BOL

Analysis of the genomes of >350,000 individuals revealed the existence of a small though measureable association between genome-wide homozygosity and some vital complex traits...

Directional dominance is predicted for traits under directional evolutionary selection, this study provides evidence that increased stature and cognitive function have been positively selected in human evolution, whereas many important risk factors for late-onset complex diseases may not have been.

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14618.html