On the hairs of the legs

2014/06/30 Galarraga Aiestaran, Ana - Elhuyar Zientzia

• Eboluzioa
• Anatomia/Fisiologia

With the start of summer, hairs become enemies, especially for women and in some places (like heads). That's right, and one more year there seems to be no change, although in spring there was intense debate about hair removal and, above all, about the elimination of leg hairs. The supporters especially highlighted hygiene and aesthetics, while the opponents exposed varied motifs, from the feminist point of view to the doctor.

For reasons, there is still an unanswered question: Why do we have hairs between the legs if we have lost many other parts of the body throughout evolution?

To answer, scientists have looked at the evolution of a parasite: the louse. They have discovered that the louse of our head (Pediculus humanus capitis) and the louse of the body of chimpanzees come from the same ancestor. Ours adapted to the hair of our head and could not extend to the body until we started wearing the clothes. Then the body was colonized and became Pediculus humanus corporis.

But the prickly lice have another origin. It belongs to the species Pthirus pubis and its ancestor is the same as that of the louse of the body of the gorillas. In addition, this ancestor is not so old, so scientists have concluded that the hair of the paw has occurred after the loss of the body. For what? What is its function?

Scientists have several hypotheses: that it is an ornament to attract the other sex, which serves to transmit sexual pheromones... But they still don't know and continue to investigate. And we, meanwhile, cannot use it as a reason for or against hair removal...