The original population of America, that is to say, the date and pathway of the first human occupants of the American continents, is still perhaps one of the most highly debated topics in archaeology today. The main disputes are: the pathway(s) into the Americas, and the timing and number of the migrations of people that arrived in both continents prior to the arrival of the Europeans.
Pathways into America: Four Theories
There are no less than four major routes that scholars have seriously put forth over the past hundred years or so; each has its proponents and detractors.
- Preclovis and the Pacific Coast Migration
- Clovis and the Ice Free Corridor
- Solutrean Precursors to Clovis
- Trans-Pacific Contacts
One paper published by Perego et al. in January of 2009 suggested that Native Americans arrived in several waves into the Americas using two of these entry ways: the Ice Free Corridor and migration along the Pacific Coast. The Ice Free Corridor, however, may not have been opened at the time of the first colonization.
Timing of the Arrival(s)
The theory with the most proponents these days is that humans first arrived from the now-sunken landmass known as Beringia (or the Bering Land Bridge) and moved down into the continents along the coastlines, (Pacific Coast Migration). That theory became more likely as the evidence for people in the Americas earlier than the traditionally accepted first colonists called Clovis hunters has become more widely accepted. This earliest culture in the Americas is known as pre-Clovis. Although so far little is known about when pre-Clovis people arrived in the Americas, it is clear that they practiced a hunting-fishing-gathering lifestyle, different from Clovis.
One reason there is still so much unsettled discussion has in part to do with the timing and character of the Last Glacial Maximum (LGM). During the LGM, the most likely routes into North America were blocked by glacial ice between at least 18,000 and 24,000 calendar years ago (cal BP), and perhaps as long ago as 30,000 cal BP, and yet there are a handful of archaeological sites that appear to have dates older than 18,000.
Genetics and the New World Entrada
Continuing scholarly research has also attempted to understand the genetic, archaeological and linguistic diversity and similarities of Native American populations. These days, very few scholars support the notion that a single migratory wave from Asia populated America: it is clear from linguistic data alone that only multiple migration waves could explain the variety of languages used by Native North and South American populations.
DNA and linguistic analyses have been brought to the discussion, but neither yet provides an unequivocal answer. A paper by Perego et al. (2010) reported evidence for at least 15 maternal founding lineages, and hints that there may have been quite a few more.
A recent comprehensive study published in Nature in July 2012 (Reich et al.) assembled DNA data from 52 Native American and 17 Siberian groups, and identified at least three streams of Asian gene flow. Reich et al. confirm that the majority of Native American populations did originate from the first push, a fairly homogenous group that left Beringia more than 15,000 years ago. Two later migrations of people still are mostly from the first group. One migration result is that speakers of Eskimo-Aleut languages share about half their ancestry from a second migration, and Chipewyan Na-Dene speakers from Canadz share about 1/10th of their ancestry from a third Siberian stream.
The homogeneity of that first push supports the theory that Beringia was isolated from Siberia and the Americas by glaciers during OIS2, between 25,000 and 18,500 cal BP, although that remains to be seen.
Important Sites of the Colonization of America
Gonzalez, S. 2007 Archaeological Records: Global Expansion 300,000-8000 years ago, Americas. pp. 129-135 in Encyclopedia of Quaternary Science, ed. Scott A. Elias. Elsevier: London. Just found this good summary of the issues.
Perego, Ugo A., et al. 2009 Distinctive Paleo-Indian Migration Routes from Beringia Marked by Two Rare mtDNA Haplogroups. Current Biology 191-8.
Perego UA, Angerhofer N, Pala M, Olivieri A, Lancioni H, Kashani BH, Carossa V, Ekins JE, Gómez-Carballa A, Huber G et al. 2010. The initial peopling of the Americas: A growing number of founding mitochondrial genomes from Beringia. Genome Research (advance publication, currently free to download)
Reich D, Patterson N, Campbell D, Tandon A, Mazieres S, Ray N, Parra MV, Rojas W, Duque C, Mesa N et al. 2012. Reconstructing Native American population history. Nature in press.
A Preclovis vs Clovis bibliography has been built for this project.