is that if linkage disequilibrium is introduced by genetic drift, the two loci
should gradually come back into equilibrium at a rate determined by the amount
of crossing-over between the two locThe three possible causes of linkage disequilibrium
are selection on multilocus genotypes, population admixture, and genetic drift.
Selection was ruled out because one of the loci is selectively neutral, and
population admixture was ruled out because the 84GG allele is not known
to occur in other populations. However, it is possible that one of these two
causes might be a factor - there might be a third linked locus, as yet
unidentified that selection is acting on, or a now-vanished population might
have contributed the 84GG allele. However, if selection is not a factor,
the origin of 84GG can be calculated using the known rate of
crossing-over to estimate the rate of decay of linkage disequilibrium.