African Exodus--re-evaluating an hypothesis

Abstract

African Exodus: The Origin of Modern Humanity Christopher Stringer dc Robin McKie Henry Holt, 1997 That the authors of this book are from two different backgrounds suggests there may be some tension in the book. Christopher Stringer (paleoanthropologist at London's Natural History Museum) is a well known scientist, but Robin McKie is a journalist (science editor of The Observer). African Exodus is a politically correct history of mankind, devoted to defending the Out of Africa theory of human origins, and incidentally arguing that therefore all humans are basically identical. One can speculate that Stringer supplied the basic facts while McKie was responsible for the political gloss. The organization of the book is chronological, tracing human history from its origins. However, the first chapter is autobiographical, recounting the Stringer's first work on human skulls (done as part of his PhD thesis). It then describes how the Kibish skull from Ethiopia looked modern to him. Yet it dated to about 130,000 years ago (i. e. when Europe was inhabited by Neanderthals with quite different looking skulls). This led him to develop the Out of Africa hypothesis that modern humans had evolved in Africa, probably in East Africa, some of whom later moved out of Africa to populate the world. This chapter is followed by one arguing for the East African ancestry of modern humans, and then a couple of chapters on the Neanderthals and their replacement by Cro-Magnons. The next two chapters deal with the genetic evidence on human evolution and how that points to an African origin for humans. A chapter is devoted to the apparent intellectual advantages of the Cro-Magnons, and speculation as to just what they had that the Neanderthals lacked that led to their replacement. The part of the book devoted to reviewing hominid origins appears competent and is certainly very readable. It differs little from other popular accounts. It has the advantage of being more up to date than older ones, carrying the evidence of research into 1996. For instance, it provides a vivid account of the discovery of a Neanderthal infant by Rak (for a scientific description see Rak, Kimbel, & Hovers, 1994), seemingly too different from current Homo sapiens infants to be the same species. In one case, an interview brings the story more up to date even though the published work was not yet available. The genetic work of Tishkoff and Kidd on a CTI-r repeat on chromosome 12 is described. It provides very powerful evidence for an African origin of the hominids. (A published report is now available in Tishkoff, et al. 1996). Of course, there is always new genetic work, too new to be cited, notably that concerning the Y chromosome (Zerjal, et al. 1997 is a recent example). Unfortunately, the book went to press too early to give the important finding (Krings, Stone, Schmitz, Krainitzki, Stoneking, & Paabo, 1997) that Neanderthal mitochondrial DNA is sufficiently different from modern humans to make modern Europeans descent from Neanderthals unlikely. This finding greatly weakens the case for any multi-regional hypothesis of human origins in the form advanced by its contemporary exponents, when they argue that Cro-Magnons evolved from Neanderthals. Since the book went to press further evidence suggesting the Neanderthals were not the ancestors of current Europeans has appeared (Richards, et al., 1996, Schwartz & Tattersall, 1966, Holliday, 1967, Armour et al, 1996). The major errors in the book arise when it moves beyond paleoanthropology and attempts to be politically correct. I suspect McKie (a journalist) may have written these sections, although a co-author such as Stringer certainly deserves to share the blame for obvious errors. Stringer is the author of another recent book on a similar subject (Stringer & Gamble, 1993) which seems free of the political correctness problems of African Exodus. African Exodus digresses from paleoanthropology (Stringer's area of expertise) to attack The Bell Curve (Herrnstein, & Murray, 1994). …