Re: 'Out of Africa' still only a theory?!?!?

henry harpending (
29 Sep 1995 14:22:24 GMT

The real import of the mtDNA ("Eve") evidence is that it suggests we only had
several thousand ancestors for a long time and that the recovery from this
pinch started during the last interglacial. The arguments about the mutation
rate really aren't very significant, since if the time of the coalescent
("Eve") were a million years rather than 250,000 the suggested ancestral
population would be perhaps 20,000 rather than 5000. An older Eve would NOT
support regional continuity unless she were a whole lot older. The chimp
Eve is maybe several million years old (depending on one's idea of the mtDNA
transition/transversion ratio) implying that chimps did not go through such a

The "african origin" is supported by the greater african diversity in genetic
systems with high mutation rates (metrics, mtDNA, repeats) but NOT in low
mutation systems like nuclear markers. This implies that ancestors of
africans were successful first, but I don't see any evidence that this
happened in Africa which is pretty empty of archaeological evidence from 75
kya to about 25 kya or so.

The small number of human acestors has been known to population geneticists
for years, but anthropologists never paid any attention until the Eve fracas
was picked up by journalists. A nice discussion of recent evidence is a
column by Ann Gibbons in SCIENCE 6 January 1995 called "The mystery of
humanity's missing mutations".

Back to your point: if there were only a few thousand ancestors then such a
small number could not have been spread all over the globe. This is IMHO the
real genetic evidence for the african origin hypothesis. The topology of the
mtDNA tree, on the other hand, is bogus and unknowable I think. That the
root often seems to divide humanity into africans and non-africans is not
anything more than a reflection of the higher mtDNA diversity in Africa.

Henry Harpending, Penn State University

In message <44fmmn$> -
Richard pear) writes:

>Humans currently occupy every corner of the globe and I really don't
:>see why you would think that a less extensive occupation would be
:>unlikely in the past. The central problems with the Eve theory ("Out
:>of Africa") are that there is no evidence at all of any cultural
:>advantage held by the replacers, The biological evidence is suspect
:>(faulty cladograms, an unreliable clock) and ther *is* compelling
:>evidence of erectus/AMH continuity in a number of locations throughout
:>the world.