The first large scale human migrations across continents
This essay will examine the question of the first large scale human migrations across continents, focusing on the colonisations of America and the Pacific region. In answering the question of when and how these continents were colonised, we need to be aware of what type of evidence are available to us, and how best to understand this evidence by employing a variety of analytical techniques.
Archaeological analysis differs from cultural anthropology: one cannot raise the dead and demand of them how and where they travelled. Rather, an archaeologist must be much like a detective, piecing together the available evidence to allow the past to speak more clearly. It is not so much a question of choosing which research methods to use as seeing which research methods will fit the available data the best. When utilising such evidence we must be aware of what we can say, and what we cannot say. For instance, if a settlement site gave a radiocarbon date of 32,000 years ago (kBP), this would also us to infer that there was settlement at this point: it would not allow us to demonstrate that there was not settlement previously to this date.
The archaeological and historical issues surrounding these colonisations are controversial. Part of the reason for this controversy is that the question of the initial colonisations is bound up in our considerations of what it is to be human. The colonisation of the Pacific is one of the first examples of anatomically modern humans utilising boats and sophisticated planning since the spread of homo sapien from Africa 100-200 kBP (Stringer & Andrews: 1998:1264). This essay will analyse the possible analytical methods that can be used on the evidence at hand, and demonstrate the extent to which one can validly talk about the colonisations, demonstrating the extent to which some of these debates have been mired in controversy that does not fit the data at hand.
II. The Evidence for the Colonisation of America
Humans leave various remains after them when they die. Some of the most useful of these are their bones, which we can use to understand diseases they might have suffered, wounds they might have incurred, and possibly, when all of this happened. One can also find the associated remains of humans: in the case of the colonisation of America we find one of the most useful, though controversial, sets of evidence are the bi-facial blades found at Clovis we shall discuss later. Often we can use the associations of a site to date the remains more accurately: for example by using the pollen cores we shall discuss later. This section will set out some of the available evidence in the colonisation of America we shall analyse, and remark on some of the lesser used methods of analysis, before concentrating on the use of radiocarbon and Accelerated Mass Spectrometry (AMS) in section IV.
II.I Dental Studies and Genetics
Until early in the 20C, there was very little idea about how America was initially colonised by anatomically modern humans. An initial task was to establish the closeness of the populations in the world, to get an idea of how homo sapien migrated around the world from Africa. One of the ways it is possible to trace the relations between populations is to analyse the dental record. Different populations evolve teeth in different ways. Turner (2002:136) has analysed various dental complexes around the world and found a remarkable degree of similarity between the dental complexes of north east Asia and the Americas. The analysis of the underlying structure of teeth is not without its risks, as the criticism of Turner’s work shows. Powell (1999) tries to show a Mongol origin for the people of America. However, his work is let down by both his statistical errors and by the fact he fails to account for the large degree of teeth ware that can mean a Sinodonty dental complex can be mistaken for a Sunadonty (Mongol) dental complex.
What makes Turner’s work so compelling is two-fold. The research he has done on dental complexes seems convincing. Moreover, it fits the other data that we have available. In terms of establishing closeness of populations (and thus likely paths of migration), genetic analysis can be useful. Fiedel (2000) uses mtDNA analysis to show the commonality of haplotypes between Asian and American population groups. MtDNA, the type studied by Fiedel, encodes only 37 genes rather than the 100,000+ of nuclear DNA, and by analysing the rate of mutation one can build up a calibration by checking them against a reference. In this task, mtDNA has two distinct advantages over nuclear DNA. First, all sequence changes are steady and neutral, akin to a fast ticking clock. This is important because we can only work out changes from looking at the genes that mutate the fastest. Unlike nuclear DNA, mtDNA is inherited through the mother alone, and thus all mtDNA must have a single female ancestor, enabling us to trace populations back to their common ancestor.
However, there are many problems with mtDNA analysis. Much of the work takes places in the control section of mtDNA, which is problematic because we do not know how to correct for multiple mutations. Furthermore, mtDNA is very unreliable over short periods, and these criticisms can extend to its use over a long period. Intervals of genetic stagnation may be interrupted by short burst of change, when a new mutagen enters the environment, or intense natural selection may affect all areas of the DNA. In such cases, it may no longer be the case that mtDNA mutations are neutral, putting the validity of the results of the tests in question. Furthermore (Wolpoff: 1992), there is evidence to suggest mtDNA strands play a role in several diseases, which undermines the claim that it is a neutral adaptation, and so the mutation of the genes may be selected for or against, unbalancing the possibility of using mtDNA for calibrating population age.
MtDNA clones itself rather than recombining. Because it is only through women that one can discern mtDNA, the potential for genetic drift and accidental loss of lines is very great. Each of the lines that are destroyed can never be taken into account by the analysis. Changes in population size through history, often quite considerable, exacerbate genetic drift and loss of mtDNA. One cannot assume the mtDNA variation is derived solely at a standard rate form the history of the population. Furthermore, Ingman (2000) points to the fact that all studies of mtDNA tend to be confined to the control region, which is less than 75% of the total amount of mtDNA. These studies are complicated by the extreme variation in substitution rates between sites and the consequences of parallel mutations causing difficulties in the estimation of genetic disturbance. Thus, making phylogenetic inferences from such data is difficult.
Therefore, while genetic analysis can be useful, it is full of complications that make it unreliable as a source of information if it is not corroborated by other types of analysis. Furthermore, in the case of our current question, it can only point to the fact that the colonisation of America occurred from Asia, the questions of how and when it occurred remains unanswered. To answer these questions, we need to combine genetic analysis of modern populations with alternative sources of data.
II.II Environmental Analysis
One of the most useful types of data can be found in archaeological sites. In Siberia, Yuri Mochanov excavated caves in Dyukhtai, where hunter-gatherers lived between 14,000-12,000 years ago. At this point in prehistory, sea levels were much lower than today, thanks to vast deposits of water being held in the glaciers and ice sheets that receded in later periods. This allowed a low-lying landmass called Beringia to link Alaska and Siberia up until 14,000 years ago when post-glacial warming began. It is across this that most archaeologists think the first colonisers came. To get to warmer climes after passing the land bridge of Beringia would be problematic for colonisers because the ice sheets of Cordilleran and Laurentide prevent southward movement. However, in 1950, it was discovered that there was an ice-free corridor that existed between the two sheets, and it is here that the colonisers are thought to have passed through.
A principle challenge for archaeologists working on the question of how the colonisers passed through the ice corridor is working out how they would have sustained themselves when travelling through it. One of the principle tools of analysis people have used to try to understand such a passage is comparative modern data. Renouf (1999:332), studying Newfoundland’s prehistory, observed that the small number of mammals had unpredictable periods of unavailability, due to an unstable food chain. For instance, the caribou numbers would crash regularly as wolves would attack caribou calves because snowshoe hares numbers crashed. However, such modern ethnographic study is problematic because we have no definite way to correlate the conditions of the modern studies with the environmental conditions of the ice corridor of the time.
Guthrie (1990) claims that this sort of tundra would be inhabitable. Using pollen samples from a volcanic ash field he discovered vegetation did exist during this time period, and posited by 15,000 years ago there would be woods in Alaska. Thus, we can see that during this period it may well have been possible to traverse the ice corridor. Pollen analysis (palynology) is a useful tool in archaeological analysis, giving an indication of the type of fauna that exists within a period. However, it is a very blunt tool, only giving the roughest of indications of the existence of plant life. This is because often certain species will be over represented in the faunal record, due to differential preservation rates. However, recent work in palynology has been more precise in gaining accurate assessments of what the Tundra ecology may have been like. However, without a site with which to associate the data, all we can do is speculate that it was indeed possible that the land bridge was crossed.
The alternative approach would be to go to America by boat. Archaeologists who support this view look at the depth and variety of Amerindian languages on the west coast opposed to the east as evidence of longer inhabitancy, theorising that the first colonisers moved along the west coast. A number of objections have been raised to this. The East coast may well have had as many languages as the West coast, but may have been more affected by the diseases (like small pox) that the Europeans brought with them and so more language groups may have been wiped out. However, it is important to remember that linguistic history is not necessarily the history of a people. A linguistic history is formed by a constellation of historical and political factors that make it unreliable as an indictor of inhabitancy or population movement.
It is not at all necessary that the first migration was by boat. While most of America’s coast would be too cold to support sea life capable of sustaining humans, there are a few islands that were found that could sustain life. However, most of those sorts of islands have now been submerged and in the absence of any archaeological data is seems hard to substantiate this theory. However, the problem with the land-bridge idea is the utter absence of archaeological data to support it. The earliest find in Alaska is dated at 11,800 years old, and was some flake blades that were assumed to come from Siberia. After that, the next universally recognised sites are the Clovis sites which are dated at between 11,200 and 10,900 years ago. It is from this that most theories about the colonisation of America originate.
Tags: America, colonisation, continents, homo sapien, migration, Pacific
