Neanderthal Hybrid
Implications of Neanderthal-Homo Sapiens Hybrid by Abrigo do Lagar
Velho.
In a recent excavation at Abrigo do Lagar Velho in Portugal,
Duarte et al
(1999) unearthed what was later to be recognized as early human
skeletal remains
which pointed to interbreeding between Neanderthal and
Modern Humans during the
mid - upper Palaeolithic transition. The morphology
of the remains, belonging to
a child of approximately 3-4 years old,
indicates a Neanderthal typology in
post-cranial features, and more modern
cranial features. The find has been cited
as evidence of hybridization
between the two traditionally separate human lines,
and offers an explanation
to the question of Neanderthal extinction. (Trinkaus
1999)
Anthropologists are now offered a line of evidence pointing to
the
contemopranity of Moderns and Neanderthals in parts of Europe and
assumptions
can be made about their contact: "The discoverers...are making
a
ground-breaking claim, that the skeleton shows traces of both Neanderthal
and
modern human ancestry, evidence that modern humans did not simply
extinguish the
Neanderthals, as many researchers had come to think.
Instead the two kinds of
human were so alike that in Portugal, at least, they
intermingled...for
thousands of years." (Kunzig, 1999) By examining the
theories of human
evolution, and looking at the cultural evolution of tool
technology as well as
the biological transitions and differences between the
two types of humans, we
can see that this hybridization just might be the
answer. Perhaps this find will
be able to tell us what exactly did happen to
the Neanderthals. Firstly, it is
useful to have an overview of the different
theories of human evolution, or I
should say the two most widely accepted
views as accepted by palaeo-anthropologists
in the field. For some years now
it has been the contention that the origins of
modern humans stem from either
a continuous evolution from archaic to modern
humans in local regions from an
earlier dispersal of Homo erectus, or conversely
from modern humans evolved
in Africa only which then dispersed to replace those
hominids in said
regions. These two theories are known as the Continuity or
Regional model
and the Replacement or Out of Africa model respectively. The
fossil
(skeletal) and cultural (technological) evidence thus far has pointed
to
convincing arguments on both sides, which proponents are quick to
defend.
Neanderthals can be distinguished from anatomically Modern Humans
by the
presence of prominent brow ridges, low forehead, occipital bun,
facial
prognathicism, large nasal aperture, and shorter, sturdier skeletal
features
most notably, distinguishing them from Moderns who were taller and
had longer
limbs, higher foreheads, lass prominent browridges and rounder
skulls. It should
be noted that the cranial capacities of both were
comparable, with the
Neanderthals being even slightly larger. (Klein:
1989) Many proponents of a
regional theory claim that such morphological
differences show a continuity and
depending on how they are viewed can be
seen as evidence of variation within a
species, not distinct species. This
would mean that the Neanderthal morphology
developed as an adaptation to the
colder glacial climate of Europe and
elsewhere. (Wolpoff:1980) From a
replacement standpoint however, these
differences in morphology are too
distinct to be variables on a theme and in
conjunction with dates provides
evidence supporting that view. (Mellars and
Stringer:1989) Neanderthals
occupied Europe and the Middle East during a time
range usually agreed upon
as ranging from roughly 130 kya - 35 kya to as recent
as approx. 26kya.
Modern populations are seen as early as 100kya in the Middle
East and
around 40 kya in Europe. At some sites in the middle east, both
populations
lived in very close proximity to one another for what is thought to
be a time
range of about 40 000 years. (Akazawa et al:1998) Recent developments
in
genetic studies have begun to open new lines of evidence in the
relatedness
of Neanderthals to current modern human populations. By studying
the genes of
both, we can compare the similarities and differences and
calculate whether the
two are close enough to say there is a relation or not.
This line of research
had been theory mostly because the skeletal remains on
record had no organic
material available from which to extract genetic
material (i.e.: collagen in the
bone). DNA from a Neanderthal specimen would
be able to confer or oppose the
" Mitochondrial Eve" theory put forth by Cann
et al in 1987 (Foley and
Lahr 1992: 526; Klein 1989:352) which stated
that the common ancestor for modern
human populations could be traced to
approx. 200kya in Africa. When DNA was
finally extracted from a Neanderthal
specimen, this could be addressed. The DNA
in question, retrieved from the
original Neanderthal find from Neander Valley,
is mitochondrial. Mitochondria
have their own DNA outside of the nucleus and are
inherited only through the
mother. Unlike nuclear DNA, mitochondrial DNA (mtDNA)
does not recombine with
reproduction. The variation that exists between two
mtDNA sequences is
instead solely the result of mutation. Because mutations are
thought to occur
at a set rate, the amount of time that has passed since two
mtDNA sequences
diverged can be calculated). Researchers can then trace the
lineage of that
gene, and find how old it is, or rather how far back that
particular gene
goes. The results from the Neanderthal mtDNA show an ancestor
which goes back
much farther in time in Africa, and would seem to refute any
connection with
Modern populations after that time. There are some flaws with
the mtDNA
studies though and further research is needed. Other lines of
genetic
research include R.M. Harding's studies which look at variation in
the
betaglobin gene Harding found that one major betaglobin gene lineage,
thought to
have arisen more than 200,000 years ago, is widely distributed in
Asia but rare
in Africa, suggesting that archaic populations in Asia
contributed to the modern
gene pool. Studies of the Y-chromosome by M.F.
Hammer, indicate migrations back
and forth into Africa. (Harris and Hey
1999:84) In a nutshell, the technological
differences between Neanderthal
middle Palaeolithic technology and the Modern
upper Palaeolithic technology
can be narrowed down to flake and blade
technologies. The transition between
the two can be viewed again as either
gradual or sudden. Some middle
Palaeolithic tools in Europe, the Middle East and
Africa, regardless of
the hominids associated with them can show a variety of
technologies.
Certainly, at about 30 000 years ago, there was a shift in
technologies to
include art and personal adornment along with the finer
micro-blade
technologies. However, it is debatable as to whether these features
were
practiced by preceding Neanderthals or whether these innovations were
brought
into Europe by Moderns who would replace them. (Thorne and
Wolpoff:1992)
The question of the transition from the middle to upper
Palaeolithic surrounds
whether or not the transition was gradual or sudden.
Evidence of burials within
Neanderthal populations indicates that such
cultural indicators were derived
from those populations by other successive
modern populations. The remains
discovered by Duarte et al at Abrigo do Lagar
Velho in Portugal "present a
mosaic of European early modern human and
Neanderthal features" according
to Erik Trinkaus (1999). It is this blending
of features that implies
interbreeding between the two. It could be that the
replacement model is
somewhat supported in that it was the hybrid which
gradually replaced pure
Neanderthals, or that the regional model is
somewhat supported in that the
Neanderthals, or rather their descendants,
indeed became fully modern. The
translation of this evidence depends on who
is looking at it, and what view they
support in the first place. This brings
up the issue of bias in the field and
indicates that the study by its nature
cannot be exact and is certainly open to
interpretation. It is apparent that
there can be no consensus as yet to the fate
of the Neanderthals. Arguments
on both sides can be quite compelling, but
perhaps the most compelling is
that of the third hypothesis, the middle ground,
being that there needs to be
further investigation into the possibility of
hybridization between
Neanderthal and Modern populations. Erik Trinkaus, staking
his reputation on
the claim, has lent his support to this hypothesis: "If
you have two
populations of hunter-gatherers that are totally different species,
that are
doing things in very different ways, have different
capabilities--they're not
going to blend together," Trinkaus says.
"They're going to remain separate.
So the implication from Portugal is that
when these people met, they viewed
each other as people. One group may have
looked a little funny to the other
one--but beyond that they saw each other as
human beings. And treated each
other as such." (Kunzig 1999) Evidence which
could be used to corroborate
such a theory include further DNA research,
including both mitochondrial and
nuclear extractions if possible. Obviously one
sample from a single specimen
is not enough to base a clear argument on. Perhaps
with more research, the
archaeological record will be corroborated by the
biological record, and show
that indeed the transition from mid to upper
Palaeolithic was gradual and
due to the interbreeding of two types of humans,
which replaced the local
population from which much of the technology was
derived. Further excavations
which produce similar remains as that of Abrigo do
Lagar Velho may also
show increasing evidence of hybridization. Only by seeking
to expand the
fossil record, and exacting reliable dates will we be able to tell
the whole
story of human evolution, for which the Neanderthal question is but a
small
part. By answering this question though, we can piece together the real
story
of our origins and begin to understand the whole picture of
hominid
evolution.
Bibliography
Bower, B. 1993 Neanderthals
take a big step back in time. Science News
143(15):228-230. Flanagan,
Ruth. 1996 Out of Africa. Earth.5(1): 26-35. Harris,
E.E. and J. Hey 1999
Human demography in the Pleistocene: Do mitochondrial and
nuclear genes tell
the same story? Evolutionary Anthropology 8(3): 81-86. Klein,
Richard G.
1989 The Human Career. Chicago: University of Chicago Press. 1992
The
archaeology of modern human origins. Evolutionary Anthropology 1(1):
5-14. 1998
Why anatomically modern people did not disperse from Africa
100,000 years ago.
In Takera Akazawa, Kenichi Aoki and Ofer Bar-Yosef,
editors, Neanderthals and
Modern Humans in Western Asia, New York,:
Plenum Press, pp. 509-521. Kunzig,
Robert. 1999 Learning to love
Neanderthals. Discover 20(8): 68-75. Leitzes,
Nicholas 1994 Brutes or
brothers? Earthwatch: The Journal of Earthwatch
Institute 15(3): 22-26.
Mellars, Paul 1995 Neanderthals in perspective.
Antiquity 68(260):
656-658. Rouhani, Shahin. 1989 Molecular genetics and the
pattern of human
evolution: Plausible and implausible models. In P. Mellars and
C.
Stringer, editors, The Human Revolution. Princeton: Princeton
University
Press, pp. 47-61. Shreeve, James. 1994 Phenomena: Comments and
notes.
Smithsonian 25(6): 7-9. Stoneking, Mark and Rebecca L. Cann. 1989
African origin
of human mitochondrial DNA. In P. Mellars and C. Stringer,
editors, The Human
Revolution. Princeton: Princeton University Press, pp.
17-30. Stringer, C.B.
1989 Documenting the origin of modern humans. In
Erik Trinkaus, editor, The
Emergence of Modern Humans: Biocultural
adaptations in the later Pleistocene.
Cambridge: Cambridge University
Press, pp. 67-96. 1998 Chronological and
biogeographical perspectives on
later human evolution. In Takera Akazawa,
Kenichi Aoki and Ofer
Bar-Yosef, edotors, Neanderthals and Modern Humans in
Western Asia, New
York,: Plenum Press, pp. 29-37. Stringer, C.B., J.J. Hublin,
and B.
Vandermeersch. 1984 The origin of anatomically modern humans in
Western
Europe. In Fred H. Smith and Frank Spencer, editors, The Origins
of Modern
Humans: A World Survey if the Fossil Evidence. New York: Alan
R. Liss, Inc., pp.
51-135. Tattersal, Ian and Jeffrey H. Schwartz. 1999
Hominids and hybrids: The
place of Neanderthals in human evolution.
Proceedings of the National Academy of
Sciences. 96(13): 7117-7119.
Thorne, A.G. and M.H. Wolpoff 1992 The
multiregional evolution of humans.
Scientific American 266(4):76-83. Trinkaus,
Eric 1989 Issues concerning
human emergence in the later Pleistocene. In Erik
Trinkaus, editor, The
Emergence of Modern Humans: Biocultural adaptations in the
later Pleistocene.
Cambridge: Cambridge University Press, pp. 1-17. 1999 The
early Upper
Paleolithic human skeleton from the Abrigo do Lagar Velho (Portugal)
and
modern human emergence in Iberia. Proceedings of the National Academy
of
Sciences. 96(13): 7604-7609. 1999 Direct radiocarbon dates for Vindija
G1 and
Velika Peina Late Pleistocene hominid remains. Proceedings of the
National
Academy of Sciences. 96(22): 12281-12286. Wilson, A.C. and R.L.
Cann 1992 The
recent African genesis of humans. Scientific American 266(4):
68-73. Wolpoff,
Milford H. 1980 Palaeoanthropology. New York: Alfred A.
Knopf. 1989 The place of
Neanderthals in human evolution. In Erik
Trinkaus, editor, The Emergence of
Modern Humans: Biocultural adaptations
in the later Pleistocene. Cambridge:
Cambridge University Press, pp.
97-141. Also see:
http://www.anatomy.usyd.edu.au/danny/anthropology/
sci.anthropology.paleo/archive/september-1995/0106.html