Development of Human Hair Differences

 Development of Human Hair Differences

The exact hair shape (phenotype) of our early hominid predecessors is unknown. It is presumed that during the gradual process by which our immediate ancestor homo erectus began a transition from furry to Naked skin, hair texture changed from straight (the condition of most mammals, including all apes) to a more wavy form, or even a curled phenotype, which arrived with modern humans and is assumed to be the result of environmental pressures and / or sexual selection. It is not clear at what point classical subequatorial African tightly curled hair evolved, but it many be a late development due to climatic changes.

 

 

Straight hair appears to be a new trait in human evolution and is associated with newly emerged genetic alternatives 9alleles) in both the genes which provide strength to the hair follicle, trichohyalin (TCHH) and gene which is important for synthesizing proteins, the ectodysplasin A receptor (EDAR) gene. This latter gene is common in East Asians but not Africans and Europeans.

 

The EDAR gene is responsible for the East Asian hair type, and arose during the past 65,000 years, when early humans were migrating out of Africa into Europe and then Asia. The distribution of these straight hair related alleles supports a hypothesis that our human ancestors developed curly hair compared to other primates. The straight hair found in East Asia and the Indo-European subgroups almost certainly developed independently of each other.