The team from the Natural Environment Research Council and led by Dr. Silvia Gonzalez, analysed the DNA of skulls with markedly different morphologies to Native American Indians, commonly regarded as the first settlers of the Americas. The skulls are long and narrow, not in keeping with the Native Indians' broader, rounder features.

"They appear more similar to southern Asians, Australians and populations of the South Pacific Rim than they do to Northern Asians," said Dr Gonzalez of Liverpool John Moores University.

"DNA analysis of the Mexican remains suggest these people were at least partly contemporaneous to the first native American Indian settlers on the continent," she added.

"We think there were several migration waves into the Americas at different times by different human groups. The timing, route and point of origin of the first colonisation of the Americas remains a most contentious topic in human evolution."

This debate has been running for more than a century. Consensus is split between two camps: the first camp believe settlers came across the Bering Straits, from Russia to Alaska, at the end of the last ice age 12-15,000 years ago. Evidence for this theory comes from Clovis Points - huge tools used to hunt mammoths - found all over the American continent. DNA analysis of skeletal remains close to these Clovis Points suggest just four tribes are responsible for populating the continent. The second camp say colonisation happened much earlier than this, 20-30,000 years ago, but their techniques, using genetics, linguistics and dental morphology, have been steeped in controversy.

Dr. Gonzalez's team have evidence of a previously unknown group, the Pericues, who went extinct in the 18th Century. She suggests this tribe may not have taken the traditional route to the continent.

The work is one of 11 projects investigating whether environmental factors played a part in human evolution and dispersal. Funded by the Natural Environment Research Council, the programme is tackling major anthropological questions such as: how did we become the only true global species? Why did our ancestors swap the tropical beaches of Africa for the icy tundra? How do we explain our trademark big brains? What role did climate play in making us adapt quickly to different environments?

The programme, Environmental Factors in the Chronology of Human Evolution and Dispersal, is truly global in its outlook with scientists working in South America, Europe, Africa, the Middle East and southern Asia.

The editors, all professional anthropologists, selected papers representing many different research protocols and data sources in order to provide a multidisciplinary view of the issues. Contributors include evolutionary biologists, geneticist, behavioral ecologists, and historical linguists.

Kamille R. Schmitz, in her "Review of Bioarchaeological Thought," points out that "Genetic, skeletal, and dental morphological evidence overwhelming identify Asia as the homeland of the first Americans." Whether new evidence contradicts this finding, and how and when the Asians became Americans remains the subject o much theory and debate.

Carole A.S. Mandryk, in a paper entitled "Invented Traditions and the Ultimate American Origin Myth," debunks the long-standing consensus of an ice-free corridor that allowed early inhabitants of the New World to move south through the Canadian ice sheets. "This myth is still preferred by many individuals, despite the lack of supporting archaeological and geological evidence, partly because ideological and theoretical assumptions in academia and the popular press regarding the earliest Americans block consideration of alternative scenarios."

The papers in this volume are arranged in three parts responding to three areas of inquiry:

1. Who were the Pleistocene settlers of the American continents?
2. What route did they take?
3. What were the ecological effects of their colonization of the continents?

"It has no escaped the attention of its critics that much research on New World origins is heavily dominated by pattern searching and by a relatively mechanistic approach to interpretation that lacks any explicit conceptual framework to lend meaning to pattern," the editors point out. "The papers in this book are, perhaps, an initial step in redressing that deficiency."