CCR4 mutation

[biraju patel]

Hello, I heard a mutation in the CCR4 gene is known to prevent the M 
tropic HIV from infecting individuals.  I also believe it was found 
that in European populations this mutation appears homozygously in approx 
1% of the population and approx 30% heterozygously.  So since, most 
likely, it hasn't been long enough for that specific human population to 
"adapt" to HIV, why is the mutation or "HIV resistant" allele common in 
that population?

							Bear