MICHAEL CORBALLIS: Yes make makes no difference and until about fifteen hundred AD there was as many scripts that went right to left as left to right but and that led some people to believe that there had been cultures that wrote with the left hand but as far as I know its completely untrue.

GEOFF BURCHFIELD: How about the the pervasiveness of ideas that left and right are associated with properties like good and evil fairly strong?

MICHAEL CORBALLIS: They are strong in all cultures I think and that's simply reflects the fact that all cultures have been right handed. So its been natural to place positive value on the right hand or the right side of the body and negative value on the left and you can find that in in virtually all cultures and all languages if it comes to that.

GEOFF BURCHFIELD: Can you give us some examples of the extent of these from I presume they range from Christianity for example?

MICHAEL CORBALLIS: Well there's supposed to be over a hundred references I think to the right being positive in the bible and a large number of references to the left being being negative. so certainly in Christian thought and one can find examples in in ancient Egypt or or ancient Greece or African cultures Maori culture.

GEOFF BURCHFIELD: Any explanation for why the right hand should be seen as so much better or more desirable than the left hand then?

MICHAEL CORBALLIS: Well simply because most people are right handed and the right hand is more dexterous, more skilled and preferred. And I think its simply an outcome of of the biology I mean you can reverse the arguments and people do but because ah these cultural things are so universal and because they apply to cultures that go back so far I think one has to give precedence to the biology and that the cultural values that are placed on left and right have come about probably simply because people have been and still are right handed. Makes it a bit rough and left handers of course and they've often been persecuted through history.

MICHAEL CORBALLIS: I think first of all, handedness is not in the hands. I mean there's no way to look at somebody's hands and decide whether they're left or right handed. So handedness is in the brain. So what handedness is telling us I think is that in most people it’s the left side of the brain that controls manual activity; controls what we do with our hands. And to some extent it controls it bilaterally, incidentally. So where you have left-sided brain damage you often get a condition called apraxia which effects both hands. Apraxia means that people are unable to follow simple commands to do things with their hands. So it looks like manual control is largely under the influence of the left side of the brain and so is language. And those are probably the two most obvious aspects of cerebral asymmetry, the fact that language is on the left side of the brain and some degree of manual control. In complementary fashion, the right side of the brain probably has more to do with spatial perceptions, spatial awareness, spatial attention, things that are spatial and things that are emotional. So there's some evidence that the right side of the brain is more sensitive to emotional expression and so forth.

GEOFF BURCHFIELD: Do you believe its just a coincidence that both language and the tendency to be strongly right handed happened to be controlled by the left side of the brain?

MICHAEL CORBALLIS: Well no I don't. I mean I think they're clearly related. Something like 98 percent of right handers have language controlled on on the left side and I think it would be very surprising if there were not a link there. My view is that language is very much dependent on the hands and especially in evolution. It’s not quite so clear now unless you go to Italy I suppose but people certainly gesture as they speak and I think as you probably know deaf people all over the world have developed their own sign languages based on the hands. So the hands are certainly capable of carrying language with all of the sophistication that language has. And I think it’s extremely likely that language evolved in early hominids in our early ancestors as a manual system not as a vocal one. And I think that could explain why the two are so closely linked.

GEOFF BURCHFIELD: You hear people talk about how there's a high proportion of left handers in this profession or that. Any truth in that?

MICHAEL CORBALLIS: Architecture is the one that comes to mind where surveys have been done they're they're the group that do seem to stand out with a slightly higher proportion of left handers. I think there's a possible genetic explanation for that which of course presupposes that handedness has a genetic component. But basically the idea is that left handers are really part of a sub- population, a recessive population if you like, in whom there is no genetic disposition to be either left handed or right handed. So that's why you get some people being ambidextrous. So if there's no genetic disposition to be either left or right handed, its a matter of chance.

Now there may be some advantage to that state of affairs particularly in spatial pursuits like architecture, or art or navigation or anything that involves the understanding of the space. So that may be possibly, be achieved at the expense of some degree of language ability. So there's kind of a balance here, a genetic balance. If you're strongly right handed and left cerebrally dominant you may have spatial problems but be fluent in language. So these are the kinds of people who get lost on the way to the forum I suppose. And at the other end of the scale people who are left handed belong to a group who are not strongly lateralised, and there may be spatial advantages. That's pretty conjectural I should say but I think it does explain why you sometimes find ah in architects or artists that they're left handed.

GEOFF BURCHFIELD: What kind of evidence would you point to, to suggest a connection between language and hands?

MICHAEL CORBALLIS: Well it’s very hard to find direct evidence in evolution of course because of all our predecessors have passed on. But I think simply from the evidence we have. I mean for example trying to teach language to chimpanzees it proved virtually impossible to get them to talk, because they simply don't have the appropriate vocal apparatus. But it was much easier, it is much easier to get chimpanzees to communicate with gesture. So chimpanzees and gorillas have been taught literally hundreds of signs that represents words and actions.

So presumably when the hominids diverged from the African apes about five million years ago they were much better equipped to develop communication systems based on the hands because there's already a good deal of voluntary control and sophistication in what they can do with their hands whereas vocally they were probably not capable of doing much more than grunting.

So I think if language evolved in the course of hominid evolution it almost certainly started with the hands. Secondly of course as I mentioned a moment ago even now humans can communicate very effectively just with the hands. And even if you prevent people from speaking and and try to get them to communicate they'll do it with the hands; and they'll even develop little grammatical aspects. So experiments like that have been done. And we do it all the time if we go to a country where we can’t speak the language what do we do? We use the hands. So gesturing is very natural. I think its always been part of language and I think it was the major part of language in early evolution, but it’s strictly conjecture. It’s difficult to get any proof.

GEOFF BURCHFIELD: If there is this strong connection between the tendency to be right handed and the development of language does this then mean that people who are left handed have the language centre shifted to the right side of the brain?

MICHAEL CORBALLIS: Do the left handers have their brains in backwards? No that's not true. Something like sixty or seventy percent of left handers also actually have language on the left, which sounds a bit sort of paradoxical. But I think it goes along with what I was explaining before that left handers probably belong to a sub-group who are not strongly lateralised. So they can have the language on the left or on the right. So in left handers you don't get the strong genetic disposition to have language and manual control in the left. So its more likely to be random.

GEOFF BURCHFIELD: Michael how well accepted is the idea that the reason behind strong right handed preference is associated with language and the asymmetry of the brain?

MICHAEL CORBALLIS: That it’s a genetic? I don't think it'll be accepted until somebody finds the gene. So really now it’s sort of a mathematical game. It’s true of that one can predict handedness to some extent from the handedness of one ís parents and one can fit genetic models that will explain that um but equally of course you might have been taught handedness by your by your parents. I think people have the strong sense that it’s biological, that you are born to be left handed or right handed. So I think probably most would would regard the genetic theory as plausible but unproven.

Twins are a problem, because with twins it’s almost distributed almost exactly as one would expect by chance, surprisingly. So you quite often get what are called mirror twins where they have opposite handedness. So twins are one of the real Achilles heels of the genetic theory of handedness I would say. But it does run in families. I mean there's really no question I think that people are more likely to be left handed if they've got close relatives who are also left handed. The incidence of left handedness in families by the way virtually never rises above about fifty percent and that is again support for the idea that what you're inheriting is not left handedness, but the absence of handedness so that handedness is then determined by chance.

GEOFF BURCHFIELD: You say handedness runs in families. Couldn't that be explained by children just observing parents?

MICHAEL CORBALLIS: Yes that's the alternative explanation. It doesn't feel like that some how but there are certainly people who've tried to build a case that it’s entirely a matter of learning. What we really need and we don't have surprisingly to my knowledge is good studies of adoption, where you can try to correlate the handedness either with the adoptive parents or with the natural parent. And that would be one way I think to clinch it. Where such studies have been done ah they have suggested that handedness follows the natural parents rather than the adopted parents but those studies are not particularly good. They don't control very well for example for the age of adoption and one doesn't quite know when this learning phase will occur and I think we need better data on it. It would be one way to go to try to clinch it.

GEOFF BURCHFIELD: I take it from what you've said so far you'd be inclined to to ah to lob for the to lobby for the genetic explanation then for why handedness appears where it does?

MICHAEL CORBALLIS: Yes I mean another reason for supposing it’s probably genetic is that all cultures even cultures that have been separated for fifty or sixty thousand years have been right handed. And it’s hard to believe that such diverse cultures across the base of the earth could all have this one thing in common - 90 percent right handedness, that was entirely dictated by learning or by observing or being influenced by the handedness of your parents. So the sheer constancy of it, the sheer universality of it and the fact that it seems to be very largely human, not observed in other apes, suggests that it’s biological and probably genetic.

GEOFF BURCHFIELD: Why do you think the subject of handedness triggers such strong responses in people, especially lefties?

MICHAEL CORBALLIS: Well perhaps partly because it’s seems to defy the outward anatomy of people. I mean you can’t tell by looking at people that they've got the same symmetry. So here’s this thing that emerges in behaviour but it’s not immediately apparent in the way people are built. So it almost perhaps has a magical quality. Here you've got two hands that look alike, two sides of the brain that look alike, and yet manifestly they do very different things and have very different talents. So I think that sort of element of mystery about handedness it’s not clear why it should be there even. I mean on the face of it you would think we might be better off to be ambidextrous, having the ability to do things equally with the two hands. But not so.

So something in evolution has created this assymetry and it’s done in a mysterious way. I think that's one of the reasons and I think it also sort of instinctively is trying to tell us that people are different from other apes. It’s almost like we cling to the straw that here’s an outward sign that that we are different and superior. And certainly handedness is associated with the things that we tend to think of as placing us above other animals - the manufacture of tools, skill with the hands and language. So the fact that it seems to be associated with those things may be another reason why we're fascinated with it. But I'm only guessing. You'll have to ask the other people in the office.

QUANTUM: Professor McManus, you believe that at the core of the whole right and left-handed debate is the fact that the brain is right and left handed in a way. It’s not symmetrical. Can you explain what you mean by that?

CHRIS McMANUS: Well the brain is symmetric in most animals as far as we can tell and that the two halves of the brain each controls the opposite of the body and there's exact equivalents between the two sides and it’s only in humans that one half of the brain has suddenly started doing something which is utterly different to the other half and that's basically language. So that I'm a right hander and as I sit talking here it’s the left half of my brain which is producing the language and for most of the audience who are listening who are right handed it’s the left half of their brain which is interpreting what I'm saying. So we're massively asymmetric, yeah.

QUANTUM: What about the left-handers among us? Are they any different “inside”?

CHRIS McMANUS: Well the fact that there are left handers suggests that although that what I've described is the normal way round its possible to be the other way around and the fact that they there's a more than a few of them about ten percent of the population are left handed suggests there must be some advantage in being left handed but at the moment we don't know what that is. But there's also a strong advantage in evolutionary terms in being right handed. That's what the vast majority of us are.

QUANTUM: Why is that?

CHRIS McMANUS: My suspicion is it’s because somehow having language and having an asymmetric brain and being right handed are deeply tied together. And we can suspect that from the fact that if we look at the fossil record then two million years ago, two to three million years ago, in the African rift valley at the same time we're beginning to find evidence of right handedness, we're finding the first stone tools. There's evidence that humans are communicating with each other through language and so on, and they've got asymmetric skulls. And so all of these things are coming together.

Worn bones reveal the handed-
ness of 500 year old skeletons

I suspect that what happened was that we were symmetric, something happened in evolution history, our brains became asymmetric we became right handed and we got language all in one go. And by gosh that was a winning combination. It was the language that really drove it, probably. Left handedness probably evolved at much later stage. And I suspect probably in the last hundred thousand years so probably we were all right handed lets say two million one million years ago and then in relatively recent history something else has happened which has meant that left handers can survive as well.

QUANTUM: Why do you think we developed asymmetry in our brains in the first place?

CHRIS McMANUS: Well I think first of all we probably developed asymmetry because it came along with a lot of other powerful things at the same time. And if we look at the evolutionary record, if we go back about two and a half million years ago in the African rift valley weíre finding for the first time evidence of humans with a large brain. They're walking up right, they're making stone tools; they're right handed stone tools as far as we can tell. There are subtle asymmetries in their brain which suggests that the left half is different to the right half and all the evidence suggests that they’re probably communicating through language. And so we've got a very powerful combination of things and it’s those things together which are are being selected for. And my suspicion is that the strongest of those is actually language. And it’s the fact that we've got a asymmetric brain which allows us to have language. and language is the thing which really distinguishes us from the animals. If you if you want one thing that means that humans have taken over this globe in comparison with all the other animals species its the fact that we can communicate. its the fact that I can sit here wobble my lips make some funny noises and you can actually get ideas in your Brian remotely its a real winner, compared with any other animal.

QUANTUM: But left handedness, when did that develop?

CHRIS McMANUS: My suspicion is that left handedness is a more recent phenomenon. First of all we know that left handers have been around roughly the same proportions as they are now nowadays - about ten percent or so probably... What, we know for at least five thousand years, we've got archaeological records and artistic records of people using their left hands and so on in modern proportions for about that long. And probably about ten to fifteen thousand years the archaeological records suggests there are left handers. We can’t tell much before that, but my suspicion is it’s probably within the last hundred thousand years that left handers have come about. So my reading is that is what happened was that most animals are fifty/fifty right handers left handers. Two million years ago all humans became right handed - that's one hundred percent of them and that had its advantages. And then about a hundred thousand years or so ago another mutation occurred which meant that left handedness could come into being and it must have had some advantage to it and left handers have stayed around since then. So they’re there not because they're an evolutionary throw back to a primitive state, but because they're recent mutation which additional advantages. Now what they are is anybody guess but there probably is some advantage to being left handed otherwise it wouldn't be there in the numbers it’s there.

QUANTUM: Your genetic model. Can it explain the relative proportions of right and left handers?

CHRIS McMANUS: Well we think basically there's a gene for right handedness which accounts for the fact that most people are right handed. And so most of us have a double dose of this right handed gene, and that makes us right handed and that's straight forward. But the other gene is not a left handedness gene in any simple sense. Instead is what we call a chance gene. And people who have a double dose of this chance gene do not end up as either right hand or left hand. They have a fifty fifty chance of being right or left handed. It’s as if a coin is being tossed and the brain will only go this way or that way. And it could be either way. There's no control there at all.

The other thing that we can explain quite nicely is the fact identical twins are not identical very often for their handedness. And this is always a mystery to people. Why is that i've got two identical twins. Ones right handed, ones left handed? Well the answer is that we expect that from this genetic model because if those identical twins have the same genes and that gene happens to be the chance genes then one twin tosses a coin and goes one way and the other twin can toss the coin in uterus and go the other way and when we do the mathematical calculations we get almost exactly the proportions we’d expect.

QUANTUM: What are the implications of all this for language?

CHRIS McMANUS: Well what seems to be happening in language is that if you read the text books you'll find that most people are right handed and most people have language in the left hemisphere. And that's true. And probably if you've got this double dose of the right handedness gene then indeed that's the pattern you have. And so the text book descriptions are applied to the people with the double right handedness gene. But if you've got that chance gene then its a fifty fifty chance whether you have right or left handedness, and it also is a fifty fifty chance whether language goes into your right or left hemisphere. But those two fifty fifty chances are independent. Two separate coins are being tossed if you like. And so for those people with that gene a quarter are right handed in language in the right hemisphere a quarter are right handed language in the left hemisphere and so on. So we get all possible combinations and so left handers then are more likely to have language in the right hemisphere than are right handers. And again when you work through the maths it comes out at almost exactly as the proportions we find.

QUANTUM: So it’s not entirely mythical then that left handers are more likely to have, say, reading difficulties?

CHRIS McMANUS: I think that's probably right. There, there's no doubt when you look at the statistics that left handers are somewhat over represented amongst people with some language ah problems. And dyslexia is the one that's always quoted but stuttering is another one that probably applies. You also find some effects on childhood autistic and other conditions where there seems to be an excess of left handers. It’s not a very strong effect. It must be said most left handers have no problems at all in learning to read or learning to talk or whatever. But a few do have problems and my suspicion is what's going on here is that as the chance gene makes some things go to right or left there are some combinations that work well and there are other combinations that don't work so well. And so if you just happen to get the things lined up in a good combination then everything goes fine. But if it happens to be a combination where information has to be continually shunting back and forwards between hemispheres then that slow and inefficient and they may have troubles with certain tasks.

QUANTUM: What do you say to those who say, oh, it’s got nothing to do with any genetics. It’s environmental entirely?

CHRIS McMANUS: I think the the first thing is they've got to show their data. There's very little evidence of any major environmental events that actually predict whether people are right or left handed and there's been lots of stories birth distress was the commonest one it was argued that left handers are that way because their brains were damaged at birth. I did a study with 16 thousand children. No evidence of that looking at obstetric records and looking at how the children turned out later in terms of right or left handed no link at all and lots of other studies like that. So that's the first thing.

Secondly people say oh well you're right handed because you're parents taught you to be right handed cause their right handed and that theory goes back to Plato. He said we're right handed because my nurse maid made us right handed. There's no evidence for it and if you really want the clincher for that if you take two right handed parents and look at their children then the children are more likely to be left handed if a grand parent is left handed than if a grand parent is not. But both parents are right handed in that case. Its the genes running through. Its nothing to do with what the parents are teaching.

Final one. If you really want some evidence that handedness is biological rather than environmental, nice study by Peter Hepper in Belfast who is looking at real time ultra sonic scanning of foetuses in utero. And he found that foetuses of course sit in the foetal position, their hands up like this, and they do what all babies do; they suck their thumbs and you can see them sucking their thumbs on the ultra, the dynamic ultra sound records and 90 percent of babies suck their right thumb. Ten percent of babies suck their left thumb. Now that's clearly not learned. Its not environmental or anything like that. So I think there's a lot of evidence here we're dealing with something that's inbuilt and its biological rather than something which is merely learned or social or due to environmental problems or whatever.

QUANTUM: Can you tell us about the claims made regarding the clan of the Kerrs?

CHRIS McMANUS The Kerrs and the Carrs, yes, this is I think one of the things we have to realise with left handedness is that left and right is one of the great symbolic distinctions. And anthropologists love these symbolic distinctions. Left, right, up, down, good, bad, hot, cold, cooked, raw, - all this sort of stuff. And left / right as a result gets tagged onto all sort of other things and it starts to have these symbolic associations. And people often feel that left and right... Left must be bad, right is good and so on.

And the Kerr and the Carr story somewhat follows that. And the story as it runs is that in Scotland in the 12th century or so there was a clan by the name of either Kerr or Carr and the story seems to vary. And this guy was left handed and because of that he had an advantage in fighting with the sword. And in particular he could fight better when he was going down spiral staircases that went one way rather than the other. He had a whole family of little Kerrs and Carrs all of whom were left handed and they defeated all their enemies and they built castles galore all of which had left handed spiral stair cases rather than right handed spiral staircases. And so that's the basic story.

And then there was a claim in the literature a while ago that if you look at modern Kerrs and Carrs then people with those surnames are still more likely to be left handed. And it was a classic example of how not to do science. The people put out a claim to this effect on the radio and in the newspapers and when the Kerrs and Carrs phoned in and wrote in, there were many more of the left handed than right handed. Now we didn't trust that because of course there's the possibility of bias was immense. So I got a student to do a survey where we he went through the London telephone directory. He found fifty Kerrs and twenty five Carrs and phoned them up and asked them about right and left handedness in their family. And he also found controls in the London telephone directory randomly selected. And when he did this there was no excess of left handedness amongst modern Kerrs and Carrs, at least living in London. So we don't believe this. We think the all the claims are just due to bias in the surveys. Now I think it is possible that there was one original Kerr or Carr in the past who was left handed but even if that were the truth the chance of him still, those genes still manifesting in all the descendants nowadays are minimal. So I think probably it’Ss a nice story but there's not much behind it.

The nice thing about the Kerr and Carr story is that is does make you wonder whether a left handed swordsman may actually be in an advantage over a right handed swordsman. Now we don't do much sword fighting nowadays oh but if you look at the modern equivalents of that things like com ah international tennis competitions and so on you find there's a massive excess of left handers. And you find the same in international boxing, in certain games like snooker and billiards and so on and I'm told in international fencing and so on. So why are left handers advantaged there.

And the answer seems to be an interesting one its a strategic one. And that's that normally if I'm a right hander, if I'm playing tennis against another right hander I have to read the way they work. And so when I put a shot I want to put it in a place where they won't be able to return it very easily. And after while by playing a lot of right handers I learn where are the difficult places on the court for a right hander where the easy places now what happens when I'm playing a left hander I suddenly can’t read their shots properly. I put it in one place and its an easy place to return it. But of course they can read me very easily. I'm a standard right hander. So when a left hander is playing right handers they’re at an advantage. Most of their opponents are right handed and they can read them properly. But when they’re left their opponents can’t read them and the result is that there's an advantage to being the unusual type in competitive sports. And that's probably why we have an excess of left handers and maybe why those left handed Kerr and Carr swordsmen did so well.

QUANTUM: If we find a gene for handedness do you think people will start to use that to select one way or another?

CHRIS McMANUS: I think knowing what somebody's genes were to do with right and left handedness could be very useful in understanding a lot of problems to do with mind, brain and behaviour. And I think if things like stuttering, dyslexia, autistism, schizophrenia and so on, a lot of these conditions seemed to be associated with problems of one sort or differences in the way the brain is organised on its right and left sides. And so knowing about the genes for that could well be very useful indeed in helping us to understand those conditions. Whether it does ever result in any therapy I think that will be a long way down the road but understanding always helps anything in general.

QUANTUM: In fact, how close are we to finding the actual gene?

CHRIS McMANUS: I think we're getting fairly close and it depends really if we know where to look the trouble is that the human geno is enormous and knowing where to find a gene is the most difficult bit and I think in the past we haven't had much idea where the handed gene might be. However, I think if we have an evolutionary model of where the handedness gene might have come from then that should direct us and genes don't come from nowhere. If there is a hand gene that makes us right handed in general then it had to come out of something else and the most likely thing is it came out of some other gene that already existed. And we all have the gene which makes our body asymmetric. Most of us have our heart on the left side because we carry a gene for that. There's a very small number of people that have a gene which makes their heart actually be have a fifty/fifty chance of being on the right or left side. And this behaves in the exactly the same way in a formal sense as the genes for handedness.

So my interpretation might be that the most likely place we got our gene which made us left handed and make our brain asymmetric is that we took a copy of the gene which made our heart asymmetric and that gene mutated. And then instead of making early cardiac tissue flip slightly to the left so that our heart went on that so make our heart on the left side, instead it made our brain flip slightly so it got different on the left to the right side. Now if that's true then if we can find the gene that makes our heart be on the left side, the genes that make our brains asymmetric are probably very very similar indeed. And one of the most exciting things that's come up in the last six months is that very recently the gene which makes them the heart of mice be on the left side has been found and its been sequenced. And my prediction therefore is that now once now we know that gene if we start searching through the geno for similar genes then weíll find something else in the human genome which we won't find in the mouse genome and that's going to be that gene that makes us right handed and left handed. So I think that could give us a fast track through to finding the gene for for handedness.