Humans are significantly less hairy compared to our primate relatives primarily because of changes that occurred in our genetic makeup during evolution.
The Evolutionary Process of Hair Reduction
While we still possess the genes necessary for producing hair across our bodies, the instructions these genes provide for hair growth underwent significant alteration over time. Think of genes as instruction manuals for building and maintaining an organism. In our case, the instructions for dense body fur were effectively edited out or deactivated.
How Genes Changed
According to evolutionary science, during our evolutionary history, those genes mutated and stopped sending fur-making instructions. Gene mutations are changes in the DNA sequence. These changes can happen randomly, and if they provide a survival or reproductive advantage, they are more likely to be passed down through generations. In the case of human hair reduction, mutations occurred in genes that control hair follicle development and density, leading to a reduction in overall body hair.
The Timeline
This remarkable transformation didn't take millions of years in the typical sense of macroevolution. Our hair loss might have happened over merely a hundred-thousand to a few million years – a relatively short period in the grand scope of evolutionary history.
Summary
In essence, the reason humans are less hairy boils down to specific gene mutations that occurred during our recent evolutionary past, which led to the deactivation or alteration of the instructions needed for producing dense body fur like that of other primates.
