Reshaping your genetic destiny
If genes aren't the only factor in fitness, what other forces might be shaping who we are? Could we therefore control our genes? Quite possibly... Professor Tim Spector talks through the emerging field of epigenetics with Connie Orbach.
Tim - I thing genes are overrated and we have to remember that we have less genes than the worm. So clearly, it's what you do with you genes rather than the number and the type of the genes that are important, because we like to think we are a bit more sophisticated than the average worm. So my work has really shown that genes are overrated; there is no real such thing as genetic destiny and that we've evolved to be much more flexible than people think.
Connie - Overrated! That seems a little controversial. Any everyone says how similar identical twins are. I wanted to look a bit deeper into this so I thought I'd go to meet a pair that I know really well. Meet my nieces, Florrie, Mabel and their mum, Nimmy Orbach...
Nimmy - it turns out Mae Mae's got the same mummy as you so you've to share, you do. Is Mae Mae allowed a cuddle from mummy as well?
Florrie - No!
Nimmy - They are completely two separate people. Their reactions to, you know, a bump, bumping their head. A reaction to the food in the moment. They like completely different things, they make completely different choices. They often want the same thing as one another in the way that siblings do. You want what your brother's got, what your sister's got. They're definitely twins but they're definitely, definitely two separate people.
Connie - And that's amazing because really, at this age, they've spent absolutely every, almost every second of their life together.
Nimmy - Pretty much. I think they've been apart; there was one walk where they were taken separately on different walks and other than that they have literally been, you know, in the same house or, yes they're always together yet completely different. They were completely different from the moment they were born and lots of the things that we could see as differences between them at the beginning that we kind of didn't want to associate with them at the beginning, have stuck a bit. You know, the whining and the groaning and I won't tell you which one is more of a whiner than the other one in case she listens when she's older. But one whined more than the other and she still does a little bit. It's amazing that they can have had the same experience, the same upbringing, the same genetics, and be so completely, undeniably different. Can't you Florrie?
Connie - Okay. So it seems there is something in this, and much more than just my two year old nieces. Tim has actually spent the last 23 years studying 10,000 pairs of identical and non-identical twins.
Tim - The last five or six years, I've turned my attention to why identical twins can very often be different. When all of us look at identical twins we see amazing similarities but, when you scratch beneath the surface, we find that although there's a general tendency for things to go together. When there's a key event like heart disease or Type 1 diabetes, the chances are when one twin has it, the other one actually won't have it. So this goes against popular perception where they think, identical twins who are essentially clones with 100% of their genes identical in every cell of their body, end up having rather different lives. Not only diseases, but also more likely than not if one is gay, the other is more likely to be straight. If one has extreme political views, the other one may have different political views. So sometimes it looks like this part of our makeup makes us much more flexible than we'd have believed.
Connie - You're saying some really quite fundamental differences if we're talking about diseases, which we expect to be quite genetic but also beliefs. It's not just nature, it's not just nurture but there's something else going here. What is that?
Tim - I think another big player here is epigenetics. That is the way in which our genes are switched on and off by chemical signals, and these chemical signals vary in all of us and can be influenced themselves by genes, but also by our environments and by chance. And one of the projects we've been looking at for the last five years is what differences between identical twins for any of these traits can be explained by differences in how their genes are epigenetically altered. And it looks promising that some of these changes; the differences in identical twins can be explained by these epigenetic switches. We don't yet know they're totally causal or whether they're just passengers at the moment.
Connie - Can you maybe give me an example. Take me through what can happen throughout their life to end with very different consequences.
Tim - Often there was a story of a family trauma happened when they were young teenagers or kids, and they react differently to that trauma. If there was a divorce, one would take comfort eating, the other would become anorectic and you'd then get a chain reaction after that because the two of them would, in effect, alter their genes because of that and in a way would always be different after that point. Time after time, twin studies have shown that twins will react differently to the same environment, which is kind of weird, but it might be an evolutionary idea that to keep us more variable and keep us less predictable as a race and transfer, in a way, different genes on to the next group of people. So that our predictability is perhaps being linked to our survival and the way we've escaped predators, and it might explain some our quirkiness in the human race.
Connie - When you mentioned epigenetics, we're talking about lifestyle and life events influence being back on your genes. Is that something that you can pass on to the next generation?
Tim - You certainly can in animals. Laboratory animals have shown that, for example, anxious experiences or stress can be passed on to the next generation even if that generation wasn't stressed, and there's epidemiological evidence that you can pass on some of these experiences on to your grandchildren. But the data is great in humans, but I think there's an increasing awareness that this is a phenomenon that does occur in nature so that the offspring are perhaps better adapted to a different environment than the one the mother had, and what we don't yet know is how important this is humans.
Connie - So I guess Florrie and Mabel may only get more different as time goes on and they start to make their own life decisions. Maybe the saying's right and 'variety really is spice of life.'
Nimmy - Where's Mabel gone?
Connie - Where's Mabel gone?
Nimmy - Hey Florrie, where's Mabel gone?
Graihagh - So Connie you're here with me now. Your twin nieces are absolutely adorable by the way. And that's really quite a staggering thought that what I'm doing now might affect my genes enough that my kids might feel those effects also.
Connie - I know it really changes what you think about just general everyday decisions. You know so often you think, hey I can do whatever I want - I'm young - I can smoke some cigarettes, I can go out and drink but then when you actually think about what that might mean down the generations, maybe we're all going to just become really sensible and maybe a bit boring.
Graihagh - Do you really think it's going to change how you view things and how you do things? Perhaps you might encourage yourself to go on that run or not have that extra drink. I mean often it's so hard to envisualise something that's so far away and so far in the future. I mean for me anyway when I'm thinking about having children.
Connie - Yes. I mean that's definitely true. I think the situation we're in with climate change shows that as much as anything else. Maybe I say I'm going to be more responsible, but probably, no, probably it's not going to happen.