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Vertebrate and Hominid Evolution as a Response to Climate Change |
1 UMR CNRS 5561 et Laboratoire de Préhistoire et Paléoécologie du Quaternaire de l’EPHE, Université de Bourgogne, Centre des Sciences de la Terre, 6 bd. Gabriel, 21000 Dijon, France
2 Institut de Paléontologie humaine du Muséum National d’Histoire Naturelle de Paris, (UMR CNRS 9948), 1 rue R. Panhard, 75013 Paris, France jchaline{at}u-bourgogne.fr
A comparison of externalist and internalist approaches in hominid evolution shows that the externalist approach, with its claim that climate was responsible for the appearance of bipedalism and hominization, now seems to be ruled out by the biological, palaeogeographical, palaeontological and palaeoclimatic data on which it was based. Biological data support the embryonic origin of cranio-facial contraction, which determined the increase in cranial capacity and the shift in the position of the foramen magnum implying bipedalism. In the internalist approach, developmental biology appears as the driving force of hominid evolution, although climate exerts a significant influence and was involved in the following ways: (1) in the prior establishment of ecological niches that allowed the common ancestor to become differentiated into three subspecies; (2) by dividing up the area of distribution of species, resulting in the present-day subspecies of gorillas and chimpanzees; (3) by facilitating relative fluctuations of the geographical areas of distribution of the various species, particularly the spread of australopithecines across the African savanna from north (Chad, Ethiopia) to south (South Africa); (4) by determining adaptive geographical differentiations among Homo erectus and Homo sapiens (pigmentation, haemoglobin, etc.).
