I saw a paper on the violence issue - I think the idea of the researchers was that where there is a lot of fighting, lefties have an advantage because the righthanders do not expect and have not devised defences against a leftie. The Border family Kerr was one which had a lot of lefties. I remember that one family built their spiral stairs the "wrong" way, so that they had the advantage in defence. The usual curve allowed defenders to use the right hand. It occurs to me that if the curve favours leftie defenders, it also favours rightie attackers.

It also seems likely that as the number of lefties rises with increased violence, the righties would learn to defend against leftie opponents, so there would be a limit to this situation. I am rather worried about the almost totally pacifist tribe with almost no lefties at all. I suppose it isn't impossible that random processes would lead to this situation, but I would like to know what happened to lefties that did occur.

If the hypothesis that righthandedness is inherited, but lefthandedness is not, it is going to be much easier for members of lefthanded families, with weak handedness, to learn to use either hand than for genetic righties, with a strong laterality.

Penny