Evolution And History

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Reconciling the Evidence 209

conclusions are premature.^10 For one thing, the average
differences are not as great as those seen among living
subspecies of the single species of chimpanzee. For an-
other, differences between populations separated in time
by tens of thousands of years tell us nothing about differ-
ences between populations contemporaneous with each
other. More meaningful would be comparison of the DNA
from a late Neandertal with an early anatomically modern
European.
Finally, if we are to reject Neandertals in the ancestry
of modern Europeans because their DNA cannot be de-
tected in their supposed descendents, then we must also
reject any connection between a 40,000- to 62,000-year-
old skeleton from Australia (that everyone agrees is ana-
tomically modern) and more recent native Australians. In
this case, a mtDNA sequence present in an ancient human
seems to have become extinct, in which case we must al-
low the same possibility for the Neandertals.^11 In short, it
is definitely premature to use genetic evidence to remove
from modern human ancestry all populations of archaic
H. sapiens save those of Africa. Not even the Neandertals
can be excluded.

The Anatomical Evidence
Though the recent fossil discoveries certainly provide evi-
dence of the earliest anatomically modern specimens in
Africa, they do not resolve the relationship between bio-
logical change in the shape of the skull and cultural change
as preserved in the archaeological record. The changes in
the archaeological record and the appearance of anatomi-
cally modern skulls are separated by some 100,000 years.
The evidence from Southwest Asia is particularly interest-
ing in this regard. Here, at a variety of sites dated to be-
tween 50,000 and 100,000 years ago, fossils described as
both anatomically modern and Neandertal are present
and associated with Mousterian technology.
Nevertheless, recent African origins proponents argue
that anatomically modern peoples coexisted for a time
with other archaic populations until the superior cultural
capacities of the “moderns” resulted in extinction of the
archaic peoples. Especially clear evidence of this is said
to exist in Europe, where Neandertals and “moderns” are
said to have coexisted in close proximity between 30,000
and 40,000 years ago. However, defining fossils as either
Neandertals or “moderns” illustrates the difficulty with
defining a distinct biological species, given the presence of
variation found in humans.

The Genetic Evidence


Though genetic evidence has been the cornerstone of
the recent African origins hypothesis, molecular evi-
dence also provides grounds to challenge it. For exam-
ple, upon reanalysis, the molecular evidence indicates
that Africa was not the sole source of mtDNA in mod-
ern humans.^6 In addition, because both theories pro-
pose African origins for the human line, molecular data
could be interpreted as evidence supporting the African
origins of the genus Homo, rather than the more recent
species Homo sapiens. Both models place ultimate hu-
man origins firmly in Africa.
Other assumptions made by DNA analysis are prob-
lematic. For example, it is assumed that rates of mutation
are steady, when in fact they can be notoriously uneven.
Another assumption is that mtDNA is not subject to selec-
tion, when in fact variants have been implicated in epilepsy
and in a disease of the eye.^7 Another issue is that DNA is
seen as traveling exclusively from Africa, when it is known
that, over the past 10,000 years, there has been plenty of
movement of humans into Africa as well. In fact, one study
of DNA carried on the Y chromosome (the sex chromo-
some inherited exclusively in the male line) suggests that
DNA on the Y chromosome of some Africans was intro-
duced from Asia, where it originated some 200,000 years
ago.^8 Nevertheless, recent work on the Y chromosome by
anthropologist and geneticist Spencer Wells traces the hu-
man lineage to a single population living in Africa about
60,000 years ago.^9
Despite the seeming conflict, all of these data indicate that
gene flow has been an important aspect of human evolution-
ary history. The multi regional hypothesis and recent African
origins hypothesis differ in terms of whether this gene flow
occurred over the course of 200,000 or 2 million years.
Since 1997, studies of mitochondrial DNA have not
been limited to living people. In that year, mtDNA was ex-
tracted from the original German Neandertal remains, and
two other Neandertals have since been studied. Because the
mtDNA of each of these differs substantially from modern
Europeans, many have concluded that there can be no Ne-
andertal ancestry in living humans and that Neandertals
must constitute a separate species that went extinct.
But biological anthropologist John Relethford (a spe-
cialist in anthropological genetics) points out that these


(^6) Templeton, A. R. (1995). The “Eve” hypothesis: A genetic critique and
reanalysis. American Anthropologist 95 (1), 51–72.
(^7) Shreeve, J. (1995). The Neandertal enigma: Solving the mystery of modern
human origins (p. 121). New York: William Morrow.
(^8) Gibbons, A. (1997). Ideas on human origins evolve at anthropology gath-
ering. Science 276, 535–536.
(^9) Wells, S. (2002). The journey of man: A genetic odyssey. Princeton, NJ:
Princeton University Press.
(^10) Relethford, J. H. (2001). Absence of regional affinities of Neandertal DNA
with living humans does not reject multiregional evolution. American Jour-
nal of Physical Anthropology 115, 95–98.
(^11) Gibbons, A. (2001). The riddle of coexistence. Science 291, 1726.

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