Homo sapiens was not separated into races or different physical types before settling on all the continents, including the Americas, the last great land block conquered by the species, with the exception of the frozen Antarctica. The initial group of hunter-collectors who came here more than 15,000 years ago from Asia along a path today occupied by the Bering Strait had an anatomical structure that was very similar to that of the first population of modern humans who migrated from Africa, between 55,000-70,000 years ago. After leaving the cradle of humanity man entered Asia, which served first of all as a base for conquering two important points on the globe, Europe and Australia, and later a third, the Americas. “Until 10,000 years ago all Homo sapiens present on any continent had a standard African cranial morphology,” says bio-anthropologist Walter Neves, from the University of São Paulo (USP). “The raciation process had not yet begun.” The appearance of physical types, like the Caucasians and Mongoloids (Asians with almond-shaped eyes and a flat face), was a very recent biological phenomenon and occurred after man had spread over practically the whole of the Earth.
The researcher defends this controversial hypothesis in a scientific article published in the March edition of the American Journal of Physical Anthropology. In this work Neves and a further two physical anthropologists – Brazilian Mark Hubbe, who works at the Archaeological Investigation Institute and the Museum of the Catholic University of the North, Chile, and Greek Katerina Harvati, from the University of Tubingen, in Germany – compare 24 anatomical characteristics of the skulls of human beings who lived between 10,000 and 40,000 years ago in South America, Europe and East Asia, and of individuals from the present day from these three regions, in addition to people from Sub-Saharan Africa, Oceania and Polynesia. In all 48 ancient skeletons were compared (32 from South America, 2 from Asia and 14 from Europe) and 2,000 present-day ones. “Regardless of their geographical origin, members of the ancient populations are much more like their contemporaries from the past than they are humans of today,” comments Hubbe. In other words, the physical features of those who left Africa and 40,000 years later settled in the Americas were practically the same. According to this view, the conquest of the world was a rapid phenomenon (Homo sapiens used coastal routes that were less difficult to overcome), which gave man no time to adapt physically to his new environment.
The results of the study support the settlement model of our continent that has been defended for more than 20 years by Neves, whose work is largely funded by FAPESP. According to this hypothesis the Americas were colonized by two migratory waves of distinct peoples that crossed the Bering Strait at different times. The first comprised humans who, 15,000 years ago, still had this “pan-African” morphology, to use a term employed by the researcher from USP. Members of this initial band of hunter-collectors are likely to have looked like Luzia, the famous 11,000-year old female skull, found in the Minas Gerais region of Lagoa Santa. They had broad noses and wide eye sockets, a forward-projecting face and a narrow, elongated head. Although it is impossible to determine with any degree of certainty the color of their skin they were probably black. All their descendants disappeared mysteriously at some point in pre-historic times for unknown reasons and left no representatives among the tribes that are present on the continent today.
Humans with African features were always in accordance with the ideas of Neves, and they were largely replaced by individuals who came in a second migratory movement from Asia to the Americas. The new group entered the New World more recently, between 9,000 and 10,000 years ago and included only individuals with the physical characteristics of the so-called Mongoloid people, like current Orientals and the indigenous tribes found even today on our continent. Human beings with this more Asiatic appearance, which arose possibly as an adaptation to the extremely cold climate of Siberia and possibly of the Arctic, cannot have been part of the first migratory group to the Americas simply because this physical type had still not appeared on Earth – at least that is what Neves, Hubbe and Harvati say.
There is far from general consensus on this theory of the settlement of the Americas. DNA analyses taken from extinct and living indigenous populations of the continent, especially from the sequences contained in the mitochondrial genome (maternal line) and from the Y chromosome (inherited from the father), tell a different story. They favor the hypothesis that there was just one movement of individuals from Asia towards the New World and that this crossing occurred thousands of years before the date suggested by the archaeological evidence. “Practically all the biological diversity of current human types was already present in the single migratory group that entered the Americas,” says geneticist, Sandro Bonatto, from the Pontifical Catholic University of Rio Grande do Sul. “Only the Eskimos, a population that represents the most extreme and latest case of the so-called Mongoloid morphology, still had not originated and were not part of this group.”
In October 2008, Bonatto and colleagues from Brazil and Argentina published a scientific article in the American Journal of Physical Anthropology, the same journal that published Neves’ work. The study analyzed 10,000 pieces of genetic information and the anatomy of 576 skulls of extinct and current populations from North and South America. According to the article, approximately 18,000 years ago an already fairly physically heterogeneous group of hunter-collectors left Siberia and settled in Alaska. Forming part of this first band were people with Asian features and also with more African traits. The model is also different from the ideas of Neves and Hubbe because it also maintains that before entering the New World this group of colonizers made a forced stop in Beringia, the former piece of dry land that connected Asia to the Americas. Today under the sea, Beringia gave way to the Bering Strait.
The stop on the divide between the two continents occurred between 18,000 and 26,000 years ago, a period in which great glaciers were blocking entry to the Americas. When the route to the New World opened up the migration took place. However, the obligatory stop in Beringia, according to this hypothesis, produced specific mutations in the DNA of the population of migrants who were imprisoned on the frontier between two land masses. These genetic alterations are not found in the peoples of Asia, but were passed on to the descendants of the earliest Americans. A recent study, in which Brazilians took part, suggests that one of these mutations favors the accumulation of cholesterol in Indians from the continent (see text on “American inheritance“).
The two models described, which are not the only ones to deal with the question of how the Americas were settled, seem irreconcilable. But Argentinean physical anthropologist, Rolando González-José, from the National Patagonian Center in Puerto Madryn, who has already written scientific articles with Neves, Bonatto and other Brazilians, sees strengths and weaknesses in both approaches. “I agree that many variations present in the skull of man are of recent origin, but it also needs to be said that the ancient populations may have been fairly heterogeneous,” states González-José. “Neves’ model is not totally wrong, but it’s difficult to question the genetic data and it shows that all American Indians descend from a single population.”
There are other views on the settlement process of the Americas, some of them even more controversial. For archaeologist, Niède Guidon, the founder and president of the Museum of the American Man Foundation (Fumdham), who administers the Serra da Capivara National Park in Piauí, man was already in northeast Brazil 100,000 years ago. He came from Africa, by sailing from island to island and taking advantage of times when the sea was a lot lower than it is today. “Navigation is a lot older than is thought,” says Niède. “I don’t believe that Homo sapiens colonized the Americas via the Bering Strait.”
With almost 1,300 pre-historic sites, full of beautiful rock paintings, the park has already supplied 33 human skeletons and more than 700,000 stone artifacts for the institution’s collection. The dates disclosed by the archaeologist, which point to human presence in the northeast for at least 50,000 years, are questioned by many of her peers. Niède does not risk saying what the physical appearance of those responsible for the prehistoric drawings of the Serra da Capivara was like, although some preliminary studies suggest that they may have been similar to Luzia’s people.
The oldest site in the USA
A new and important piece in the complicated jigsaw that tries to reconstitute when Homo sapiens entered the Americas appeared at the end of March. A team of researchers, led by Michael Waters, from the University of Texas A&M, publicized their discovery of the oldest trace of human presence in North America. Located in Buttermilk Creek, Texas, the Debra L. Friedkin site houses some 15,500 artifacts made by man an estimated 15,500 years ago. These are basically blade-like objects, many of them unfinished and some two-sided, made from a type of quartz. “The site is in the center of the state and it must have taken man some time to find this location,” said Waters, in an interview with Pesquisa FAPESP. “It’s possible that he arrived in the Americas before then, but how much earlier, I couldn’t say. Only time and more hard work can tell us.”
The artifacts were dated using the luminescence technique. The method measures the energy from the last rays of the Sun (or from final exposure to intense heat) that was imprisoned in the sediment of the 20cm. thick geological layer, in which the pieces from the archeological site were found. No bones were found in the location, but scientists say that the objects were undoubtedly hewn by Homo sapiens and could have been used as knives or spearheads. They may even have formed part of an assortment of items that ancient humans carried with them in their wanderings.
The study was disclosed with much fanfare. After all, the ancient inhabitants of Buttermilk Creek lived 2,500 years before the so-called Clovis culture, which was defined from an archaeological site in New Mexico where 13,000-year old stone spear heads were found around 80 years ago. Until the 1980s, the idea predominated, and went largely unquestioned, that this culture was the oldest in the Americas. But the discovery over the last few decades of other sites that are as old or older than that of Clovis, both in North America as well as in Central and South America, has increasingly undermined this theory. The new findings in Texas seem to bury once and for all the aspirations that the ancient inhabitants of New Mexico were the first to settle on the continent. Since the blade-like objects from the Debra L. Friedkin site were found close to traces of Clovis-style spearheads and the two items bear similarities, the researchers believe that the second culture may derive from the first.
Origins and microevolution of man in America: a paleoanthropological approach III (nº 2004/01321-6); Type Thematic Research Grant; Coordinator Walter Neves – Institute of Biosciences of USP; Investment R$ 1,555,665.94 (Fapesp)
Hubbe, M. et al. Paleoamerican Morphology in the Context of European and East Asian Late Pleistocene Variation: Implication for Human Dispersion Into the New World. American Journal of Physical Anthropology. v. 50, n. 3, p. 442-53. Mar. 2011.