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← A misguided attack on kin selection

s.k.graham's Avatar Jump to comment 10 by s.k.graham

@ Comment 5 by vanghelie:

Can someone who understands this expand a bit and explain (to a layman) how kin selection explains the evolution of these traits?

vanghelie,

Ordinarily our genes get into the next generation by the fact that we reproduce. But if you are related to someone, then you will share some fraction (probabilisticly) of genes. So any gene, A, that you have has a r chance (or think 100 time r percent chance) of being in an individual with relatedness r (for examply normal diploid parents such as humans have relatedness 1/2 with their own offspring, siblings also have relatedness 1/2 -- in other words having more siblings is just as good as having offspring for reproducing your genes. If gene A in some way makes you sacrifice time/energy/resources so that you have less chance of producing offspring yourself, but you increase the chance of someone (or several someones) related to you having offspring, then the "loss" to gene A in not being pass on in your own offspring may be offset by the gain in its chances of being passed on in the offspring of your relatives. Hamiltons formula, rB>C captures this mathematically. For natural selection to favor a gene that causes you to make sacrifices for your kin, the cost to you, C my be less than the benefit to your kin times their relatedness (actually you might benefit muliple kin, so it should be sum(rB)>C where you are summing over all the kin who benefit from your sacrifice and r & B may be different for each individual kin).

The genes for soldiers jaws and honeypots can only have been passed on through queens that were related to the soldiers and honeypots. The were favored by natural selection because these traits in the workers helped the queen reproduce. The queen never has the soldier jaws or honeypot abdomen, so those traits did not directly help her reproduce, those traits only help her because they help her workers to help her. Her workers are her kin. Hence kin selection (reproductive success of the queen, who is kin to her workers) is the natural selection mechanism that favored the soldiers jaw and honeypots ant's abdomen.

Does that clear it up?

Tue, 31 Aug 2010 08:24:29 UTC | #508396