderthal man.
There are fossils of H. heidelbergensis with dates between 600,000 and 400,000 years, such as Mauer’s jaw, and other more modern finds with chronologies between 400,000 and 200,000 years, among which are found several fossils found in the Sima de los Huesos (Atapuerca). They were humans with great physical corpulence and possessing a finer apparatus, although their communication would be quite different from what we have today.
Much has been said and written about Neanderthals, especially following the latest DNA studies which show that, at least in a timely manner, hybridization occurred between H. neanderthalensis and H. sapiens. Both species lived together for approximately 10,000 years on the European continent until the extinction of the Neanderthals, whose causes are still under discussion. Inbreeding, nutritional deficit or competition with the sapiens are some of the hypotheses discussed.
In any case, it seems that this classic vision that described Neanderthals as individuals more like beasts than humans is outdated. For more than 100,000 years they inhabited several continents of the planet and were able to adapt to very extreme conditions. With the Neanderthals the technological development also took an important step, and we talked about Mode 3 or Musterian.
Just as Homo neanderthalensis emerged in Europe from H. heidelbergensis, H. sapiens emerged on the African continent. Today we know that at least our species is almost 200,000 years old, as indicated by the finding of Louis Leakey in Omo, southern Ethiopia, in 1967.
The discovery of Homo floresiensis in 2003 broke with a scheme that had been a constant in all the findings related to human evolution: The process led to larger and larger individuals with greater cranial capacity. But the one also known as the Hobbit’ did not follow this pattern: a morphology more similar to the Australopitecus but a very recent chronology, which would put it at around 18,000 years old, and with its own surprisingly advanced technology.
Much has been discussed regarding the interpretation of these remains, and even many theories pointed out that it was not a species as such, but that its morphology was due to some pathology. However, there is a growing consensus that we would be facing an H. erectus that evolved and adapted to the conditions of the island, modifying its morphology by an effect of insularity.
Homo naledi is the last described species of the genus Homo, as the discovery took place in South Africa in 2013, and its discovery has broken many patterns. We are talking about a mixture of human characteristics with much more archaic ones, with a very human morphology but a reduced cranial capacity and closer to the Australopithecus. To top it all off, it seems that these individuals buried their dead, so they would have some sort of symbolic thought, a characteristic that had always been attributed to larger brain volumes.
We’re talking about the first hominid identified through the analysis of his genes, and his taxonomy is still under discussion. We know that this species, or subspecies, is still under discussion-, is related to both Homo sapiens and H. neanderthalensis, so its discovery, in 2008 in the cave of Denisova (Siberia), adds even more emotion to the panorama of prehistory.
Later, in 2019, the remains of a jaw found on the Tibet plateau were identified as belonging to this extinct species. The findings were published in the journal Nature and prove that Denisovans had spread beyond Siberia.
In addition, there is evidence that Denisova’s men hybridized both with us and with the Neanderthals: some people from Oceania, for example, have around 5% of Denisovan genes.
Photo: molar Denisova 4
In 2007, a team of scientists found human-looking remains on the island of Luzon in the Philippines. After many years of study, in 2019 the description of this finding was published: the remains would correspond to a new species of hominid, H. luzonensis, who lived on this island 67,000 years ago, and present an interesting mixture of primitive and modern features.
As with H. floresiensis, It is quite possible that the isolation caused by its insular habitat would have led H. luzonensis to evolve along a very different path from H. sapiens and the other hominid species with which it coexisted on our planet.
As we have seen, human evolution is fascinating, as are the stories of the most relevant discoveries we have about our origins. In a very enjoyable and easy-to-read way, David Benito manages to immerse us in this exciting world and feel in the shoes of the most famous paleoanthropologists when they came across these key findings that give us clues about the way of life of those who preceded us.
Historias de la Prehistoria’ is a reference work for every curious reader who asks about our origins.
