September 21, 2009

Climate influence on morphological differentiation of humans


Anat Rec (Hoboken). 2009 Aug 28. [Epub ahead of print]

Climate Signatures in the Morphological Differentiation of Worldwide Modern Human Populations.

Hubbe M, Hanihara T, Harvati K.

The ability of cranial morphology to reflect population/phylogenetic history, and the degree to which it might be influenced by environmental factors and selection pressures have been widely discussed. Recent consensus views cranial morphology as largely indicative of population history in humans, with some anatomical cranial regions/measurements being more informative on population history, while others being under selection pressure. We test earlier findings using the largest and most diverse cranial dataset available as yet: 7,423 male specimens from 135 geographic human population samples represented by 33 standard craniometric linear measurements. We calculated Mahalanobis D(2) for three datasets: complete cranial dataset; facial measurement dataset; and neurocranial measurement dataset; these morphological distance matrices were then compared to matrices of geographic distances as well as of several climatic variables. Additionally, we calculated Fst values for our cranial measurements and compared the results to the expected Fst values for neutral genetic loci. Our findings support the hypothesis that cranial, and especially neurocranial morphology, is phylogenetically informative, and that aspects of the face and cranium are subject to selection related to climatic factors. The Fst analysis suggest that selection to climate is largely restricted to groups living in extremely cold environments, including Northeast Asia, North America, and Northern Europe, though each of these regions appears to have arrived at their morphology through distinct adaptive pathways.



Anonymous said...

I consider it more important for peoples living in very cold environments to adapt metabolically to the cold rather than their cranial morphology. Most peoples living in cold environments wear various head coverings to lessen the effects of the cold on their heads.

Australians are mostly of Northern European origin, and many immigrants are also of Northern European origin yet they have poor adaptation to cold. Their bodies are still geared to living in tropical environments like most humans irregardless of their head morphology. Asian immigrants seem just as poor in their cold adaptations.

Gregory76 said...

The maps showing the distribution of most morphological features show that the distribution mostly corresponds the distribution we would expect given the climate and the kind of features that are selected for in that climate. This holds true even though other factors, such metabolism and clothing, are much more important.
There are exceptions, as among the leptomorphs of northern Europe and the Mongoloids and Amerinds in the tropics, and these then give us reason to postulate the existence of a migration of another climate, and we already have plenty of good reason for this in the latter two cases.