Mitochondrial Eve - Implications of Dating and Placement of Eve

Implications of Dating and Placement of Eve

Initially there was a lot of resistance against the Mitochondrial Eve hypothesis. This resistance was due, in part, to the popularity of the Multiregional Evolution hypothesis amongst some leading paleoanthropologists such as Milford Wolpoff. This prevailing theory held that the evolution of humanity from the beginning of the Pleistocene 2.5 million years BP to the present day has been within a single, continuous human species, evolving worldwide to modern Homo sapiens. More resistance came from those who argued that there was too little time between Homo erectus and modern Homo sapiens to allow for another new species, and others who argued that for regional evolution from archaic hominin forms into modern ones. Consequently, the finding of a recent maternal ancestor for all humans in Africa was very controversial.

Cann, Stoneking & Wilson (1987)'s placement of a relatively small population of humans in sub-saharan Africa, lent appreciable support for the recent Out of Africa hypothesis. The current concept places between 1,500 and 16,000 effectively interbreeding individuals (census 4,500 to 48,000 individuals) within Tanzania and proximal regions. Later, Tishkoff et al. (2009) using data from many loci (not just mitochondrial DNA) extrapolated that the Angola-Namibia border region near the Atlantic Ocean is likely to be near the geographical point of origin of modern human genetic diversity. In its relatively southern origin proposals, this autosomal study was considered by the authors to be broadly consistent with a previous mitochondrial DNA studies, including one by some of the same authors which associated the origins of mitochondrial haplogroups L0 and L1 with "click languages" in southern and eastern Africa.

To some extent the studies have already revealed that the presence of archaic homo sapiens in Northwest Africa (Jebel Irhoud) were not likely part of the contiguous modern human population. In addition, the older remains at Skhul and Qafzeh are also unlikely part of the constrict human population, evidence currently indicates humans expanded in the region no earlier than 90,000 BP. Tishkoff argues that humans might have migrated to the Levant before 90 Ka, but this colony did not persist in SW Asia. Better defined is the genetic separation among Neanderthals, Flores hobbit, Java man, and Peking man. In 1999 Krings et al., eliminated problems in molecular clocking postulated by Nei, 1992 when it was found the mtDNA sequence for the same region was substantially different from the MRCA relative to any human sequence. Currently there are 6 fully sequenced Neanderthal mitogenomes, each falling within a genetic cluster less diverse than that for humans, and mitogenome analysis in humans has statistically markedly reduced the TMRCA range so that it no longer overlaps with Neandertal/human split times. Of all the non-African hominids European archaics most closely resembled humans, indicating a wider genetic divide with other hominids.

Since the multiregional evolution hypothesis (MREH) revolved around a belief that regional modern human populations evolved in situ in various regions (Europe: Neandertals to Europeans, Asia: Homo erectus to East Asians, Australia: Sumatran erectines to indigenous Australians), these results demonstrated that a pure MREH hypothesis could not explain one important genetic marker.