What if I told you that you didn't choose your best friend because of love, compassion, or some sort of cosmic linkage, but rather, because you both share a similar genetic makeup?
Researchers have identified two distinct patterns within social networks (the real kind, not the Facebook kind) at a genetic level when it came to the genes DRD2 (which has been linked to alcoholism) and CYP2A6 (which has been linked to character trait openness).
Basically, DRD2 carriers tend to make friends with other DRD2 carriers, and non-carriers befriend other non-carriers. In the case a carrier of CYP2A6, they tend to be the central hub in a group of non-carriers.
Basically, these guys are saying we don't pick our friends - science does. Interesting...