In anthropology and genetics, coastal migration is the theory that 100–200 thousand years ago, early human migrations first spread eastwards from a single origin in Africa to areas outside Africa, predominantly along coastal routes. Other terms, such as southern coastal route, rapid coastal settlement, coastal migration theory and Coastal Migration Model, are also used.
Coastal migration theory in Asia and Oceania
The coastal route theory is primarily used to describe the initial peopling of the Arabian peninsula, India, Southeast Asia, New Guinea, Australia, coastal China, and Japan. It is linked with the presence and dispersal of mtDNA haplogroup M and haplogroup N, as well as the specific distribution patterns of Y-DNA haplogroup C and haplogroup D, in these regions. The theory proposes that humans, likely similar to the Negritos or Proto-Australoids of modern times, arrived in the Arabian peninsula from Africa, then on the southern coastal regions of the Indian mainland, followed by spread to the Andaman Islands and modern-day Indonesia, and thence branching southwards to Australia and northwards towards Japan. National Geographic's Genographic Project uses the term 'Coastal Clan' to describe the initial human groups of Y-DNA haplogroup C who expanded eastwards out from Africa along the coastal route around 50 kybp.
Many centuries later, the ancestors of the Malagasy people are believed to have migrated coast-wise along the same route, but in the opposite direction (viz. westward along the shores of the Indian Ocean).
Coastal migration hypothesis in the New World
Sometimes, the theory is extended to cover onwards migration, via the Bering Strait (which was a land bridge during the last ice age), into North America, and then onwards to Central and South America along the western coast. Findings such as the report that the sediments in the Port Eliza caves on Vancouver Island, which indicated the possibility of survivable climate until 16 kybp in the area, have helped bolster the hypothesis recently. However, despite such research, the postulate is still subject to considerable debate. For the Pacific Northwest, Carlson, and others have argued for a coastal migration from Alaska pre-10,000 B.P. that predates the migration of Clovis people moving south through an ice-free corridor located near the continental divide. These people were followed by the Clovis culture, which some archaeologists believe moved south from Alaska through an ice-free corridor located between modern British Columbia and Alberta. Recent dating of Clovis and similar paleoindian sites in Alaska suggest that Clovis technology actually moved from the south into Alaska following the melting of the continental glaciers about 10,500 years ago.
As the ice sheets began to melt, it became possible for riverine-adapted people who made and used microblade technology to move west to the Northwest coast. A second migration of the Denali culture at around 10,700 b.p. brought peoples down the coast from Alaska. Carlson hypothesizes that a population with a maritime adaptation could have travelled south from Alaska down the coastal islands by watercraft, settling as the ice receded, then moving up rivers to the interior. This would account for early finds at Ground Hog Bay in SE Alaska and Namu, about 800 km south of Ground Hog Bay near modern Bella Coola dating to 10,180 +/− 800 b.p. and 9700 b.p., respectively. According to the Matson and Coupland dual migration hypothesis, Namu and Ground Hog Bay represent a second migration while the initial migration route south was through the ice free corridor. Part of the difficulty is the lack of site data prior to 10,000 b.p. as well as the limited number of archaeological investigations into the coastal migration model. Other factors affecting migration models are sea level changes and the question of available land mass to support migrating groups of people.
Evidence from Southeast Alaska and Haida Gwaii (Queen Charlotte Islands) in British Columbia, provides some data about food and land resources during the last glacial maximum. Fedje and Christensen (1999) have identified several sites on Haida Gwaii that date to post 9000 b.p. (642). The oldest human remains known from Alaska or Canada are from On Your Knees Cave, which is on Prince of Wales Island in Southeast Alaska. The individual, a young man in his early twenties when he died, has been dated to 10,300 years ago and isotopic analyses indicate the individual was raised on a diet primarily of marine foods. These data suggest that there are a number of submerged sites just beyond the shorelines of Haida Gwaii (Fedje & Christensen, 1999) and along the coast of Southeast Alaska. Paleoecological evidence suggests that travel along the coast would have been possible between 13,000 and 11,000 b.p. as the ice sheets began retreating. Between 13,000 and 10,500 b.p. Haida Gwaii had more than double its current land area (Fedje & Christensen, 1999:638). This area was flooded as the ice sheets began to melt between 11,000 and 9,000 b.p. (Ibid). Therefore any evidence of human occupation would now be below sea level. Conversely, older sites that are located near modern shorelines would have been approximately 24 km (15 mi) from the coast (Ibid). The antiquity of the lithic scatters that Fedje and Christensen (1999) have found in intertidal zones along the Haida Gwaii coast suggests an early human occupation of the area.
Fedje and Christensen (1999) support Carlson (1990), and Fladmark's (1975, 1979 & 1989) initial coastal migration model rather than the ice free corridor model proposed by Matson and Coupland (1995) through their investigations of intertidal zones on Haida Gwaii. The coastal region was quite hospitable by 13,000 b.p. to peoples with watercraft and a maritime adaptation. Furthermore, Fedje and Christensen (1999) argue that the coast was likely colonized before 13,000 b.p. (648). This assertion is based largely on watercraft evidence from Japan and Australia before 13000 b.p. If maritime peoples colonized Island Southeast Asia, Australia, western Melanesia, the Ryukyu Islands, and Japan between 50,000 and 35,000 years ago, they may well have been capable of migrating from Northeast Asia into the Americas as the North Pacific Coast warmed and deglaciated after about 16,000 years ago. Although no boats have been recovered from early Northwest Coast archaeological sites, this may be due to poor preservation of organic materials and the inundation of coastal areas mentioned above. We can still infer water travel based on the presence of artifacts made by humans found in island sites.
Other evidence comes from zooarchaeological finds along the Northwest coast. Goat remains as old as 12,000 b.p. have been found on Vancouver Island, British Columbia as well as bear remains dating to 12,500 b.p. in the Prince of Wales Archipelago, British Columbia. Even older remains of black and brown bear, caribou, sea birds, fish, and ringed seal have been dated from a number of caves in Southeast Alaska by paleontologist Timothy Heaton. This means that there were enough land and floral resources to support large land mammals and theoretically, humans. Further intertidal and underwater investigations may produce sites older than 11,000 b.p.. Coastal occupation prior to 13,000 b.p. would allow for people to migrate further south and account for the early South American sites.
Anecdotal evidence comes from the surviving Bella Bella oral tradition as recorded by Franz Boas in 1898. "In the beginning there was nothing but water and ice and a narrow strip of shoreline". Some believe this story describes the Northwest Coast during the last glacial maximum and that the story suggests that the Northwest Coast colonization occurred during the last ice age.
Further south, California's Channel Islands have produced even earlier evidence for seafaring by Paleoindian (or Paleocoastal) peoples. Santa Rosa and San Miguel islands, for instance, have produced five sites dating to the Terminal Pleistocene, including the Arlington Man site dated to ~11,000 radiocarbon years (13,000 cal BP) and Daisy Cave occupied about 10,700 radiocarbon years ago (~11,500 cal BP). Erlandson and his colleagues have also identified several early shell middens located near sources of chert, which was used to make stone tools. These quarry/workshop sites have been dated between about 10,800 and 10,500 RYBP (~12,000–11,500 cal BP) and contain crescents and finely made stemmed projectiles points probably used to hunt birds and sea mammals, respectively. Significantly, the Channel Islands have not been connected to the mainland coast during the Quaternary, so maritime peoples contemporary with the Clovis and Folsom complexes in the interior had to have seaworthy boats to colonize them. The Channel Islands have also produced the earliest fishhooks yet found in the Americas, bone bipoints (gorges) that date between about 10,000 and 9500 cal BP.
Even further south, the Monte Verde site in Chile has become accepted as a settlement around 14,800 years ago.
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- Phillip Endicott, Mait Metspalu and Toomas Kivisild (2007), The Evolution and History of Human Populations in South Asia: Inter-disciplinary Studies in Archaeology, Biological Anthropology, Linguistics and Genetics, Springer Netherlands, ISBN 978-1-4020-5561-4, "... The concept of a coastal migration was already envisioned in 1962 by the ..."
- Megan Bartlett (Spring 2006), Around the World in Four Millennia, Harvard Science Review, "... Scientists have followed their movements through DNA markers, culminating in what is known as the coastal migration model. ..."
- Renee Hetherington, Edward Wiebe, Andrew J. Weaver, Shannon L. Carto, Michael Eby, Roger MacLeod (2007), Climate, African and Beringian subaerial continental shelves, and migration of early peoples, Quaternary International, International Union for Quaternary Research, "... Alternatively, the coastal migration hypothesis suggests that people migrated along the southern edge of the exposed Beringian shelf and down the Pacific ..."
- Searching for traces of the Southern Dispersal, by Dr Marta Mirazón Lahr, et al.
- Metspalu et al 2006, Human Mitochondrial DNA and the Evolution of Homo sapiens.
- Vincent Macaulay, et al. (13 May 2005), "Single, Rapid Coastal Settlement of Asia Revealed by Analysis of Complete Mitochondrial Genomes; Vol. 308. no. 5724", Science Magazine 308 (5724): 1034–6, doi:10.1126/science.1109792, PMID 15890885, "... mitochondrial DNA variation in isolated "relict" populations in southeast Asia supports the view that there was only a single dispersal from Africa, most likely via a southern coastal route, through India and onward into southeast Asia and Australasia. There was an early offshoot, leading ultimately to the settlement of the Near East and Europe, but the main dispersal from India to Australia 65,000 years ago was rapid, most likely taking only a few thousand years. ..."
- Nina G. Jablonski (2002), The First Americans: The Pleistocene Colonization of the New World, University of California Press, ISBN 0940228505, "... Recent discoveries and events have breathed new life into the coastal migration theory, which suggests just the opposite of the ice-free corridor hypothesis—that maritime peoples first traveled around the North Pacific Coast then followed river valleys leading inland from the sea. Having a coastal route available, however, does not prove that such a maritime migration took place. Archaeological evidence for early boat use from islands along the western margin of the Pacific may support the idea that such a journey was technologically feasible, but archaeological data from the Pacific coast of North and South America are presently ambiguous about the origins of the earliest coastal occupants. ..."
- Kevin O. Pope and John E. Terrell (9 Oct 2007), "Environmental setting of human migrations in the circum-Pacific region", Journal of Biogeography 35 (1): 1–21, doi:10.1111/j.1365-2699.2007.01797.x, "... The expansion of modern humans out of Africa, following a coastal route into southern Asia, was initially thwarted by a series of large and abrupt environmental changes. A period of relatively stable climate and sea level from c. 45,000 yr bp to 40,000 yr bp supported a rapid coastal expansion of modern humans throughout much of Southeast Asia, enabling them to reach the coasts of northeast Russia and Japan by 38,000–37,000 yr bp ..."
- Spencer Wells (2002), The Journey of Man: A Genetic Odyssey, Princeton University Press, ISBN 069111532X, "... the population of south-east Asia prior to 6000 years ago was composed largely of groups of hunter-gatherers very similar to modern Negritos ... So, both the Y-chromosome and the mtDNA paint a clear picture of a coastal leap from Africa to south-east Asia, and onward to Australia ... DNA has given us a glimpse of the voyage, which almost certainly followed a coastal route va India ..."
- "The Genographic Project: Genetic Markers, Haplogroup D (M174)", National Geographic, 2008, "... Haplogroup D may have accompanied another group, the Coastal Clan (haplogroup C) on the first major wave of migration out of Africa around 50,000 years ago. Taking advantage of the plentiful seaside resources, these intrepid explorers followed the coastline of Africa through the southern Arabian Peninsula, India, Sri Lanka, and Southeast Asia. Alternatively, they may have made the trek at a later time, following in the footsteps of the Coastal Clan ..."
- http://www.rogerblench.info/Archaeology%20data/World/Manila%202006/Indian%20Ocean%20settlement%20paper%202006.pdf The Pleistocene settlement of the rim of the Indian Ocean
- Todd A. Surovell, Simulating Coastal Migration in New World Colonization; Volume 44, Number 4, August/October 2003, Current Anthropology, doi:10.1086/377651'
- Majid Al-Suwaidi (2006), A Multi-disciplinary Study of Port Eliza Cave Sediments and Their Implications for Human Coastal Migration, Library and Archives Canada (Bibliothèque et Archives Canada), ISBN 0494032995, "... A multi-disciplinary study at Port Eliza cave on Vancouver Island has refined the timing and character of late Wisconsinan environments and has significant implications for the human Coastal Migration Hypothesis ..."[dead link]
- Christy G. Turner (2003), "Three ounces of sea shells and one fish bone do not a coastal migration make", American antiquity (Society for American Archaeology) 68 (2): 391–395, doi:10.2307/3557086, JSTOR 3557086
- 1990 in Matson and Coupland, 1995:61-61
- Matson & Coupland, 1995:64
- Dixon 1999
- Dixon 1993, 1999; Matson & Coupland, 1995:64
- In Fedje & Christensen, 1999:648
- Erlandson 2001, 2002; Fedje & Christensen, 1999:648
- Boas, 1898:883 in Fedje & Christensen, 1999:635