Scientists from Atapuerca Revolutionizing Human Evolution

Once again, the findings of the now famous Pit of Bones, one of the most important sites in the Sierra de Atapuerca (Burgos, Spain), seems to "force us to revolutionize" human evolution as we have understood it so far.

Excavating at the Pit of Bones began systematically in 1984, but it was not until 1991 when the greatest accumulation of human fossils were found; an absolute scientific treasure older than 400,000 years from the Middle Pleistocene. Now, this impressive array of fossils has allowed scientists for the first time to very precisely describe the morphological characteristics of the individuals discovered. 

Over 1500 Fossils Analyzed

The study, which has involved a dozen experts from different institutions, has analyzed fossils from over 1,500 skeletons - from the neck down- of the more than 6,700 fossils uncovered from the Pit of Bones. They state that the fossils belong to at least 28 individuals of both sexes and various ages.

Skull number 5 of the Pit of Bones, as it appeared in the campaign of 1992. In later campaigns the jaw was exhumed. (Wikimedia Commons)

The remains of the individuals have been dated to around 430,000 years ago, with an average height of 1.63 meters and a body mass of about 69 kilos, which means that they were more heavily built than the later Neanderthals. Moreover, fossils have been recovered from a particularly heavy specimen who exceeded 90 kilos. However, his brain matter itself was said to be lower than the average Neanderthal.

"It is the first time we have described the postcranial skeleton of the largest display of fossils that exist in the history of paleontology," says Juan Luis Arsuaga, Director of the Center of Evolution and Human Behavior (Carlos III Health Institute - Complutense University) and first author of the paper presenting the research in the journal Proceedings  of the US National Academy of Sciences (PNAS), according to information published in the newspaper El País.

Ignacio Martinez, a professor of paleontology at the University of Alcala de Henares and co-author of PNAS explained that "The fact that humans of the Pit of Bones had smaller brains than Neanderthals means that that body size increased in parallel with and independently from the increase registered in the brain of the modern human species, which is considered a feature that is uniquely ours."

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Illustration of what a male from about 430,000 years ago may have looked like, the Pit of Bones, Atapuerca, Spain. (Photo: Kennis&Kennis / Madrid Scientific Films / El País)

"There has been a comprehensive investigation of the skeletons (body shape, weight, height, dimorphism in body size) and a detailed analysis of each anatomical part to establish the evolution of body shape in the genus Homo now proposed" Carlos Lorenzo, another of the coauthors of the study and researcher at the Catalan Institute of Human Paleontology and Social Evolution (IPHES), told the agency SINC .

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New Human Evolution and Neanderthal Revolution

The work and studies of the last 20 years on the fossils have led the scientific team to establish four major stages in the evolution of humans over more than four million years.

These four stages are Ardipithecus, from 4,000,000 years ago (arboreal and perhaps occasionally bipedal);  that of australopithecines like the famous "Lucy" from more than 3,000,000 years ago (primarily bipedal but with arboreal capabilities); that of the "archaic" humans who belong to the  Homo erectus  and the population of the Pit of Bones (tall body, wide and sturdy body frames and exclusively terrestrial locomotion), and finally that of modern humans (tall, thinner and more graceful skeleton.) "The four phases coexist in time but their order of appearance is sequential, one after another," says Arsuaga in his statement to “El Pais.”

Models of a Neanderthal man and woman. Neanderthal Museum, Dusseldorf. (Wikimedia Commons )

What is truly revolutionary in the information proposed by the team of researchers from Atapuerca is that it incorporates the Neanderthals in the third stage. Such inclusion would dismantle the model generally accepted by scientists until now. As explained by Juan Luis Arsuaga, what they propose would drop the classic concept “…in which Neanderthals are a product of a specific adaptation to the cold weather of Europe, while modern man, the current species, models the classic African Homo erectus. It is not like this. We believe that our species is the revolution. There are Neanderthals, with special adaptation, within the archaic model as well.”

Furthermore, "the great acceleration of encephalization, considered a distinctive feature of our species, as something unique, is not true" said Ignacio Martinez. The study’s results suggest instead that this process almost simultaneously and independently occurred in Neanderthals, as shown by the brain mass of their remote ancestors - the ancient beings from the Pit of Bones.

"Neanderthals were really smart; they were not super chimpanzees, as was thought for years. They talked and adorned themselves, now we also know that they had encephalization. In science it is very difficult to put forward a theory with just one case, you need to do comparative research, and our species is difficult to address if it is the only one of its kind. Now, with Neanderthals, we have a mirror species, another intelligent species that originated independently of ours, and this helps us to study ourselves," Martinez remarked to “El Pais.”

Members of the Atapuerca research team working on one of the sites. (Wikimedia Commons)

The controversy is undoubtedly present. We can expect months of paleontological debate since, under the new proposed scheme, the modern human would have originated in Africa at the same time as Neanderthals were adapted to live in the cold latitudes of the European continent ... And individuals from the Pit of Bones may show the first steps of an evolution that would suggest that Neanderthals were present far earlier than commonly believed.

Featured image: Comparison between the skull of a modern human (left) and a Neanderthal (right). Museum of Natural History in Cleveland. (Wikimedia Commons)

By Mariló T.A.

This article was first published in Spanish at www.ancient-origins.es and has been translated with permission.