Question 041117c: What is Haldane's dilemma?
Answer 041117c: (from: ReMine, W.J. (1993): The Biotic Message. St.Paul
Science. Saint Paul, Minnesota, USA.)
"In the 1950s the evolutionary geneticist, J.B.S. Haldane,
calculated the maximum rate of genetic change due to differential
survival. He reluctantly concluded there is a serious problem here,
now known as Haldane's Dilemma. His calculations show that many species
of higher vertebrates could not plausibly evolve in the available time."
"Evolution requires the substitution of old prevalent traits
with new rare traits. There are limits to the rate these substitutions
can occur, limits that depend primarily on the reproductive capacity
of the species. Haldane's Dilemma examines these limits.
Imagine a breeding population of 100,000 individuals. Imagine
99,998 have the old trait O, and two (a male and a female) have the
new trait N. Imagine trait N has just arisen from O by beneficial mutation.
The evolutionary goal is to substitute trait N for trait O in the population.
To accomplish this goal, differential survival must eliminate the 99,998
type O individuals and all their heirs.
This can be accomplished in a single generation if there is
perfect selection. (That is, if the survival values of O and N are
0 and 1 respectively.) Yet, there is an enormous cost involved. For
every surviving type N individual there are 49,999 individuals (type
O) that must perish without heirs. The population must be regenerated
from the two survivors.
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