The battle between nature and nurture | Irene Gallego Romero | TEDxNTU

I'm here today to talk to you about jeans and when I say jeans I don't mean that I don't mean the jeans that they wear, but the jeans that carry their DNA, so for starters I thought we'd have a real quick chat about some things that you might have heard about. your jeans and you may be wondering first of all you may have heard that you share 99% of them with chimpanzees who are the closest living relatives and that is absolutely true you may have also heard that there is less DNA in each of your cells than in those of a humble onion and that is also true and finally, who among you has not heard on TV or read on Facebook or any other source? that scientists have discovered the gene for things like crime or maybe autism or cancer or beauty or attraction or really any number of other traits well i'm going to tell you something and that's something that's wrong and i'm going to tell you to say why so these days it's very, very fashionable to ascribe all sorts of phenomenal powers to our DNA, so the degree to which you might start to wonder if there's really any reason to try to fight your genetic evidence what makes you you and me is the innate storyline it's something you're born with is your DNA and you know some of you might find that comforting because if you're meant to gain weight no matter what then you might as well enjoy the lunch and stop feeling guilty about it, they know why try to fight this, they all know they can.

Actually, I beat your DNA, but it's really true that you know your DNA is really that powerful and this is a question that you may have asked yourself before and actually it's a question that you may have heard of before because It's been referred to for a long time as the

nature

vs.

nurture

issue, okay sometimes it's very true that there's nothing you can do against your DNA and let me give you a rather sobering example and instead of the disease of Huntington's is a terrible disease in which the cells in your brain slowly weaken and die, so you will quickly lose your ability to control both your body and mind and there is a cessation for which there is no treatment or cure.

It is also a completely genetic disease. all it takes is a single damaged copy of a single gene if you have that copy you will get the disease it is inevitable but not all diseases and not all traits actually behave that way just because one of your parents had cancer does not mean that you two will necessarily get cancer even though they inherited half their DNA from that parent and the same is true, in fact, for many traits like height and weight and even intelligence and also for complex diseases like diabetes or heart disease. heart, for example, you could be the child of the two tallest people in the world, but if you were malnourished as a baby, it is highly unlikely that you will be as tall as them, so sometimes your life experiences win out about your genes. nice and easy, sometimes

nurture

wins out and indeed if you look back fifty years, a hundred years ago, you will find that most philosophers flatly denied that

nature

had any role in the formation of humans, the only thing that What mattered was the upbringing, the only thing that mattered was the experience. nothing about humans was innate now both positions are pretty extreme if you stop to think about it for a second you will realize that sometimes when nature and nurture when DNA and experience

battle

the winner is very easy to predict For example, you can wish all you want for six fingers if you weren't born with six fingers you'll never have them I'm so sorry to disappoint you on the other hand just because you can't speak German today there's nothing in your DNA that says that you can't learn it if you start to study it tomorrow so yeah sometimes the questions can be easy to answer sometimes those are simple answers but simple answers are really tempting or most of the time its not right and in fact complex problems are much more common and to me much more interesting than the simple ones so I want to tell you a story about my PhD work so when I was a grad student I was a human evolutionary geneticist and what that means is I'm really interested in something what bits of our DNA make us human and how do they do it and when I was a grad student I focused on this bit of DNA here and why this well clearly not very obvious from the sequence and actually the reason is something you might not expect at all because the reason is the milk that's right milk so milk is a really complex substance that contains all sorts of things but the which really interests me. in this molecule called lactose lactose is a sugar like glucose that your doctor tells you and your parents and grandparents to watch out for so you don't get diabetes or like fructose that makes fruits taste sweet but lactose you have phone almo st exclusively in milk when you drink milk it makes its way through your intestine into your stomach where your body recognizes it and breaks it down and uses it to make energy for food and you might remember from school that our mammals from seals even pigs and lions. they all produce milk to feed their babies and indeed baby sheep, baby gorillas, baby sea otters all depend on their mothers to feed them milk early in life but something happens to all of these adorable animals when they grow up underneath from you and that is to say they lose the ability to digest lactose they can't break it down anymore even kittens so you can feed a lovely kitten a saucer of milk of course he will drink it and lick it and be the kid happier than you You've probably seen it before, but if you feel like an adult car, a plate of milk, you could drink it. i have cats at home so believe me again when i say i have seen and smelled and cleaned it proves the fact that they are not digesting lactose the only exception to this are some but this is extremely important not all humans so me I am NOT a child.

I hope you agree, although I can digest lactose very comfortably, but because we are in Singapore, I feel very comfortable saying that the vast majority of you in this audience could not go home right now, drink a pint of milk. and don't feel terrible for a while that's all if you don't believe me if you haven't done this experiment please do but don't just drink oh you know a little sip of milk or a little pod of yogurt no no no i want them to go They go home and pour themselves a nice tall glass of cold, good, lactose-filled milk, and I suppose they'll all end up pretty mad at me for convincing them to do that, but do you know how I know this?

I mean, my job is not really to go around. nd and ask the animals how much they like milk and I don't know any of you so I really don't know if you like milk but how how do I feel so comfortable with my assumption well the answer is very simple It's a little bit of the DNA that I showed you actually it's that little view, the one in red, it's something that I have that most of you don't and that's because it's mostly from people of European descent who can see here on this map that I took. from some mates, the new bunny tells his friends where that little sea is most common in popular places like Britain and Northern Europe and where it's least common in the world, which is pretty much anywhere in blue, you can too seeing that it's virtually invisible east of India, which is the region I studied as a PhD student, that I only see that a small change gives me the ability to digest lactose as an adult, so on the surface it would look like a very clear case for lactose or DNA winning all for DNA beating nurture again ri Well I mean single difference and I can do something you can't have so I have the mutation I can digest lactose not lactose you have, you feel sick, it's closed, right?

I mean purely, but really, let's take a step back because there's one thing that's missing from this story is the milk, where does the milk come from, you know that part is certainly not encoded by that little C, so the truth is that yes, I have a mutation in my DNA that allows me to digest lactose if I don't have access to cows, goats, sheep, camels or any other animal that we can milk, that mutation is totally useless being able to digest milk is a totally useless skill if you don't have access to milk so maybe dna isn't that powerful and let me give you another example this one is a bit bleaker but i think you'll see what i mean so here in this figure you can see on this graph you can see how common it was for american men to die from different types of cancer at different times in the 20th century and i took this from a cleveland clinic study in the usa so the stats are for you u.s.

Men, as you can see, for most of the 20th century, the most common form of cancer has been lung cancer, which is the one I'm pointing to with a big red arrow there right now, cancer is a disease that is caused fundamentally from damage to your DNA that impairs your body's abilities to control when and where your cells divide, so in a sense, cancer is caused by your DNA, so here we are again DNA genetic fate, but in reality that is really true because we all know that there is a recent cancer. it became so common in the last 50 60 70 years and it has nothing to do with DNA.

What I'm talking about, of course, is the rise in smoking. In fact, if you look at the number, you'll see that lung cancer was quite a lot. uncommon in the US until cigarettes became widespread and while not everyone who smokes will get lung cancer and not everyone who gets lung cancer is a smoker, the fact is that smoking dramatically damages the cells in your lungs and that in turn dramatically increases your chance of getting cancer so what causes lung cancer is it nature is it DNA i mean if we damage DNA we have cancer maybe it's actually nurture i mean without smoking without damaging your genes there is no cancer so if you don't smoke you don't damage your genes you don't get cancer so maybe see where I'm going with this because my question to you today is really okay this really has to be a fight do we really need to think of this as nature versus nurturing nature or nurturing me?

I think it's really very clear that it's actually nature and nurture because the truth is, yes, you do have genes, we all have genes, and these genes do all sorts of things right, but if you look at a single gene, what does it tend to do? It seems to be quite small a single gene could do something like make a protein that breaks down lactose and in isolation that's not really surprising you might tell yourself that's a fair criticism but the beauty of the system is that the genes respond to each other a gene can react to the product of another gene, but even more surprising is the fact that genes not only respond to each other, but also respond to other things, they respond to the environment in which you live, they respond to the foods you eat, they respond to the decisions you make well it's very very tempting to have a simple yes or no answer, nature or nurture, you might even want someone to blame in some situations, truces, life is pretty complicated, that's not how life works, life is really complicated, so the Next time you see science, you'll see a newspaper headline that says Oh, Scientists Have Discovered the Cancer Gene Again, keep in mind that what that article really means is that scientists have discovered the cancer gene.

Seeing a cancer gene that is associated with perhaps a greater or even less probability of getting cancer in a given setting because the truth is that there is not just one cancer gene there are many genes always many genes that do control your probability of getting cancer but also things like your height, your weight, the shape of your face, the color of your skin, even the slightest bit that you've suffered from major depression at some point in your life, that's fine, but without the wrong environment, probability and chances is all there will ever be, so I want to leave you with this final thought despite what you may have heard before.

You are not the

battle

field on which nature and nurture fight. No, no, absolutely not. You are the canvas on which they collaborate. You are the product of your interactions.