Reply #21: Evolutionary Argument for Incest -- I'm playing devils advocate here [View All]

[German-Lefty]

Inbreeding causes an increase in expression of recessive genes. Crossbreeding causes decreases the chance that those genes will become active, but doesn't directly influence the amount of those genes in the gene pool.

Example: Take two twin towns in Germany, one with all the people blond/blue eyed and the other with people that have dark hair/eyes. For hundreds of years these people stuck to their own towns. Then one day someone built a road in between, and they started mixing.

If we mix the chromosomes randomly over a couple generations. You'll have 1/4 of the population blond, but 1/2 the population carrying the "blond gene". The amount of "blond gene" hasn't changed, but the amount of blonds has decreased.


Most genetic disorders are caused by recessive genes doubling up. Every now and then there may be good traits from this too.

Premise:I'm going to make a premise which I'm not 100% sure of: Evolution is still working to remove bad genetic material from the gene pool and encourage the good stuff. Even if few people are directly being removed from the gene pool, people with a bad hand may have fewer kids.

The problem with genetic diseases is that they affect too few people. If everyone carrying a single gene X would go blind. Gene X would quickly die out. The problem is that when only 1/1,000 people carry a recessive gene X only 1/1,000,000 go blind. So evolution gets few chances to get rid of the damn thing. On the flip side: if X is a good gene that gives you super intelligence, evolution will get few chances to promote this gene.

Conclusion: You're probably doing your children more harm then good by inbreeding, but you are helping the species improve the gene pool.