I’ve been going back an forth with Bernard in
news sci.archealogy about the birthing.
Hi Bernard,
I’m not sure if I was that clear so I’ll try again. Neanderthals have larger heads than the groups they were contemporary with. I was curious if it was some adaptive advantage for them. Neanderthal women have a larger pelvis and probably a larger opening. Another guess was that they might have delivered children with larger heads. You said that it probably was not the case. I believe you but unsure why that is. So the question I posed, " Is it just that a specific adaptation by Neanderthal females would have taken too much time to adapt to a larger fetus?"
The intention of the question was to ask if Neanderthal birth head size is the same as moderns then why is that? Does the adaptation of getting to a larger birth head size take too long say an estimated 500,000 years which leaves out the possibility? The question assumes that Neanderthal children’s head sizes were getting larger for whatever the adaptive reason. Again the clumsily asked question asks if the possibility was thought not possible because such an adaptation would have taken too long to happen.
David Kirkpatrick
Marlborough, MASS
Bernards response:
This information taken from M.L. Weiss and A.E. Mann. 1990.Huamn Biology
and Behavior 5th ed. Glenview, IL :Scott foresman p. 432
Trouts1: This will probably not format correctly.
years ago name
skull size
3.5 million Australopithecus africanus 400-500 ml
2.0 million Homo habilis 500-775 ml
1.5 million Homo erectus 800 ml
1.0 million Homo erctus 1000 ml
200,000 early homo sapiens 1200-1300 ml
70,000 Homo sapiens neanderthal 1300-1700 ml
40,000 Homo sapiens sapiens (modern) 1350-1450 ml
A couple of things to notice. Remember that in a previous post I told you that in apes adult skulls are about two times the size of birth skulls. I also pointed out that apparently pelvic widths allowing about 350 ml to be born atre aboutthe limit a female can have and still walk upright on two
feet (a basic human characteristic). If early hominids were following the ape pattern ( reasonable assumption with common ancestors), the limit of this approach was reached about the time of H. habilis (1.5 MYA) (350 x2 =
700 ml). About this time a entirely new strategy developed, neoteny, giving birth at an earlier fetal stage so that more development will take place AFTER birth. Neoteny allowed later hominids to give birth to babies with 350ml or less skull volume and still end up with mature individuals with
larger skulls. Humans, as I pointed out< have 4 times as large adult skulls as birth skulls. Thus, H. erectus could have had babies with 250 ml skulls and still end up with adults at a 1000 ml.
What I am arguing is that Neanderthals did not have to evolve any adaptation the adaptation for neoteny had already taken place a million years before. Yes, Neanderthals had bigger skulls on the average than truly modern humans, but the range encompassed that found in modern humans
(1300-1700, compared to 1350-1450). There are humans who have skulls 2100 ml, and Anatole France’s skull was 1900 ml.
Apparently the average region of 1400 ml is sufficient for our needs and because it is 350 x 4 it also about the limit because it has no changed very much in the last 100,000 years.
I don’t think that Neanderthal women had wider pelvises than modern humans,
because their babies were neotenous and developed their ultimate brain sizes after birth.
I hope this helps.
Bernard Ortiz de Montellano