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.