Ancient Mexico, Brazil, DNA, Luzia

Tests on skulls found in Mexico suggest they are almost 13,000 years old - and shed fresh light on how humans colonised the Americas. The human skulls are the oldest tested so far from the continent, and their shape is set to inflame further a controversy over native American burial rights. Mexico appears to have been a crossroads for people spreading across the Americas.

The skulls were analysed by a scientist from John Moores University in Liverpool, UK, with help from teams in Oxford and Mexico itself. They came from a collection of 27 skeletons of early humans kept at the National Museum of Anthropology in Mexico City.

These were originally discovered more than 100 years ago in the area surrounding the city. The latest radiocarbon dating techniques allow dating to be carried out on tiny quantities of bone, although the process is expensive. Dr Silvia Gonzalez, who dated the skulls, said:

"The museum knew that the remains were of significant historical value but they hadn't been scientifically dated." "I decided to analyse small bone samples from five skeletons using the latest carbon-dating techniques," she told BBC News Online. "I think everybody was amazed at how old they were." The earliest human remains tested prior to this had been dated at approximately 12,000 years ago. Domestic tools dated at 14,500 years have been found in Chile - but with no associated human remains. The latest dating is not only confirmation that humans were present in the Americas much earlier than 12,000 years ago, but also that they were not related to early native Americans.

The two oldest skulls were "dolichocephalic" - that is, long and narrow-headed. Other, more recent skulls were a different shape - short and broad, like those from native American remains. This suggests that humans dispersed within Mexico in two distinct waves, and that a race of long and narrow-headed humans may have lived in North America prior to the American Indians. Traditionally, American Indians were thought to have been the first to arrive on the continent, crossing from Asia on a land bridge.

Dr Gonzalez told BBC News Online: "We believe that the older race may have come from what is now Japan, via the Pacific islands and perhaps the California coast. "Our next project is to examine remains found in the Baha peninsula of California, and look at their DNA to see if they are related.

Sites with triangular and sometimes stemmed points and diverse modern fauna and flora, date to between 11,500 and 8,500 years ago. The first secure evidence of early Paleo-indians on the Pacific coast was from two south Peruvian sites with beginning dates between 11,100 and 10,700 years ago. At the sites Quebrada and Jaguay, the ancient hearths contained carbonized fragments of stone tools and remains of shellfish, small fish, and birds, but no large game.

Luzia: Several studies concerning the extra-continental morphological affinities of Paleo-Indian skeletons, carried out independently in South and North America, have indicated that the Americas were first occupied by non-Mongoloids that made their way to the New World through the Bering Strait in ancient times. The first South Americans show a clear resemblance to modern South Pacific and African populations. In none of these analyses the first Americans show any resemblance to either northeast Asians or modern native Americans.

So far, these studies have included affirmed and putative early skeletons thought to date between 8,000 and 10,000 years B.P.

In this work the extra-continental morphological affinities of a Paleo-Indian skeleton well dated between 11,000 and 11,500 years B.P. (Lapa Vermelha IV Hominid 1,"Luzia") is investigated, using as comparative samples Howells' (1989) world-wide modern series and Habgood's (1985) Old World Late. The results obtained clearly confirm the idea that the Americas were first colonized by a generalized Homo sapiens population which inhabited East Asia in the Late Pleistocene, before the definition of the classic Mongoloid morphology.

Above: A skull belonging to a roughly 20 year old Australoid woman that was unearthed in Brazil by the French archaeologist Annette Amperaire in 1971, nicknamed “Luzia”. Since Luzia's discovery, at least 50 similarly un-mongoloid Palaeoamerican remains have been found in the Lagoa Santa area near where    "Luzia" herself was found. They all seem to have been buried within a small area that may have been a cemetery. This raises the intriguing question of whether the Lagoa Santa population at this early time, was perhaps already settled in a specific area and perhaps were even no longer just hunter-gatherers.

Deep inside an underwater cave in Mexico, archaeologists may have discovered the oldest human skeleton ever found in the Americas. Dubbed Eva de Naharon, or Eve of Naharon, the female skeleton has been dated at 13,600 years old. If that age is accurate, the skeleton—along with three others found in underwater caves along the Caribbean coast of the Yucatán Peninsula.

DNA: Dr Gonzalez,  John Moores University Liverpool, Archaeologist Annette Amperaire