xia@cc.helsinki.fi (10/25/90)
In modern behavioural ecology papers, the following text is
often found after the explanation of the so-called Hamilton's
rule:
Therefore, a mutation that dictates its
carrier to sacrifice one unit of its fitness
for the increase of more than two units of
fitness of its full sibs, or of more than four
units of fitness of its half-sibs, will be
favoured by natural selection.
I think this is quite misleading. When an altruistic mutant
arises in a non-altruistic population, the genetic relatedness
of this altruistic mutant to its kins has nothing to do with the
inclusive fitness of this particular altruistic gene because
this mutated gene is not identical by descent to any other genes
in the population. So the gene suffers no matter how much
benefit the altruist can bring to its relatives. (Unless its
full sibs have a probability of 0.5 to mutate into an altruist
and half-sibs have a probability of 0.25 to mutate into an
altruist).joe@GENETICS.WASHINGTON.EDU (Joe Felsenstein) (10/26/90)
Xuhua Xia writes that: (statement of Hamilton's principle for kin selection deleted) > > I think this is quite misleading. When an altruistic mutant > arises in a non-altruistic population, the genetic relatedness > of this altruistic mutant to its kins has nothing to do with the > inclusive fitness of this particular altruistic gene because > this mutated gene is not identical by descent to any other genes > in the population. So the gene suffers no matter how much > benefit the altruist can bring to its relatives. After a few generations of reproduction the probability that the recipient towards whom the behavior is directed also contains a copy of that allele is 0.5 for sibs, 0.25 for half-sibs, etc. So Hamilton's principle works. Only in the unlikely case that the allele *always* causes the behavior and the behavior is *always* lethal is there any problem of the sort Xia suggests. ----- Joe Felsenstein, Dept. of Genetics, Univ. of Washington, Seattle, WA 98195 Internet/ARPANet: joe@genetics.washington.edu (IP No. 128.208.128.1) Bitnet/EARN: felsenst@uwalocke UUCP: ... uw-beaver!evolution.genetics!joe
T80SMS1%NIU@PUCC.PRINCETON.EDU (10/26/90)
xia writes: >I think this is quite misleading. When an altruistic mutant >arises in a non-altruistic population, the genetic relatedness >of this altruistic mutant to its kins has nothing to do with the >inclusive fitness of this particular altruistic gene because >this mutated gene is not identical by descent to any other genes >in the population. So the gene suffers no matter how much >benefit the altruist can bring to its relatives. Aha!! You have rediscovered the boundary conditions problem of group selection models. There was an extensive discussion of this (reams of papers) in the 70's dealing specificly with kin selection models. More generally, Wright's shifting balance models deal with this problem. See 2 papers by D. S. Wilson (Ann. Rev. Ecol. Syst. 14:159-187; Evolution 41:1059). The second in particular deals with conditions necessary for establishment of an altruistic allele. Sam Scheiner Northern Illinois University t80sms1@niu.bitnet