| Chiselling
away at the traditional way of thinking
Jacqueline
Nguyen
Biological anthropology
applies biological principles and approaches to the study
of humans. It examines how evolution has shaped us and
compares the way we look and behave with other primates.
Dr Darren Curnoe, a biological anthropologist in UNSW’s
School of Medical Sciences, is investigating human evolution
from a different point of view, opening up new avenues
and even revolutionising the way of thinking in anthropology.
Modelling
human evolution
In
collaboration with US primatologists and colleagues in
South Africa, Dr Darren Curnoe is using living vervet
monkeys and baboons to develop models of human evolution.
These primates are of interest in gaining insight into
our evolution because they share many similarities with
early humans. They are terrestrial, have varied diets
and are found in the same fossil sites as early humans.
“They appear in the fossil record around 3-4 million years
ago (MYA)
– about the time we see a lot of early humans in the fossil
record,” Curnoe says. “Like us, they have a very wide
distribution and are found in a range of habitats, yet
they’re essentially one species.”
Why
not use chimpanzees? Despite being the closest living
primate to humans, chimpanzees are not used in the team’s
research because no chimpanzee fossils have been found.
“Also, modern chimpanzees are restricted to the tropics
of Africa; so they don’t have a wide distribution. Whilst
they’re genetically much more similar, the Old
World monkeys are pretty close – about our fourth
or fifth cousins in the evolutionary sense.”
Looking out of Africa… and into East Asia
Curnoe
is also working with Dr Alan Thorne from the Australian
National University on a project that looks at the role
of East Asia in the evolution and origins of modern humans.
“We’re
looking at the last 500,000 years of human evolution in
East Asia, and trying to get a good handle on how important
East Asia is, because it’s been largely neglected,” says
Curnoe. “At the moment most of the focus and research
interest is on Africa and Europe because of the current
and dominant model that says that 100,000 years ago our
species evolved in Africa and left Africa.”
Curnoe
believes it is now time for a major synthesis of different
forms of information, from archaeology to anatomy to genetics,
to reconstruct the history of modern humans in East Asia
and Australasia.
Curnoe
thinks that there is very good evidence of biological
links between Australia and Asia. He explains that the
earliest Australians would have come from Asia, and that
the largest fossil sample for the whole of Asia is found
in Australia. The Australian fossil record is also very
good; therefore it provides a good sample of what was
going on broadly in Asia during that time period.
Curnoe
and Thorne hope to gain insight into human migration from
the fossil record. “What we’re trying to look at is where
there were other populations in East Asia at the time,
and we are curious – if people did leave Africa, what
happened when they met these (East Asian) people?”
Fossil
and archaeological excavations will be conducted, as well
as a major review and synthesis of the prehistory of East
Asia. Genetic studies will also be conducted to try to
put together a picture of what happened in East Asia over
this time period.
An example of a human evolutionary
tree. Over 25 species are recognised in the lineage,
many of which became extinct without making a genetic
contribution to modern humans.
Source: Smithsonian
Institution [external site] |
The
human evolutionary tree
Like
many other sciences, biological anthropology can be controversial,
especially because it is so close to home. Curnoe and
Thorne have studied the genetics of humans and chimpanzees
and how close they are using genetic distances.
“After
40 years of research, it is well established that we share
about 99% of our DNA. If we place that in a broad context
of mammalian genetics, that makes humans and chimpanzees
very, very close. We are sister species, which means that
we share a common ancestor, somewhere between 7-10 MYA.”
Curnoe
and Thorne are the first anthropologists to state that
humans and chimpanzees should be placed in the same genus,
Homo, based on their research. This raises important
ethical issues about how we view and treat other species,
particularly chimpanzees.
The
pair has taken this work further by coming to terms with
how many species there may actually be in the human evolutionary
line, given how close humans and chimpanzees are. “The
way we have done that is to try to get an idea of how
much genetic variation you’d expect to find within a species.
We’ve used this as a yardstick, as a measurement of trying
to estimate the number of species within the human evolution
line.”
“We’ve
come out and said, if you look at the genetics and given
the short distance between humans and chimpanzees, we
don’t believe it’s possible to have that many species,”
argues Curnoe.
Based
on genetic analyses, Curnoe and Thorne estimate that
there are far fewer number of species on the direct
line to modern humans.
Source: Curnoe & Thorne (2003) |
At
the moment over 25 different species are recognised from
the human fossil record. However the pair says there should
only be four on the direct line to living humans, and
a fifth that became extinct. The four species are H.
sapiens (including H. erectus), H. habilis,
H. africanus and H. ramidus.
“What
we’re talking about is subsuming a lot of the species
diversity into a much smaller number of species,” Curnoe
says. “If those 40 years of estimates and multiple studies
of human-chimp genetics are right, then it must have a
profound impact on the way we study human evolution.”
“We
try to do it slowly, chisel away at the old way of thinking
that says that there are many species, based purely on
anatomy – that anatomy of fossil groups is greater than
what we see in living humans today, therefore they must
be multiple species – is not necessarily the case.”
Curnoe's
investigations in new areas of biological anthropology,
from reconstructing early human history in East Asia to
pruning the human evolutionary tree, has shed more light
on the evolution of our species. His research contributes
to our understanding of human evolution and evolutionary
biology in general, as well as what it is to be human
and how we define ourselves.
Acknowledgments
OnSET
thanks Dr Curnoe for assistance with preparing this article.
See OnSET's
Career
Profile: Dr Darren Curnoe
References
Australian
Museum - Introduction
to Human Evolution website
Curnoe,
D. & Thorne, A. (2003) Number of Ancestral Human Species:
A Molecular Perspective. Homo, 53,
201-224
Eds
Jones, S., Martin, R., Pilbeam, D. (1992) The Cambridge
encyclopedia of human evolution. (Cambridge University
Press: New York)
Thorne,
A. Grün, R. Mortimer, G. Spooner, N.A. McCulloch,
M. Taylor, L. and Curnoe, D. (1999) Australia's Oldest
Human Remains: Age of the Lake Mungo 3 Skeleton. Journal
of Human Evolution 36, 591-612.
Wright,
L. (2003) Shaking the Evolutionary Tree. UNSW
Uniken Magazine, Issue 4.
Glossary
MYA:
Millions of years ago
Paleoanthropology:
The study of early humans and non-human primates,
and their evolution.
Archaeology:
The study of earlier human societies and cultures through
their material remains
Old
World monkeys: A diverse primate group found throughout
sub-Saharan Africa and southern Asia, for example macaques,
vervet monkeys, baboons, and colobus monkeys.
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