Lone Survivors by Chris Stringer

maximum, coinciding with the last known records of the Neanderthals or their stone tool industries in places like Gibraltar and the Crimea. Such stressful conditions would no doubt have affected both Neanderthal and Cro-Magnon populations, sharpening the competition for diminishing resources in environments where their ranges overlapped. But only Homo sapiens came through those crises.
    A rather more sophisticated modeling of conditions in Europe when the last Neanderthals overlapped with the Cro-Magnons was published in 2008. In this work William Banks and his colleagues used the location of stone tool assemblages dated between about 37,000 and 42,000 years, which were thought to identify the presence of Neanderthals or Cro-Magnons in particular regions. Then, treating the distributions as though they represented a species of mammal rather than stone tools, they used ecological modeling to reconstruct the environmental preferences and tolerances of the two populations, and the ranges they each should have been able to occupy at the time, according to those preferences. The time span covered two mild phases interrupted by a short but severe cold snap at about 39,000 years. This was not when the Campanian Ignimbrite was deposited farther to the east, but when the Atlantic was chilled for several hundred years by the southward flow of an armada of icebergs (a Heinrich event , discussed further in chapter 4).
    The results showed that, before the cold snap, the Neanderthals should have been widely distributed, and indeed they were. During the Heinrich event, both populations shrank in their modeled and actual distributions, in the face of the environmental deterioration. But when conditions ameliorated at about 38,000 years, although the warmer and wetter conditions should have encouraged both populations, the moderns bounced back while the Neanderthals did not. The modeling also showed that the Neanderthal and Cro-Magnon populations were attempting to exploit similar ecological niches; in practice the moderns increased the breadth of theirs through time, at the expense of the Neanderthals. While in the earlier phases the modern niche did not include central and southern Iberia, as time went on the Cro-Magnons increasingly expanded southward toward outposts of Neanderthal survival such as Gibraltar.
    This interesting work shows how such modeling can be done, and it should be possible to further refine the analyses, as ultrafiltered radiocarbon dates and the use of correlation tools like microtephra become increasingly available. A more direct attempt to estimate the relative population sizes of the last Neanderthals and the first moderns in western Europe came from the Cambridge archaeologists Paul Mellars and Jennifer French. They mined a large data set recording the extent in area of each of the last Neanderthal sites in southwestern France and those of the succeeding Aurignacians in the same region. Similarly they compared data on the number of stone tools each human population left behind in their sites, and the amount of food debris they generated. Multiplying all these together, they concluded that the early modern population was about ten times the size of the preceding Neanderthal one. This might imply that the moderns swamped the Neanderthals, but at the moment we can’t reliably place them together as direct competitors in the European landscape over any precise length of time, only infer that they probably did coexist.
    As I have come to realize, we should not be looking for a single cause for Neanderthal extinction anyway; we need to take a wide view of this. The fascinating events that took place in western Europe some 35,000 years ago get most of the scientific and popular attention, but they were only the endpoints of hundreds of thousands of years of evolution and potential interaction between the lineages of modern humans and the Neanderthals (for example, ancestral populations could have been in contact