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Blog científico

Publicado el 11 de marzo de 2015 por Eudald Carbonell

Ledi-Geraru (Ethiopia): the first of all humans

One of the issues that have always been in the background in the debate on human evolution has been what species of Homo was responsible for the manufacture of the first stone tools. The discovery in Olduvai of a skull of a hominid in the 60s of last century, which was named Homo habilis by well-known and already deceased anthropologists, Louis Leakey, Phillip Tobias and JV. Napier in Current Anthropology in 1965 opened the doors to the search for the first toolmakers in Africa.


For a long time a question hung in the air: who was responsible for the manufacture of the tools found at the Kada Gona site in the geological formation of Kada Hadar in Ethiopia? The oldest stone tools, with an age of 2.5 million years, were in this town and yet the oldest skeletal remains of hominids of the genus Homo ever found were more modern than the tools at about 2.3 millions of years of age. This led many archaeologists to think that other genera besides our own made tools.


At the beginning of this century we had the opportunity to analyse the lithic tools of Kada Gona that were published in 2000 in the Journal Archaeological Science, thanks to the help of our friend and archaeologist colleague Sileshi Semaw, at the Museum of Addis Ababa. We realised that taking into account this was the first proof of operational intelligence, those tools were already well developed and standardised, they were of medium and recurrent size, various raw materials had been used, etc. We thought there had to be a less elaborate lithic industry and of a chronology prior to what we were studying.


Indeed, the theory we maintain is that the Homo genus was responsible for the emergence of operational intelligence and, therefore, we should find skeletal remains of specimens as old as the industries themselves. This is exactly what just happened: the Science issue for this March publishes skeletal evidence, namely, remains of a skull and a jaw fragment of the Homo genus and fossil (LD.305-1). This supports our argument: we should probably find more industries older than 3 million years, since we already know that Homo is a very old genus, much older than we had known until now.


This is the first question that this exceptional discovery solves. Since cut marks have been found on bones of 4 million years of age at the same level as that of Australopithecus anamensis, this again raises the possibility of the existence of tools in this ancient chronology. In fact, only the handling of cutting lithic objects can produce marks that explain the intentional intervention on a corpse. These marks are very different from those left by fangs and teeth of predators. While the marks made with stone knives have a V-shaped cross-section, those by carnivores are U-shaped. As in 1964 in Olduvai, where the stone tools discovered had initially been associated to the famous Zinjanthropus boisei, discovered in 1959, the same could be happening now. Searches should be made for older fossils of the Homo genus to be able to verify that industrial activity, in the sense of the making of tools by a primate, probably emerged no later than 4 million years ago. The hominid jaw found at the Ledi-Geraru site in Hadar, with features of Australopithecus and Homo, opens the door to new research not only on the origin of our gender but on the possibility that the Homo genus is very old. This forces us to change the phylogenetic tree we all know.


This discovery, therefore, invites us to unblock a number of issues that were being proposed and always argued in small groups, but as there was no empirical evidence it did not reach a social scale. It has now already become a problem and we know we must continue investigating to fix it. In short, what are these issues? Is the Homo genus very old, much older than previously thought? Are there lithic industries older than 3 million years? Is the Homo genus the only one that made tools systematically or are there other genera that made them too? We know it has only been within the Homo genus where all species adapted thanks to operational intelligence, i.e., all species have socialised and evolved through technology. This, as we know, only occurs in the lineage of human primates. Is it possible that other genera have systematically used technology for adaptation? In my opinion, it is possible but unlikely. There are many questions, but the article about the discovery of the oldest Homo specimen on the planet that has just been published in Science has already had an impact on historical issues and nothing will be as before in the study of the evolution of early humans and their culture.

Eudald Carbonell Roura