Neanderthals were right handed… Should we be surprised?

An article in science news this week puts forward the argument for population level Neanderthal right handedness based on stone tool scratch patterns on the front teeth of 500,000 and 30,000 year old Neanderthal remains. It’s a nice find but shouldn’t be all that surprising given the findings about ape handedness published earlier this month (see one of my earlier posts: If all extant African apes display population level right handedness (us included of course) then it is no surprise at all that one of our closest extinct cousins would as well. I don’t think I’m going out on much of a limb to suspect that the shared common ancestor of all extant African apes had at least a tendency toward right handedness, in fact this is what was implied in my previous post on the matter.


~ by confusedious on May 23, 2011.

2 Responses to “Neanderthals were right handed… Should we be surprised?”

  1. The real question is why? Brain development?

    • I think brain development was a part of it, but it is important to remember that there is evidence of handedness in all extant great apes which suggests that this tendency is quite ancient indeed. In the Homo line, our more definitive handedness most likely arose as a feedback between brain development and selection for those individuals best able to carry out newly devised tasks along with various other factors. Brains are biologically expensive and of course won’t become more complex in a vacuum. Most manual tasks only require increased dexterity in one hand, with one being the support hand or steadying hand and the other being the primary operator. It doesn’t make sense to evolve a lot of dexterity in both hands in this context, it is more efficient in terms of biological expenditure to develop monolaterally, thus handedness appears. It isn’t surprising to me that other primates show some handedness, all apes are quite manual creatures that manipulate things with their hands often and readily, their situation isn’t really that different from ours in that many tasks, at least I would suspect, are easier with a support hand and a dominant hand. In the case of a largely quadrapedal primate, the use of a single hand to manipulate an object also means that posture doesn’t need to be compromised, again more efficient.

      So to give some focus to my rambling mess here; the most parsimonious situation in terms of how evolution works is that handedness begins with our distant ancestors and how they manipulated objects in the most efficient manner available to them (quadrapeds not compromising their posture). This usually meant one handed manipulation, any indiviudual with a chance advantage in one hand over another had increased evolutionary fitness. Tasks that could be performed while sitting could be more complex of course, and would most likely favour the support hand/operator hand idea, again, any trait favouring this should in principle increase fitness. Increases in brain size, for whatever reason (mutation in regulation of brain size, nutrition, selection pressure for complex behaviour etc), allowed for the performance of new and more complex tasks. The greater rate of success in the performance of these tasks in those with slightly better monolateral manual dexterity, due to slight advantages in their motor control and possibly planning, were of greater evolutionary fitness. Add a heck of a lot of time and many generations and you begin to see amplification of the handedness trait and the neurological systems that generate it.

      I haven’t had much time to think this one through so there may be some gaping holes in what I have suggested. I’m working on logic here as I haven’t read any papers on this particular sequence of events. In my mind however this pathway involves as little teology as possible. When examining traits that we think define us, one way or another, scientists need to be very careful not to imply some insidious directional force in evolution.

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