Macaques and chimps are still used in anthropology and neuroscience as “primitive models” for human evolution. This is of course a non-sense: all living species, after the divergence from a common ancestor with modern humans, have evolved and changed as humans did. The genus Macaca is as young as the genus Homo, and living macaques and living humans are recent species in evolutionary terms, approximately with a comparable age. The problem with chimps is that we miss fossils, so we ignore how and how much their lineages has changed. But we have more information on macaques, and in general on fossil cercopithecoids. A very detailed and informative study on the endocast of Victoriapithecus has been recently published, definitely a stimulating and comprehensive article for primate paleoneurology. This Old World monkey, dated to 15 Ma, had a small cranial capacity and large olfactory bulbs, but a sulcal pattern similar to modern cercopithecids. This suggests two major points. First, in Old World monkeys sulcal complexity evolved before brain size increase. Second, brain morphology evolved in cercopithecoids and hominoids through distinct processes, mixing primitive traits, different mechanisms, specific adaptations, and some convergences. These results stress further the necessity of caution and of a proper evolutionary perspective when dealing with comparative primatology and human brain evolution: macaques (and chimps) are derived species as we are, with their own independent evolutionary histories. They can provide information on biological factors which are shared among our respective lineages, but it would be an error to think that their anatomy, physiology, or genetics, represent an ancestral condition.
Posts Tagged 'endocranial volume'
Tags: Cercopithecoids, cerebral complexity, endocranial volume, olfactory bulb
Tags: Australopithecus, endocranial volume, fossil endocasts, Simon Neubauer
Cranial capacity estimations and inferences in fossil species suffer two main limits: incompleteness of the endocranial anatomy and small sample size. Neubauer and colleagues have now published a very detailed paper on these factors, by using Australopithecus africanus as case-study. They provide new figures for the endocranial volume of this taxon, quantifying the effect of incompleteness and small samples on the estimations. This is not only useful to enhance our knowledge on australopiths’ cranial capacity, but it represents a real quantitative advance in paleoneurology as scientific discipline.