Last month the find of a Homo erectus fossil skull at Dakanihylo Ethiopia
was announced. The original article is Berhane Asfaw, et al, “Remains of
Homo erectus, from Bouri, Middle Awash, Ethiopia,” Nature,
416(2002):317-320, p. 317
On the ASA list Dick Fischer posted a very short note essentially
announcing the discovery to the list but not going into the implications of
that discovery.
http://www.calvin.edu/archive/asa/200203/0404.html
There has been no further discussion of that discovery. This note will try
to make clear the importance of this discovery.
Over the past 20 years, about half of the anthropologists have taken a
position that separated the Asian erectus from the African version of the
same creature. They called the African variety Homo ergaster. Tattersall
was one of the proponents of this view. He writes:
"Hard on the heels of these species comes Homo ergaster, which,
as the 'Turkana Boy' attests, is postcranially altogether more
modern. . . . On the other hand, what is
very clear, at least to me, is that H. ergaster is not the same
thing as the classic Homo erectus from eastern Asia. A related
species, yes; but the African form is more primitive than the
Asian one, and it deserves recognition as a distinct species." ~
Ian Tattersall, The Fossil Trail (New York: Oxford University
Press, 1995), p.231
There are two main issues which this discovery impacts on. First, is the
question of whether H. ergaster was a different species from Asian H.
erectus which, was claimed, went extinct without issue. In this view, modern
man arose from African alone. This view rests upon the difference between
the Asian and African erectines. For ergaster to be a different species,
there must be a clear divergence in the traits of the two varieties with no
contemporary intermediates. The second issue is the ability of small
populations of the genus Homo to interbreed across vast distance. This
second issue is of importance in answering the question of whether
anatomically modern man coming out of Africa around 100 kyr ago replaced all
the archaic hominids or interbred with them.
The finding of a skull in Africa which is of Asian affinities says one of
two things. We either had a long distance traveler a million years ago and
thus, he is a tourist or the ergaster and erectus varieties are just that,
varieties of the same species. When the discoverers of the Daka skull
compared it with both ergaster and erectus of similar age, they couldn't
clearly separate it from either side (Asfaw, et al 2002, p. 318)
This made this skull an contemporary intermediate and thus unlikely to be a
tourist. This data indicates that ergaster and erectus are merely extremes
(minor ones at that) of the same population. The authors state:
“Regardless of the software parameters used, or the removal of the later
Asian demes, the hypothesis of a deep cladogenesis between African and Asian
H. erectus is unsupported by our analyses (Fig. 2). Previous cladistic
efforts have noted difficulty with the African OH 9 specimen because it
consistently aligned with the Asian fossils, thereby being interpreted as a
sort of Tanzanian outpost of 'Asian' morphology or as an evolutionary
intermediate. The recovery of the Buia and Daka fossils, almost certainly
from the same eastern African deme, compounds such problems. Like OH 9,
these new African specimens share many derived characters with Asian and
European specimens. As a consequence, the cladistic method, regardless of
serious questions concerning its applicability here, fails to support the
division of H. erectus into Asian and African clades. Whether viewed
metrically or morphologically, the Daka cranium confirms previous
suggestions that geographic subdivision of early H. erectus into separate
species lineages is biologically misleading, artificially inflating early
Pleistocene species diversity. Rather, the Daka calvaria is consistent with
the hypothesis of a widespread, moderately polymorphic and polytypic species
at 1.0 Myr.” Berhane Asfaw, W. Henry Gilbert, Yonas Beyene, William K.
Hart, Paul R. Renne, Giday WodeGabriel, Elisabeth S. Vrba and Tim D. White,
“Remains of Homo erectus, from Bouri, Middle Awash, Ethiopia,” Nature,
416(2002):317-320, p. 318
This implies that the erectines of a million years ago were able to maintain
enough genetic mixing from Africa to Asia to remain a similar species. And
this gets to the most important issue.
One of the most important pieces of evidence against regional continuity
(the idea that there was sufficient gene flow across the ancient world to
maintain the hominids as a single species is the small breeding population
determined from genetics. Relethford states the problem:
“The genetic evidence suggests no more than 10,000 reproductive-aged adults
throughout much of our species’ history. If true, then it is difficult to
imagine how so few people could have been spread out over several continents
and remained connected by gene flow as required by the multiregional model.
" John H. Relethford, Genetics and the Search for Modern Human Origins, (New
York: Wiley-Liss, 2001), p.146
Relethford answers the question by showing that the breeding population is
not the ecological population. The breeding population constitutes about 1/3
to 1/2 of the population (p. 147) and that there may have been more females
than males in the breeding population which would further expand the
ecological population. (p. 148). So much for the theoretical issues.
The Daki skull shows that somehow the ancient hominids actually did maintain
gene flow across such a large area. And if they did it 1 million years ago,
it is not out of the question for mankind later to have done the same thing.
And this is the real importance of the Daki skull; it challenges one of the
prime supports for the Out of Africa view of mankind, in which there was no
interbreeding between the anatomically modern peoples and the ancient
hominids. The Daki skull opens the possiblity that genetic contributions to
the ancestors of modern humans came from everywhere.
One other interesting piece of information which sheds some light on this
issue is Alan Templeton's recent work which showed that:
"". . . human populations in Africa and Eurasia have not been genetically
isolated from one another, but rather have been interchanging genes for
least 600,000 years," Professor Templeton said."
http://news.independent.co.uk/world/science_medical/story.jsp?story=271688
His original article can be found at: Alan Templeton, “Out of Africa Again
and Again,” Nature, 416(2002):45-51
For the Christian, if we ignore this evidence of ancient connection with
pre-anatomically modern hominids, we will be doing no better than the YECs
do with the age of the earth.
glenn
see http://www.glenn.morton.btinternet.co.uk/dmd.htm
for lots of creation/evolution information
anthropology/geology/paleontology/theology\
personal stories of struggle
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