I have posted the below links before but the question of combining both of the results seems to be pertinent.. In the first link specialization of the musculature of the elephant's trunk leads to dominance of one side. In the second cooperation in society leads to one hand dominance in humans with the vast majority right handed. I feel my usual mode is to see the persona that I talk to residing in the right side of others. I communicate right side to right side and expect the feedback in the same direction. I am not so much as right handed as I perceive others are. It occurs to me that it is reason for the wide disparity in handedness as compared to the 50/50 chance with the lateralization of the elephants trunk. However once the process is started it stays in one side leads to greater dexterity and control.
Trunk to mouth
Martin is now beginning work on a project to determine whether these side preferences in elephants are learned from family members or determined primarily through genetics. Unlike humans, who are about 89 percent right-handed, elephants tend to be left- or right-trunked in equal measure. This suggests that elephant side preferences may be less genetically determined and possibly more plastic than human side preferences.
Shedding light on southpaws
Two Northwestern University researchers now report that a high degree of cooperation, not something odd or sinister, plays a key role in the rarity of left-handedness. They developed a mathematical model that shows the low percentage of lefties is a result of the balance between cooperation and competition in human evolution - See more at: