Another little piece of information indicating that there are substantial differences between the two big-headed Homo species.
Tanya M. Smit et al., Dental evidence for ontogenetic differences between modern humans and Neanderthals. PNAS 2010. Open access.
Armed with state-of-the-art tomographic scanners, this paleontological team was determined to settle what previous research had only found inconclusive: whether Neanderthal development was faster paced or similar to that of Homo sapiens.
The results seem quite clear:
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| Fig. 3 (Predicted ages are derived from human radiographic calcification standards). |
Neanderthals, but not ancient H. sapiens, clearly deviate from the developmental pattern of our species, with teeth (and hence most likely all them) developing faster than among us.
It seems from this data that a 12 y.o. Neanderthal would be as developed as a 16 y.o. modern human. One can easily infer that they should reach puberty some 2-3 years earlier than we do, though this is not directly in the teeth and also shows some notable variability among modern humans.
The impression I get from the cranial development data, which the development data on the teeth doesn't contradict, is that there isn't a linear relationship between Neanderthal and modern human development.
ReplyDeleteIt is a bit like converting cat years to human years. I cat can live fourteen or even twenty years, but is sexually mature after a single year. Neanderthals appear to have reached adulthood much more quickly than modern humans, but to be quite stagnant developmentally once reaching adulthood.
I think that your supposition that they may have been sexually equivalent to a sixteen year old modern human at twelve isn't far from the mark. But, I also wouldn't be surprised if they pretty much reached full maturity and stopped developing at fourteen or fifteen (perhaps the human equivalent of being in one's early twenties) and stayed that way until menopause and old age symptoms started.
"It seems from this data that a 12 y.o. Neanderthal would be as developed as a 16 y.o. modern human"
ReplyDelete(Oh my God) I can't imagine neanderthals having children at 11 or 12...
But not all humans reach adulthood at the same time (I think that's obvious). For example, some girls are fully developed by 12-13, while others don't reach full maturity until early 20's.
I don't understand why these studies contradict each other so often. Another study told us neanderthals mature fast, but reached adulthood slower than us, because their brains were bigger.
Having bigger brains highly contradicts the idea of a faster development, it's a valid law for all animal kingdom.
"Another study told us neanderthals mature fast, but reached adulthood slower than us, because their brains were bigger".
ReplyDeleteReally?
"Having bigger brains highly contradicts the idea of a faster development, it's a valid law for all animal kingdom".
The comparison here is only with Homo sapiens. They surely did not develop faster than chimpanzees or cats.
However there are some irregularities and these are outlined in the abstract, when the authors mention earlier weaning in humans than in chimpanzees, which is at least a curious anomaly.
"Really?"
ReplyDeleteFinally, I could find the link:
"Neanderthal brain size at birth provides insights into the evolution of human life history"
Neanderthal brain size at birth provides insights into the evolution of human life history
Link missing. :(
ReplyDeleteLink missing. :(
ReplyDeleteSorry...
http://www.pnas.org/content/early/2008/09/06/0803917105.abstract
Got it, thanks.
ReplyDeleteI guess you mean this:
"the higher early brain growth rates and larger
adult brains of the Neanderthals compared with rAMHS have
interesting implications. The pattern of Neanderthal brain
growth fits into the general pattern of rate hypermorphosis in
this species: Compared with rAMHS, Neanderthals have been
shown to attain larger adult cranial sizes and more advanced
(peramorphic) shapes within a given period of ontogenetic time
(31). Rate hypermorphosis might be a correlate of greater
average body size in Neanderthals compared with rAMHS (21,
22). However, it does not imply earlier cessation of brain growth
(Fig. 4B), nor does it imply a faster pace of life history (as was
suggested in refs. 18 and 19): In light of the maternal energetic
constraints hypothesis (2, 5), our results suggest that Neanderthal
life history had a similarly slow pace as that of rAMHS, and
probably was even somewhat slower".
Right?
"Right?"
ReplyDeleteExactly :)
Full text is available. This study makes more sense to me than the other one. If neanderthals had larger brains it's quite difficult to accept they were fully developed by 14-16. This of course doesn't mean that there were no minor differences.
It's all pretty confusing, clearly more studies are needed to clarify this, because in the list of exclusive H. sapiens genes, I don't remember any linked to a slower development, but again, the genome it's not yet complete.