There's some good news and some bad according to this research [article in press] by Daniel Nettle:

[P]ersonality axes such as extraversion can usefully be seen as dimensions of trade-off of different fitness costs and benefits. It is hypothesized that increasing extraversion will be associated with increasing mating success, but at the cost of either increased physical risk or decreased parenting effort. In a sample of 545 British adults, extraversion was a strong predictor of lifetime number of sexual partners. Male extraverts were likely to have extra-pair matings, whilst female extraverts were likely to leave existing relationships for new ones. On the cost side, increasing extraversion increased the likelihood of hospitalization for accident or illness. There was no direct evidence of reduced parenting effort, but extravert women had an increased likelihood of exposing their children to step-parenting. The study demonstrates that extraversion has fitness costs as well as benefits. Population variation related in the trait is unlikely to be eliminated by selection due to its polygenic nature, likely spatiotemporal variability in the optimal value, and possible status- and frequency-dependent selection.

So, good-luck and have fun! But, be careful out there....

Addendum from Razib: GNXP readers might also find Henry Harpending & Pat Draper's 1982 paper, Father Absence and Reproductive Strategy: An Evolutionary Perspective (PDF), of interest. Harpending and Draper suggest that in low paternal investment societies sons tend to be more verbally than quantitatively oriented, while daughters tend to engage in sexual relations at an earlier age. For me, the most fascinating tidbit of information was this:

SAT scores of Harvard freshmen, 1964
Father absent: 668 math, 701 verbal
Father present: 716 math, 653 verbal

I suspect that verbal & mathematical skillsets might have some corelation to an extroversion/introversion range.