Abstract
The process of hominization involves an increase in brain size. The development of hominids’ cognitive capital up to the emergence ofHomo sapienswas due to interactive, iterative, and integrative coevolution, allowing positive selection. Although this depends on many factors, in this position paper we show three categories that stand out: gene mutations, food resources, and cognitive and behavioral stimulation.Australopithecusbenefited both from the inactivation of theGULOanduricasegenes and from bipedalism causing the cognitive capital of theHomo genus to develop advantageously. This evolution depended on two factors. Firstly, a triggering factor: gradual climate change.Homostarted to regularly consume meat in addition to plants and insects. Secondly, a stimulating factor: mutations in theFADS2gene, which encodes Δ6-desaturase; a key enzyme for the synthesis of DHA and sapienic acid. The polymorphism of this gene appears to have been essential in allowing theHomo genus to adapt to its food, and for its evolution. It provides an undeniable advantage in terms of the productivity of fat synthesis (DHA), and may partly explain positive selection. With the advent of cooking and new mutations producing even moreFADS2, the brain reached its maximum size inHomo neanderthalensis, in a food ecosystem that provided favorable quantities of α-Linolenic acid and DHA. However, the Würm glaciation upset this equilibrium, revealing its fragility as regards to the brain and fertility.Homo sapiens, benefiting from new variants of theFADS2gene, were able to adapt to this harsh environment, whereas Neanderthal man was unable to do so and became extinct.
Highlights
The hominization process consists in the gradual transformation of a line of hominoids into Homo sapiens
There are few studies devoted to the evolution of the brain as it relates to physiological evolution, certain gene mutations, and the food resources used in certain key biochemical mechanisms
The results show that modern humans have two haplotypes – A and D – for the FADS cluster defined by 28 simple nucleotidic polymorphisms (SNPs)
Summary
The hominization process consists in the gradual transformation of a line of hominoids into Homo sapiens. The process lasted over 4 million years, beginning when the group of hominoids leading to man separated from the group that led to chimpanzees This hominization includes all the structural and behavioral changes that led to the characteristics of modern-day humans. The increase in brain size and encephalization quotient (the ratio of brain mass to total body mass) (Williams, 2002) are essential characteristics of hominization These increases began from the Homo genus onwards, approximately 1.9 million years ago. There are few studies devoted to the evolution of the brain as it relates to physiological evolution, certain gene mutations, and the food resources used in certain key biochemical mechanisms This evolution over the course of 40 million years was iterative, interactive, and integrative, with an acceleration over a period of 2 million years
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