20. Human Diversity and Its History
303
apparent in several nuclear genes (Harding et a1. 1997; Hey 1997; Zietkiewicz et a1.
1998). Recently, however, there have appeared several papers analyzing STR polymorphisms (Shriver et a1. 1997; Di Rienzo et a1. 1998; Kimmel et a1. 1998; Reich
and Goldstein 1998). These all find strong evidence of a major population expansion in our history. Given the new findings, it seems safe to go back to the mitochondrial estimates of the timing of this expansion: these vary from 120000 to
30000 years ago, with heterogeneity among populations. Uncertainty about mtDNA
mutation rates is great, so these numbers should be treated with caution.
Can we relate the expansion visible in our DNA to anything in the fossil and
archaeological records? There are at least four candidates for the correspondence.
First, Mode 3 stone tool technologies appear about 250 000 years ago in Africa and
Europe!. Second, human fossils that are equivocally modern appear in Africa and
the Levant 100000 or more years ago associated with Mode 3 technologies. Third,
the Toba super-eruption at 71 000 years ago may have caused widespread ecological devastation and extinction on earth, and the expansion may be recovery from
that event (Ambrose 1998). Fourth, there is a dramatic invasion of Europe by bearers of Upper Paleolithic (Mode 4) technologies 40000 years ago. We do not believe
that there is compelling evidence favoring any of these alternatives.
2.3 Dispersal of Modern Humans
In Europe and western Asia north of the Himalayas there is a clear record of the
spread of modern humans from Africa. Most of Europe was occupied rapidly although pockets of Neanderthals apparently persisted for millennia, even adopting
some of the new tool technologies.
South of the Himalayas the record is not so clear. If there was a separate southern exodus there is little record of it until Australia, which was occupied between
35000 and 40000 years ago (O'Connell and Allen 1998) by bearers of Mode 3
technology. Mode 4, thought by many to be diagnostic of modern humans, never
appeared in Australia. There are at least two scenarios about the history of Australia that are plausible.
The first scenario is that there was a southern branch of the human expansion
that did not bear Mode 4 technologies, implying that Mode 4 is not a marker of
modern humanity but only a marker of a society where males were not continuously
engaged in parental investment.
In a famous paper the Whitings (Whiting and Whiting 1975) point out that
there are consistent differences between societies where males are familial and those
where males are "aloof' from women and the family. In the latter males are more
I Modes refer to a regular sequence of complexity of stone tools made by humans and human
ancestors during the Pliocene and Pleistocene (Clark 1977). Mode 1 is pebble tools, Mode 2
adds the Acheulian hand axe technology, Mode 3 contains flakes made from prepared cores,
Mode 4 is the technology of the Upper Paleolithic with blades and worked bone, and Mode
5 is the microlithic technology associated with the Mesolithic.
303
apparent in several nuclear genes (Harding et a1. 1997; Hey 1997; Zietkiewicz et a1.
1998). Recently, however, there have appeared several papers analyzing STR polymorphisms (Shriver et a1. 1997; Di Rienzo et a1. 1998; Kimmel et a1. 1998; Reich
and Goldstein 1998). These all find strong evidence of a major population expansion in our history. Given the new findings, it seems safe to go back to the mitochondrial estimates of the timing of this expansion: these vary from 120000 to
30000 years ago, with heterogeneity among populations. Uncertainty about mtDNA
mutation rates is great, so these numbers should be treated with caution.
Can we relate the expansion visible in our DNA to anything in the fossil and
archaeological records? There are at least four candidates for the correspondence.
First, Mode 3 stone tool technologies appear about 250 000 years ago in Africa and
Europe!. Second, human fossils that are equivocally modern appear in Africa and
the Levant 100000 or more years ago associated with Mode 3 technologies. Third,
the Toba super-eruption at 71 000 years ago may have caused widespread ecological devastation and extinction on earth, and the expansion may be recovery from
that event (Ambrose 1998). Fourth, there is a dramatic invasion of Europe by bearers of Upper Paleolithic (Mode 4) technologies 40000 years ago. We do not believe
that there is compelling evidence favoring any of these alternatives.
2.3 Dispersal of Modern Humans
In Europe and western Asia north of the Himalayas there is a clear record of the
spread of modern humans from Africa. Most of Europe was occupied rapidly although pockets of Neanderthals apparently persisted for millennia, even adopting
some of the new tool technologies.
South of the Himalayas the record is not so clear. If there was a separate southern exodus there is little record of it until Australia, which was occupied between
35000 and 40000 years ago (O'Connell and Allen 1998) by bearers of Mode 3
technology. Mode 4, thought by many to be diagnostic of modern humans, never
appeared in Australia. There are at least two scenarios about the history of Australia that are plausible.
The first scenario is that there was a southern branch of the human expansion
that did not bear Mode 4 technologies, implying that Mode 4 is not a marker of
modern humanity but only a marker of a society where males were not continuously
engaged in parental investment.
In a famous paper the Whitings (Whiting and Whiting 1975) point out that
there are consistent differences between societies where males are familial and those
where males are "aloof' from women and the family. In the latter males are more
I Modes refer to a regular sequence of complexity of stone tools made by humans and human
ancestors during the Pliocene and Pleistocene (Clark 1977). Mode 1 is pebble tools, Mode 2
adds the Acheulian hand axe technology, Mode 3 contains flakes made from prepared cores,
Mode 4 is the technology of the Upper Paleolithic with blades and worked bone, and Mode
5 is the microlithic technology associated with the Mesolithic.