Scientifically heres another reason:
Incest can lead to more disease in offspring
The findings have important implications for endangered species, which may find
mating with relatives unavoidable if they have a small pool of potential mates, say the researchers from Cornell and Binghamton University.
Using a powerful technique of
genetic analysis to disentangle the family histories of hundreds of wild
crows, the researchers were surprised to find that nearly a quarter of newly hatched crows result from matings between mothers and sons or other such close family members as cousins, aunts, uncles, nephews and nieces.
While this level of inbreeding might be expected in small, isolated populations where birds have few mating options, the study revealed surprisingly high rates of familial matings in a large, open population of crows around the Ithaca, N.Y., study location.
"It's very rare to find inbreeding and incest in wild populations in birds," said Andrea Townsend, a graduate student in the Cornell Lab of Ornithology's Fuller
Evolutionary Biology Program and the paper's lead author. "But in some cases, it might be that people expect it won't happen, so they are not looking for it."
By measuring the overall survival rates of both normal and inbred crows, the researchers found that the inbred crows often died in the nest prior to fledging, and those that did fly off were far more susceptible to such diseases as avian pox and bacterial infections.
Extracted from:
taboo in incest - Hanapin sa Google