Deleterious recessive alleles, such as the allele that causes cystic fibrosis, can persist in a population indefinitely. Why aren’t these rare alleles eliminated completely?

answer:

convection currents in the magma drive plate tectonics. heat generated from the radioactive decay of elements deep in the interior of the earth creates magma (molten rock) in the aesthenosphere. the aesthenosphere (70 ~ 250 km) is part of the mantle, the middle sphere of the earth that extends to 2900 km.

answer; /// the shaft of the hair consists of dead cells;