In the 1970s, archaeologists thought they had a good idea of how the world was settled, and, in particular, their understanding seemed to supersede the older idea that humans had spread out from a single source during the upper palaeolithic.
[Today] many authorities believe that...leptolithic [upper palaeolithic] man (of the modern species, Homo sapiens sapiens) was the direct descendant of the Neandertalers. Such a view contrasts strongly with the earlier opinion that the leptolithic cultures were brought to Europe by an immigration from the Near East of H. sapiens, who wiped out the earlier and 'inferior' Neandertal population.David and Ruth Whitehouse, Archaeological atlas of the world, 1975, p. 39.
This view has itself now been superseded, and the latest genetics research is taking us back to the original idea, that humans originated in one place and, from there, colonised the rest of the planet.
Clear genetic trees for both modern Y chromosomes and mtDNA point back to a recent common ancestor of all modern humans within the last 200,000 years and a migration out of Africa less than 100,000 years ago. This new line rather quickly replaced all pre-existing human genetic lines, including the Neanderthals...[T]here is no convincing evidence for [interbreeding] in our male and female gene lines.Stephen Oppenheimer, Out of Eden: The peopling of the world, 2004, p. 347.
It would be premature to assume that we now have perfect knowledge and that the latest ideas will not be superseded in their turn. Genetics is a new tool, and in the rush to apply it there has been little attention paid to its limitations, which will gradually come to light. The development of understanding is a process of successive refinement. It will not be complete until history itself comes to an end.
A major reason why ideas about early human migrations (or any other aspect of the past) keep changing is that they focus on material evidence and often on only one kind of such evidence (pots, genes). Material remains can never provide a full record of the living, breathing past, and will always leave ambiguities. To round them out, it is necessary to take account of everything we know, from contemporary and historical experience, about how societies function. Although some archaeologists do study modern farmers and hunter-gatherers in order to understand those of the past, what I am really referring to is the kind of total historical theory based on abstract theoretical principles to which this website is devoted. Such a theory, treating all human experience as one, will allow us to build a more reliable understanding than comes from concentrating on pots, genes or whatever kind of evidence might come along in future.
Humans have always wondered how they got to be where they are now. Many peoples have foundation myths in which their ancestors arrived from somewhere else. The Aztecs recalled their origins on the North American plains. Many Andean societies believed they had emerged from underground. Some Maori tribes celebrate the ancestor Kupe who first came to New Zealand. The English, and to a lesser extent some continental European nations, link themselves to barbarian invaders who plundered the collapsing Roman Empire.
These traditional stories are often fantastical in their details, and they leave such questions as whether an invading group replaced the original population or merely superimposed the thin layer of a conquering elite.
In the early twentieth century, archaeology appeared to be shining the light of science on the problem. The distinctive styles of ancient artefacts (e.g. shape/decoration of pots and tools) seemed to demarcate distinctive cultures associated with different human groups. When artefacts of a particular style were found to spread from one area to another, this was assumed to reflect a displacement or expansion of the people of the corresponding culture.
By the later twentieth century, theorists began to doubt the formerly confident conclusions they had arrived at in this way. It was recognised that the diffusion of cultural objects did not necessarily require the movement of people. Artefacts might travel along trading networks, or one group's styles might simply be adopted by its neighbours. Archaeologists went almost to the opposite extreme, denying the possibility of population movement at all.
Today the evidence and its implications remain uncertain. The main conclusion is the sheer complexity of the interactions and travels of prehistoric peoples.
- The Beaker Folk were once deemed to be recognisable by their pottery (see picture, right) and related artefacts, and the spread of Beaker objects in the third millennium BC was thought to represent a wave of technologically advanced people colonising much of north-western Europe. Later, it was thought to represent just the transmission of the technology and an associated belief system. The modern thinking is that both aspects played some part, though any migration was tentative and targeted, not the sweeping motion once envisaged.
- The Anglo-Saxons were long thought to have invaded Britain after the collapse of the Roman Empire, bringing a new language, religion and way of life, and driving the original Britons west into Wales and Cornwall. This is the story we have from Bede, who lived within a couple of hundred years of the events. It seemed to be confirmed by the appearance of new kinds of artefacts in the archaeological record, around the relevant time. However, the archaeological evidence has come to look problematic, with close intermingling of the supposed 'British' and 'Anglo-Saxon' material, and some of the changes taking place apparently before the time of the alleged invasion. In the last decade or so, it has been increasingly argued (by both professional and amateur theorists) that there never were any Anglo-Saxon invasions, and the distinction between eastern 'English' and western 'British' has existed in Britain from Mesolithic times. This is despite explicit references to an invasion in contemporary sources (e.g. the Gallic Chronicle of 452, under the year 408). Most historians and archaeologists would today be cautious about making firm statements in any direction.
The genetics approach makes use of haplotypes, i.e. specific markers in mitochondrial and Y-chromosome DNA, which are inherited in only the female and male lines respectively, and which embody a precise record of a person's ancestry. For a clear description, see this charts and diagrams website. The technique was also discussed in an earlier post, where I mentioned my suspicion that the flaws in its assumptions will be revealed in due course.
The Genographic Project, a National Geographic website, presents an Atlas of the Human Journey, based on the new genetic findings, and allows you to get your own DNA tested and your origins worked out.
Before the use of haplotypes came along, human genes had already been studied for a long time by another method. This is population genetics, which considers the genes on ordinary chromosomes that can be passed down by either the male or female line. Unlike the haplotype technique, population genetics offers few easy answers and creates a complicated picture.
Population geneticists are sceptical of the new arguments of the haplotype researchers. At a 2005 symposium, geneticists working on haplotypes were invited to analyse an artificial dataset whose 'ground truth' was known. While it was agreed the precise results would not be revealed, it has been admitted they were less than spectacularly successful (see Simulations, genetics and human prehistory, ed. S. Matsumura et al., p. 192).
Another indication that haplotype data may be more ambiguous than its practitioners care to acknowledge is the fact that commercial companies offering ancestral DNA testing have been found to give inconsistent results. The biochemical reactions extracting the DNA profile are presumably precise and repeatable, but the significance of the results is more a matter for opinion and interpretation.
None of this is to say the new genetic methods, or indeed traditional archaeology, are useless for understanding early human migrations. The point is simply that we should take the latest pronouncements on this subject with a pinch of salt. We are still in the early stages of unravelling this aspect of our past.