the extra use of our thumbs in playing nintendo has driven the need for more blood flow to the digits.
It seems like those living in their parents' basement playing Nintendo would be less likely to pass on their genes. :-)
Maybe the medial artery helps raising the middle finger.
Considering even I still play video games, it is a useful mutation.
In the larger picture, more activities that require dexterous use of fingers (like typing, writing, machine controls) without using much other body motion. I question if this is so much and evolutionary change as a simple environmental adaptation activating a blood vessel that would otherwise atrophy from lack of need.