Darwin, evolution, science and archaeology - part 2

Posted May 10th, 2009 by Andrea Vianello

In my previous post of just a few days ago I was mentioning how few news had attracted my attention so far this year. I am therefore only too happy now to see the publication of researches relevant to archaeology catching up with other disciplines. In the 8th of May issue of Science (p. 730-1) Martin K. Jones and Xinyi Lu of the McDonald Institute of Archaeological Research report on the Origins of Agriculture in East Asia. This is another study based on genetic and scientific evidence very much connected with evolution. The authors have examined the domestication of wheat, barley, rice and millet and found that although the actual process might have dated back to about 10,000 years ago, if not even earlier, the fixation of genes (i.e. their permanent presence in the genome of the plant from generation to generation) determining the type of stems occurred much later. The process of domestication initially altered only the stem and its efficiency at retaining the seeds, low efficiency for wild spreading and high efficiency for dependency on human action. Domesticated rice in China for instance becomes genetically separated by wild varieties around 4,500 years ago, suggesting that for millennia rice was cultivated only as a very partial source of food. The change for farmers had to be gradual. Of interest is also the evidence for millet: it spread faster and wider than the other plants already about 7,000 years ago, from China to the Black Sea and beyond. Cereals instead spread into China between 4,000 and 5,000 years ago. The spread of the domesticated varieties of plants resulted in genetic changes due to different patterns of production and consumption. More people benefited from cultivated crops, though this was achieved by spreading production and consumption rather than increasing consumption locally.
In a recent paper by Terence A. Brown, Martin K. Jones, Wayne Powell and Robin G. Allaby, The complex origins of domesticated crops in the Fertile Crescent (direct link to PDF file), the case for a multiregional and gradual emergence of plant domestication is set very clearly. Moreover, archaeobotanical research (listen to the podcast by Dominique de Moulins on archaeobotany) is revealing that whilst the spread of agriculture appears to be closely linked to the genetic fixation of the morphological changes to the stem, and that the spread of domesticated plants started more subtle processes of adaptation of the plants to new environments. Such processes never stopped, and are still ongoing. Thus, whilst the actual genetic change of plants to the domesticated variety was in place at least for rice and cereals around 10,000 years ago, only the affirmation of long-distance exchanges, in the third and especially second millennium BC, established a situation where cultivated crops could make a difference to the living of people. It is also worth mentioning that the cultivation of maize in Mesoamerica; potato, peanut and manioc in the lowland and highland regions of South America; rice in the Yangtze region of southeast Asia; and cereals in the Fertile Crescent, a region comprising the valleys of the Tigris, Euphrates and Jordan rivers in southwest Asia started at the same time, suggesting a transfer of technology before the establishment of long-distance exchanges of material products. It seems difficult to overstate the importance of communications and exchanges among humans in front of this evidence: trade rather than agriculture may have revolutionised the ancient world.

Charles Darwin famously had difficulties in convincing people that human beings descend from apes. We now accept that in an extremely far past, our ancestors had ape-like characteristics. In a very distant past, I wish to stress. What about a different human species that become extinct only 20,000 years ago or less, as it seems the case of Homo floresiensis? Contemporary palaeoanthropologists are facing the same disbelief today as that faced by Darwin and best known for the emblematic attack to the theory of evolution as it was worded by Bishop Wilberforce on the 30th of June 1860 at Oxford (some background on this in three pages, respectively by J. R. Lucas; J. H. Brooke; and the Natural History Museum). The 7th of May issue of Nature reports on new evidence supporting the case of Homo floresiensis being a separate human species. A study of the fossilised foot of Homo floresiensis, and one on insular dwarfism in hippos have re-heated the debate. Of particular interest seems to me the second paper, since it proves that the brain of mammals can shrink far more than expected if necessary, and in the case of the bovid Myotragus this was up to 50%. Of course, the human brain being such a distinctive feature of human beings, thinking that evolution could have experimented until fairly recently in reducing its size can make people uncomfortable. It should be remembered however, that the human brain increased in size until the Neandertals, and decreased in anatomically modern humans (see my paper for an extended discussion and references) and therefore we already knew that bigger was not better in this particular case. So much is unknown about the human brain that nothing should surprise us.

Evolution is very much a hot topic for archaeological research in 2009, and I am very happy of this. Recent researches are offering new understandings on a variety of themes, and posing new questions as well. Hopefully these researches will also demonstrate once for all that archaeology is also, and very much so, a science. For a comprehensive choice of the Internet’s best websites on archaeological sciences check out our database. For a full list of resources ordered by headings, see the home page.