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Human evolution at
the crossroads: Integrating genetics and paleontology
Barlow, Life Sciences Editor
SEATTLE — Advances
in genetics during the last decade not only have influenced modern medicine,
they also have changed how human evolution is studied, says an anthropologist from the University of Illinois at Urbana-Champaign.
Using her own research on the teeth of baboons as a case in point, Leslea
J. Hlusko said that some of the traits considered important to human
evolution, such as the thickness of molar enamel, may be too simplistically
interpreted by some paleontologists.
Hlusko organized a Monday symposium on human evolution at the annual
meeting of the American Association for the Advancement of Science.
She brought together experts who study phylogenetics, ancient DNA, developmental
genetics, quantitative genetics and primate evolution so that they could
share the same stage to discuss their current work, and where they may
be able to go on together in an effort to understand the evolution of
our ancestors. The session was discussed Sunday at a news briefing.
Hlusko’s call for an integration of paleontology and genetics
is also the focus of a perspective article that will appear online Monday
ahead of print publication by the Proceedings of the National Academy
"Data from developmental genetics and biomedicine, coupled with
advances in computer technology, now provide us with a wealth of new
information from which to better understand the genetic and non-genetic
influences underlying primate, including human, evolution," Hlusko
said in an interview. "By combining these different data sets with
the fossil record, we don’t have to be just paleontologists, or
just geneticists. Because selection operates on the genome through our
anatomies, it makes better sense to conduct our research with a similarly
integrative approach. Recent advances in genetics have now made this
method more feasible for primate studies. "
Research on early hominids, she argues, has benefited from an abundance
of new fossil finds, but the emerging data are leading to competing
interpretations of human origins and evolution instead of providing
clarity. Research that integrates paleontology and genetics may provide
some resolution to these debates, she said.
As an example, her recent study of teeth in more than 400 savanna baboons
housed at the Southwest Foundation in San Antonio shows that, contrary
to long-held assumptions, enamel thickness varies widely within a population.
She and her colleagues also found that the underlying genetic architecture
may have enabled rapid evolutionary changes in enamel thicknesses that
could reflect changes in dietary habits over time.
The study, published online ahead of print by the American Journal of
Physical Anthropology, is the largest genetic analysis of primate enamel
thickness done so far.
"People have assumed that it is hard to change certain traits –
that if an organism has evolved thick enamel, its descendents cannot
easily go back to thin enamel," she said. "The thinking has
been that if hominid fossils 5 million years old have thick enamel,
they are human ancestors. If they have thinner enamel, they must be
That assumption, Hlusko said, "may be over simplified." Using
their baboon study, Hlusko and colleagues argue that "when used
uncritically, enamel thickness has the potential to confound rather
than to clarify phylogenetic studies of higher primates."
The Monday morning
AAAS session reflects a desire to "see integrative paleontological
and genetic approaches as the norm rather than the exception in primate
and human evolutionary studies," Hlusko said at a news briefing
on Sunday. This integrative approach was first developed by scientists
working outside the study of primates, such as Rudolf Raff of Indiana
University, also a participant in the AAAS symposium. One of the goals
for the symposium and Hlusko’s PNAS article is to highlight the
application of integrative biology to human evolutionary studies.
"Although many of the scientists currently involved in this integrative
approach are united by their common interest in human evolution, I’ve
realized over the last few years that many of us sometimes seem to speak
different languages," she said.
"We often think
about genetics and evolution from very different perspectives,"
Hlusko continued. "These conceptual divides lead to a bit of isolation
and separation, and are actually holding back progress in both research
and training. This symposium will give us an opportunity to come together
and talk across our differences."
The true advancement in the understanding of human evolution will come
primarily from two sources, Hlusko said: recovery of new fossils (fieldwork);
and the integration between genetics, development and paleontology.
Speakers in the symposium who discussed their current research, in addition
to Hlusko, a paleontologist incorporating quantitative genetic approaches,
were Alan Walker of Pennsylvania State University, a primate paleontologist
who discussed efforts to understand contradictory paleontological and
genetic phylogenies; Chi-hua Chiu of Rutgers University, who gave a
developmental genetics perspective on human evolution; and Hendrik Poinar
of McMaster University in Canada, who studies the molecular components
extracted from ancient fossils (ancient DNA).
Speaking in more general terms about the current state of integrated
hominid paleontological/genetics research and where it may be headed
were Kenneth M. Weiss of Pennsylvania State University, a developmental
geneticist, and Raff, the author of the 1996 book "The Shape of
Life: Genes, Development and the Evolution of Animal Form," and
founder of "EvoDevo" (evolutionary-developmental biology).