Neanderthals died out some 30,000 years ago. They were likely the
closest relative we humans — Homo sapiens — ever had. Now, a new study
suggests that Neanderthal women had a somewhat different birth canal
from modern women, but giving birth probably wasn't any easier.
A
year ago, a researcher at Florida Atlantic University used fossils to
create a computer simulation of what a Neanderthal voice might sound
like. According to Robert McCarthy and his team, it sounded more human,
perhaps than a dog or bird, but a long way from modern human speech.
In
February, scientists in Germany announced a rough draft of the
Neanderthal genome, which they said showed great similarities with
humans, though no sign of interbreeding.
And now, a researcher
at the University of California at Davis has analyzed pelvic bones from
Neanderthal fossils. Dr. Tim Weaver concluded that birthing babies was
just about as difficult for Neanderthal women as it is for modern
humans.
"The size of the birth canal was about the same as in
modern humans," says Weaver, "and we know from other lines of evidence
that Neanderthal babies would have had about the same size heads and
sort of the same size bodies as modern humans."
That's a very
tight fit. In fact, human babies have to twist and turn on their short
trip out of the womb. But Weaver says the Neanderthal birth canal was
shaped a bit differently thanks to a wider pelvis, allowing a more
straightforward birthing process.
"The interesting thing that
we concluded is that the baby would have just passed straight through
the birth canal without rotating at all."
Weaver came to his
conclusions by analyzing Neanderthal skeletal remains. The trouble is,
the pelvic bones don't survive very well. In fact, he had only one
Neanderthal to work with, so he needed to do some clever, high-tech
manipulation after putting fossilized bone fragments through a medical
CAT scanner.
"And what you can do is you can make a virtual
image of the fossils, and then you can do things like mirror fossils
from, say, the left side of the body and mirror them over to the right
side of the body, and then sort of like a jigsaw puzzle, you can kind
of try to fit those pieces together to try to get a more complete
representation of, in this case, what the pelvis would look like."
Our
Homo sapien ancestors originated in Africa, a much warmer region than
Europe, which was the principal homeland of the Neanderthal. In cold
climates, natural selection favors a shorter, more compact body to stay
warm, and Weaver says that may explain the different birth canals.
"People
[today] who have ancestry near the equator tend to have a narrow
pelvis. We think that this is related to thermo-regulation; it's good
to have a narrow body in a warm climate because it helps you dissipate
heat. And so there's sort of these ecological rules that apply to many
different species, and we think that they also applied to Neanderthals
and sort of contemporaneous Homo sapiens that were living at the same
time as Neanderthals."
For our human ancestors, in other words,
developing in warmer parts of Africa, a lean body was an advantage,
even though the narrower pelvis required that rotation of the baby
through the birth canal. Neanderthals, living in cooler places, favored
a wider pelvis that allowed the baby to exit the womb more directly -
though it was still a tight fit.
Dr. Tim Weaver of the University of California wrote about that in the Proceedings of the National Academy of Sciences.
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