Outlining the problem.

Few topics have generated more debate and contro­ versy in the scientific literature over the past few years than the biological and behavioural origins of an a to ­ mically ‘m odern’ hum an populations: i.e. populations belonging to our own form of Homo sapiens sapiens. W hat is common ground in all these debates is that populations that were fundam entally ‘m odern’ in both a basic anatom ical sense, and in at least the m ajority of cultural and behavioural senses, were effectively established throughout all the m ajor regions of the Old W orld (i.e. Africa, Asia, Europe and parts of Australasia) by a t least 30-35 ka ago ( lk a = 1 0 0 0 years). T he curren t controversy hinges essentially on w hat happened before this time above all during the crucial formative phases of m odern hum an develop­ m ent between ca. 200 and 30 ka ago. It is this period which forms the m ajor battle ground of current debate over the evolutionary origins and m utual relationships of m odern world populations, and which provides the central focus of the present symposium. T hroughout the greater part of the present century effectively since the discovery of the ‘classic’ N ean­ derthal skeleton at La Chapelle-aux-Saints in 190 8 the issue of the biological and dem ographic origin of m odern hum an populations has been seen very largely as a dichotom y between two sharply opposed schools of thought. O ne view frequently referred to in the more popular scientific literature as the ‘G arden of E den’ or ‘N oah’s A rk’ hypothesis asserts that biolo­ gically and genetically m odern hum an populations evolved initially in one fairly limited and closely prescribed region of the world and subsequently dispersed at varying times to all other regions, either with or w ithout significant degrees of genetic interm ixture and interbreeding with the pre-existing populations within the same regions. At various points throughout the present century, and with varying degrees of emphasis, this view has been m aintained by (among others) M arcellin Boule, W illiam Howells and F. Clark Howell. M ore recently, workers such as G unter Brauer, as well as one of the present authors (e.g. Stringer & Andrews 1988), have focused a tten ­ tion on Africa as the particular continent of origin: the so-called ‘O ut of Africa’ model. The principal alternative scenario now generally referred to as the ‘m ultiregional evolution’ hypothe­ sis asserts that there was no such simple or discrete origin for the morphological and genetic character­ istics of m odern hum ans, and that hum an populations in all of the m ajor regions of the Old W orld (i.e. Africa, Asia and Europe) have pursued an essentially parallel pattern of evolution over at least the greater part of the past million years or so. C entral to the latter model, of course, is the assum ption that there was a sufficient degree of interbreeding and resulting gene flow between these geographically dispersed populations to m aintain a broadly similar pattern of evolutionary developm ent w ithin the different regions th roughout the whole of this time range. T he princi­ pal proponents of this hypothesis have been Ales H rdlicka, F ranz W eidenreich, C arleton Coon, Loring Brace and (more recently) M ilford W olpoff and Alan T horne (e.g. W olpoff 1989; T horne & W olpoff 1992). Potentially one of the most significant points of conflict between these two models relates to the character and timing of the divergence of the m odern patterns of regional (‘racial’) variation am ong pres­ ent-day populations. W hereas the population-disper­ sal hypothesis asserts tha t all of these divergences are the result of relatively short-term evolutionary pro­ cesses operating purely over the past 100 ka or so, the m ultiregional evolution viewpoint would trace these regional divergences back through a much longer timescale of at least several hundred thousand to one million years. It is hardly possible here to review the ebb and flow of debate between these two conflicting hypotheses over the past 80 years or so. Reviews of the earlier years of this debate have been provided by Frank Spencer (1984), and more recently by Smith et al. (1989). W hat can be said is that over the course of the past 10-15 years, a num ber of significant develop­ ments emerged which appeared to shift the balance of the evidence fairly strongly in favour of the former (population dispersal) scenario. O ne of these develop­ ments was the application of new dating methods. The use of the newly developed dating methods of therm o­ luminescence (t l ) to burn t flint and electron spin resonance (esr) to tooth enamel associated with the large samples of skeletal remains recovered from the two sites of M ugharet es Skhul and Jebel Qafzeh in northern Israel revealed that these fossils which had previously been generally assumed to be around 4050 ka in age in reality dated to around 100 ka (Grim & Stringer 1991; Aitken & Valladas, this symposium; Schwarcz & Grim, this symposium). Because these fossils had generally been accepted and described in the literature as showing modern features, this appeared to dem onstrate that such forms had appeared in at least one region of the world at a much earlier date than suspected hitherto, and dem on­ strably at a time when much more ‘archaic’ forms