DRD4 and inter-racial mating

An allele in the DRD4 gene has previously been found to be associated with ADHD, novelty seeking behavior, migratory behavior, and exhibits marked population differences (Harpending and Cochran wrote an important paper called "In our genes" on this a few years ago in PNAS). People have also looked at its effect on reproductive behavior and personality in birds.
I'm surprised by what they did in the paper below. First they looked at timing of reproductive behavior. Then they looked at whether people with this 7R allele had more multiracial ancestries!! I did not look at what their reasoning for this was, but it probably goes something like this. Those with the 7R allele are more prone to novelty seeking and migratory behavior, therefore more likely to out-marry? It seems there would be several confounders here, but maybe they considered those. These results regarding multi-racial ancestry and the 7R allele are very surprising to me.

Polymorphisms in the dopamine D4 and D2 receptor genes and reproductive and sexual behaviors.

Eisenberg, D.T.A., Campbell, B., MacKillop, J., Modi, M., Dang, D., Lum, J.K., and Wilson, D.S. .

Evolutionary Psychology, (2007) 5(4): 696-715.

Abstract: Human reproductive and sexual behaviors are heritable and may represent
integral life history traits that are likely partially subserved by the dopamine system. Two
dopamine receptor polymorphisms, DRD4 48bp VNTR and DRD2 TaqI A, were examined
in relation to the Sexual-Orientation Inventory (SOI), age at first sexual intercourse, desired
age of marriage, and desired age to have children in 195 (45% male) individuals from a
general student population. As DRD4 7R alleles have been associated with migratory
behavior, we also examined whether those with more 7R alleles had a greater frequency of
multi-racial ancestries. Minor alleles of both polymorphisms (7R and A1 respectively) are
believed to decrease the function of their respective receptors. Individuals with DRD4 7R
alleles were more likely to have had sexual intercourse and to desire children earlier in life. In addition, DRD4 7R+ individuals were more likely to report multi-racial ancestries.Individuals with DRD2 A1 alleles were more likely to not want children and not want to marry. These results suggest that polymorphisms in the DRD4 and DRD2 genes are meaningfully associated with variation in reproductive and sexual behaviors. These results are provisionally interpreted as consistent with other findings suggesting that DRD4 7R and DRD2 A1 alleles are adaptive for lower offspring investment strategies in dynamic social environments.