i found this artical in the NewScientist web site..
Did we out-breed slow-maturing Neanderthals
Neanderthal women had just as much trouble in childbirth as modern women – and their kids took just as long to grow up.
Christoph Zollikofer and colleagues at the University of Zürich, Switzerland, have done the first three-dimensional reconstructions of the skulls of
a newborn Neanderthal from Russia, and two toddlers from Syria. They found that the newborn's cranium was the same diameter as a modern human's.
Neanderthal mothers had slightly larger birth canals, but the prominent face of Neanderthal babies made it just as hard to push out as a modern
This suggests that both groups had the social structures needed to help with childbirth. It also means, says Zollikofer, that a big brain at birth
must have evolved in some still-undiscovered common ancestor of modern humans and Neanderthals.
Moreover, conflicting estimates of Neanderthal growth rates based on teeth had led to disagreements about whether they grew up faster than us, amid
theories that a prolonged childhood allowed us to develop greater intelligence.
The new skull reconstructions show that Neanderthal babies grew 5 to 10% faster than modern humans. But since Neanderthals also had bigger bodies,
they took about the same time to reach adulthood that we do, says Zollikofer.
"The big question is, what happened to humans 50,000 years ago," he says. Early modern humans and Neanderthals now appear to have had similarly big
brains at birth, that grew at similar rates. But the brains of today's babies are smaller than both of them. "Are they more efficiently organised?
Or did we trade a bit of intelligence for smaller, cheaper brains that meant we could reproduce faster," he says.
If so, Zollikofer speculates, we may have succeeded the Neanderthals not because we were smarter, but because we bred faster – more like rabbits.
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0803917105)