This is the best explanation I have heard so far.
Though there seem to be tons of theories as to genetics of left handedness, there does not seem to be an established set of theories as to why the majority of the population is right handed.
I found it interesting that Cecil’s column (link above) says that there is no dominant handedness in chimps.
If you’re writing in English, lefties have trouble with fountain pens. Fountain pen ownership and use are both key to joining the secret societies that rule the world!
Orangutans have preferential handedness. In David Attenborough’s Life of Mammals, he sat for a while with a female orangutan who was definitely left handed (using a saw, hammer, and nails the caretakers left out for her). Her son was right handed.
Right. I think I stated myself wrong in my post. I meant to say that Cecil’s column says that 50% of chimps are right handed and 50% left handed. That makes human handed more mysterious unless you consider the link to language as speculated by others in this thread.
I have difficulty believing in a communication-linked hypothesis to explain handedness. Lots of other animals show favoritism to a particular side, with no evidence of a communication mechanism to support it.
For example, grey whales overwhelmingly prefer to feed using their right-hand side of their mouths. I can’t think of any way this might relate to signaling.
That’s not the only example of handedness in the animal world, either.
Asymmetries show up all over in biology even in mostly symmetrical critters - why is the pancreas on most people’s left instead of their right? There’s a lot of potential explanations out there and I’m wary of jumping onto one without a lot of evidence behind it - a more powerful explanation might explain handedness across at least large groups of mammals - or even larger taxa.
If you’re a lefty like me, your palm tends to smudge the letters as you write from left to right. (that is if you’re using a cheap pen that is prone to smudging)
Righties on the other hand, since they are writing away from the point of origin, they don’t smudge.
Righties = 1
Lefties = 0
Gus
:rolleyes: So write in Arabic.
(or, for that matter, in any of a number of languages that are written right to left, not left to right)
Let’s get something quite straight before we continue to discuss this topic. It is a common misconception that a genetic difference is selected for because it confers some advantage over those without it, that is, it makes it easier for you to do something. This has nothing to do with evolution whatsoever (if it did, every life form on the planet would have evolved into the “perfect” shape, with the “perfect” traits for survival). What evolution does is work against those with genetic traits that put you at a disadvantage for producing grandchildren. Even then, evolution isn’t perfect, or else spina bifida would have been eliminated, for example.
Thus, when deciding if a particular genetic trait has some evolutionary reason for existing over another, one should look to see if there is some particular reproductive disadvantage to having the disfavored trait. In this vein, note that the researchers discovered that the gene they identified as influencing left-handedness also influenced the development of a psychiatric condition (schizophrenia). So one possible answer to the question is that people who had the genetic disposition for left-handedness tended to be less successful in producing grandchildren, NOT because of their left-handedness, but because of a related condition controlled by the same gene (or genes).
This makes some sense, too. There doesn’t seem to be any specific reason why a right-handed person would be more likely to have grandchildren than a left-handed person. Being left-handed doesn’t make it harder to survive, after all, nor does it directly affect procreation (thank goodness! the many left-handed people here are thinking 
). So one of two things likely would have to be true: either left-handedness is a recent deveolpment compared to right handedness, so it hasn’t spread as far in the population, or something is linked genetically to left-handedness that causes left-handers trouble with producing grandchildren.
I also think it’s related to tool using. Being ambidextrous would probably use brain capacity in a redundant manner so people evolved to be “handed”. And while it doesn’t matter if people are right-handed or left-handed, if there were a approximately equal mixture of both you would often run into situations where a tool was the wrong “hand” or where you had to keep a set of unneeded duplicate tools. So it makes sense that there was an evolutionary push to have most people tend to be the same hand.
Natural selection operates both for and against; it creates as well as culls.
More likely it as I mentioned above: a consequence of our developmental laterilization (which also accounts for the split in functions between left and right hemispheres of the brain). To the extent that handedness might be connected with communication, the left side of our brains is generally considered the “language” side; as this was emphasized in humans, it may have resulted in more and more right-handers, simply because the left brain hemisphere also controls the right side of the body. In any case, it is unlikely that handedness was selected for (or against) in and of itself.
I disagree, for the precise reason I stated. If evolution worked to maximize the best traits, everything would have fingers, brains that had evolved to tool-making, and Winnebagos in the side yard.
Or think of it this way: bacteria can have resistance to Triclosan. It gives them no competitive advantage at all, generally. If they had no resistance, then human use of the substance would be bad news for bacteria. If humans never start using it, having it does you no good as a bacterium; except maybe for bragging rights or something. So it isn’t that Triclosan resistance is a positive, except in comparison to those unfortunate bacteria who don’t have it, once we start using it. It didn’t give them anything to make them more likely to have second generation offspring.
Or think of it this way: Dinosaurs are extinct because they lacked something they needed at a certain point in time. It isn’t that evolution selected in favor of mammals; after all, there are still plenty of reptilian and avian species around. It’s just that the particular series of events that combined to wipe out the dinosaurs didn’t manage to wipe out the mammals so badly. BUT, a different set of events at that time might well have lead to you and I being direct descendants of T. Rex.
I thought the right brain was considered the abstract thinking side (connected with language, artistic expression, et al) and the left brain was the analytical side. Thus, the assumption is that lefties (such as myself, who are in their “right mind” :D) are more prone to creativity. I imagine this is a generalization, and I may be mistaken in my interpretation, but isn’t language and communication a right-brained activity?
Suffice to say I disagree quite strongly with your assessment. That selection acts as a creative force does not in any way imply that it acts to maximize or optimize. I believe you are conflating “creative” with “optimizing”.
Consider the opposite: if natural selection served only to eliminate disadvantageous variations, then what would be left would be the “average” and the “superior”. However, in such an environment, the “average” would then be inferior, and would subsequently be removed. All you are left with then, is “superior”; indeed, if natural selection did serve only to cull, populations would necessarily be optimized!
However, that’s not how the process works. Darwin’s formulation was pretty basic: in the competition for resources, some individuals will possess variations which will give them an edge – even if but a slight one – in procuring those resources. Those individuals will then have a slightly higher-than-average chance to reproduce, and thereby pass on those variations to the next generation (providing those variations are heritable). The other side is that those individuals who possess variations which hinder them in the competition for resources will be less likely to reporduce and pass on their variations. The result is that the population gradually shifts as those favorable alleles accumulate in the population, while the detrimental ones gradually become less frequent. Such is the process of adaptation. As the environment changes, what is considered advantageous or disadvantageous changes as well.
Novel traits are often built from co-opted, previously-neutral traits, or traits which previously served different functions.
To argue that natural selection can only cull is to argue that some other process must therefore be responsible for the evolution of novelties; since the history of life is filled with such novelties, one must therefore argue that natural selection is not, therefore, the primary mechanism which drives evolution.
In the absence of Tricoslan, the resistance trait is going to be selectively neutral. It’s frequency in the population will be largely determined by genetic drift.
In the presence of Tricoslan, however, those with resistance now have a considerable selective edge against those without. As I mentioned above, it’s all about the environment in which one finds oneself. Previously neutral or even detrimental traits can suddenly become advantageoues, and so on.
Different language functions are apparently partitioned out to different side of the brain. Per this Wikipedia article, for example:
and