Hair for brain trade-off, a metabolic bypass for encephalization.

Bibliographic Collection: 
Publication Type: Journal Article
Authors: Dror, Yosef; Hopp, Michael
Year of Publication: 2014
Journal: Springerplus
Volume: 3
Pagination: 562
Date Published: 2014
Publication Language: eng
ISSN: 2193-1801

Hair loss in humans is perplexing and raises many hypothetical explanations. This paper suggests that hair loss in humans is metabolically related to encephalization; and that hair covered hominids would have been unable to evolve large brains because of a dietary restriction of several amino acids which are essential for hair and brain development. We use simulations to imply that hair loss must have preceded increase in brain size & volume. In this respect we see hair loss as a major force in human evolution. We assume that hair reduction required favorable climatic conditions and must have been quick. Using evolutionary and ecological time scales, we pinpoint hair loss to a period around 2.2-2.4 million years ago. The dating is further supported by a rapid selection at that time of the sialic acid deletion mutation which may have protected growing human brains against calcium ion flux. In summary we view encephalization, in part, as a metabolic trade-off between hair and brain. Other biochemical changes may have intervened in the process too; and the deletion mutation of sialic acid hydroxylation may have been involved as well.

DOI: 10.1186/2193-1801-3-562
Alternate Journal: Springerplus