Washington, Apr 23 (ANI): A new study has suggested that Neanderthal women had equally tough time giving birth to big-headed babies as modern humans, but the infants did not have to rotate to get out like they do in human mothers.
Modern women's birth canals are oval, change shape halfway down the birth canal so that they are widest from front to back at the bottom, near the pelvic outlet.
Thus, the baby has to rotate its head to fit as it moves through the birth canal.
If a baby fails to rotate, another part of its body, such as its shoulders, hands, or feet, may obstruct the birth canal, which is painful and dangerous for the mother and infant.
Paleoanthropologist Timothy Weaver of the University of California, Davis, thought the shift to this more complicated rotational birth predated the split between modern humans and Neanderthals.
This is because Neandertals, which lived until 30,000 years ago in Europe, also had big heads and, presumably, used the same evolutionary strategy to deliver their big-brained babies.
And, to test the ideology, researchers made a new virtual reconstruction of the pelvis of a Neanderthal woman.
The researchers got permission to make computed tomography-scans of the pelvis, which is kept at the British Museum in London and they could refit the pieces of the pubis, ischium, and ilium together in a three-dimensional, virtual reconstruction.
They also used landmarks on the pelvic fragments to compare the pelvis to those of modern humans, and to predict the size and shape of the missing pieces, such as the sacrum and dimensions of the pelvic outlet.
The reconstruction suggests that the pelvis of the Tabun Neandertal was widest from side to side all the way down the birth canal, more like that of Homo erectus or australopithecines than modern humans.
Thus, they concluded that although Neandertal mothers still had difficult births because of their babies' large heads, their babies did not rotate in the womb.
And the reason behind such evolution, according to researchers could be that they had to balance pressures to adapt to the hot climate in equatorial Africa--and tall, slender-hipped humans thermoregulate in the heat better than short, stocky humans (whose physiology retains heat better in the frigid latitudes).
By evolving a birth canal that is wide front to back, our ancestors could accommodate both narrower pelvises and the delivery of big-brained babies.
"Given the poor preservation of the Tabun pelvis, ... this is a bold claim," said anthropologist Marcia Ponce de Leon of the University of Zurich in Switzerland.
However, she does agree with one conclusion: "Birth was equally difficult in Neandertals as in modern humans," with or without a twist.
The study is published online in the Proceedings of the National Academy of Sciences. (ANI)