from wikipedia: >It runs with the median nerve and supplies the same structures as that nerve. so, may be it affects dexterity (or ability to sustain it). Tha

from wikipedia: >It runs with the median nerve and supplies the same structures as that nerve. so, may be it affects dexterity (or ability to sustain it). That would be a huge boon in our industrial and post industrial society. May be it decreases load on the other 2 arteries and thus again improves some aspects of blood flow supply in the arms and/or to the palms. Also the dexterity seems to be a major factor in early brain development, kind of feedback loop. It may also just correlate with/manifest some overall characteristic (say "branch-ness") of the blood vessel system which say provides better blood flow to the body and/or brain. It also may be just a characteristic prevalent in some ethnicity or region, and the last 1-2 centuries there has been a lot of people moving/mixing, and if it is a dominant allele then it would explain such a fast spread.