Antagonistic Pleiotropy (AP) is an evolutionary theory that explains why evolution does not weed out certain mutations that cause harm to an organism later in life. According to AP, these mutations provide other significant fitness advantages earlier in life, thus exerting positive selection pressure; the negative effects manifest after the organism has reproduced. The process of ageing/senescence is explained by this phenomenon.
Some other examples of AP in genetics are as follows.
- The mutation that makes one susceptible to sickle cell anemia provides resistance against malaria in early life. Therefore, in regions with high prevalence of malaria, this mutation is maintained in the population.
- The BRCA1 and BRCA2 mutations increase the risk of breast and ovarian cancer later in life, but are associated with increased fertility and reproductive success earlier in life.
- Some mutations linked to Alzhimer’s Disease and cardiovascular risks may provide early benefits such as resistance to childhood infections and enhanced cognitive function.
The example that comes to my mind immediately when thinking of AP is a boar or a goat with its tusks or horns so large that they dig into their eyes. These weapons warded off competitors early on, helping the animals succeed in breeding; later on, the weapons turned against the wielders.
References
- George Williams, Pleiotropy, Natural Selection, and the Evolution of Senescence (1957).