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 the jeans that you are wearing, but the jeans that carry your DNA, so to start I thought. We would talk very quickly about some things that you may have heard about your jeans that you might be wondering about. 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. I have also heard that there is less DNA in you in each of your cells than in those of a humble onion and that is also true and lastly, who among you has not heard it on television or read it on Facebook or in 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 other number of 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 it's very fashionable these days to attribute all sorts of phenomenal powers to our DNA, so the point at which you might start to wonder if there really is any reason to try to fight your genetic evidence is what What it does to you and me, that's the argument.

Innate is something you are born with, it is your DNA and you know some of you may find that comforting because if you are destined to gain weight no matter what, then you might as well enjoy lunch and stop feeling guilty about it. I know why to try to fight this. Everyone knows that you can't actually win against your DNA, but is it really true? You know your DNA is really so powerful and this is a question you may have asked yourself before and in fact it is a question you may have asked yourself. I've heard of it before because it has long been referred to as the

nature

versus

nurture

question.

Well, sometimes it is very true that there is nothing you can do about your DNA and let me give you a rather sobering example, rather than Huntington's disease. It is a terrible, 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 your mind and there is a cessation for which there is no treatment or cure, too. it is. 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 or all traits behave that way just because one of your parents he had cancer.

It doesn't mean that you two will necessarily get cancer even though you inherited half your DNA from that parent and the same is actually true with many traits like height and weight and even intelligence and also with complex diseases like diabetes or the heart. disease, 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 extremely unlikely that you will be as tall as them, so sometimes your life experiences Trump, your genes are nice and easy, sometimes parenting wins. and in fact, 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 mattered was

nurture

, the only thing that mattered was experience, nothing about humans was innate now.

Both positions are actually quite extreme. If you stop to think about it for a second, you'll realize that sometimes, when nature and nurture, when DNA and experience fight, the winner is really easy to predict, for example, you can wish for everything you want. you want for six. Fingers If you are not born with six fingers you will never have them. I'm really sorry to disappoint you, on the other hand, just because you can't speak German nowadays, there's nothing in your DNA that says you can't learn it if you don't start studying it tomorrow, so yes, sometimes the questions can be easy to answer , sometimes they are simple answers, but simple answers are really tempting or most of the time they are not correct and in fact complex problems are much more common and for me much more. interesting than simple ones, so I want to tell you a story about my doctoral work.

When I was a graduate student, I'm a human evolutionary geneticist and what that means is that I'm really interested in something that the fragments of our DNA make up. we humans and that and how they do it and when I was a graduate student I focused on this piece of DNA here and why this, well, it's clearly not very obvious from the sequence and in fact, the reason is something I don't know. you could expect everything because the reason is milk, that's what milk is, so milk is a really complex substance that contains all kinds of things, but the one that really interests me is this molecule called lactose.

Lactose is a sugar like glucose that your doctor tells you. and your parents and grandparents to be careful so that you do not get diabetes or like fructose that makes fruits taste sweet, but lactose is found almost exclusively in milk, when you drink milk, it goes down through the intestine to the stomach, where your body recognizes that it breaks it down and uses it to produce energy to feed itself and you may remember from school that our mammals, from seals to pigs and lions, all produce milk to feed their babies and, indeed, the young of sheep, baby gorillas, baby sea otters.

They all depend on their mothers to feed them milk at the beginning of their lives, but something happens to all these adorable animals when they grow up under your care and that is that they lose the ability to digest lactose and can no longer break it down, even kittens. So you can feed an adorable kitten a saucer of milk, he will, of course, drink it and lick it and probably be the happiest child you've ever seen, but if you feel like an adult self, a saucer of milk, he might drink it. . yes, in fact I can tell you that you will drink it, but believe me when I tell you that you are not digesting the lactose, you are not breaking it down.

I have cats at home, so believe me again when I tell you that I have seen and smelled and wiped away proof of the fact that they are not digesting lactose. The only exception to this are some, but this is extremely important, not all humans, so I am NOT a child. I hope you agree, although I can digest less. lactose very comfortably, but as we are in Singapore I feel very comfortable saying that the vast majority of you in this audience couldn't go home right now, drink half a liter of milk and not feel terrible for a while, that's all if I didn't they believe.

If you haven't done this experiment, please do, but don't just drink, you know, a sip of milk or a small capsule of yogurt. No no no. I want you to go home and have a nice drink. a glass of just nice, cold, lactose-filled milk, and I suppose you'll all end up pretty upset with me for convincing you to do that, but you know how I know? I mean, my job isn't really to go and ask animals how much they like milk and I don't know any of you so I don't really know if you like milk, but how come I feel so comfortable with my assumption?

Well, the answer is very simple, it is that simple. of the DNA that I showed you, in fact, is that bit that you see in red, something that I have that most of you do not have and that is because it comes mainly from people of European descent, you can see it here on this map which he took from some colleagues the new bunny telling his friends where that little sea is most common in places like Britain and northern Europe and where it is less common in the world, which is practically everywhere in blue, you can also see that is practically not seen. eastern India, which is the region I studied as a PhD student and which alone sees that small change that gives me the ability to digest lactose as an adult, so on the surface it would seem like a very clear case for let lactose or DNA win everything.

DNA beats nourish again, right, I mean just one difference and I can do something, you can't, you have them, so I have the mutation. I can digest lactose, you don't have it, you feel bad, it's closed, right, I mean purely, but actually let's take a step. because there is one thing missing in this story which is 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 we 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 is. it's actually not that powerful and let me give you another example, this one is a little more grim, but I think you'll see what I mean, so here in this figure you can see in this graph how common it was. American men are likely to die from different types of cancer at different times in the 20th century and I took this from a study by the Cleveland Clinic in the US. Then the statistics are for you. 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 right now, cancer is a disease that is fundamentally caused Because damage to your DNA damages 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 at the genetic fate of DNA, but in Actually that is really true because we all know that there is a recent cancer.

It has become 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 figure you will see that lung cancer was quite common. uncommon in the US until cigarettes became widespread and although 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 the lungs and that in turn dramatically increases the chances of getting cancer so what causes lung cancer is nature is DNA I mean if we damage DNA we get cancer maybe it's actually nurture I mean without smoking without damaging your genes there's no cancer so if you don't smoke you don't damage your genes you don't get cancer so maybe you see where I'm going with this because my question to you today is really well does this really have to be a fight?

Do we really need to think of this as nature versus nurture, nature or nurture? I think it's very clear that it's actually nature and nurture because the truth is, yes, you have genes, we all have genes and these genes do all kinds of things right, but if you look at a single gene, what it tends to do tends to be pretty. 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 between Yes, 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, they also respond to other things, they also respond to the environment in which you live, they respond to the The foods you eat respond to the decisions you make well.

It's actually very tempting to have a simple answer: have some yes or no nature or nurture. You may even want to blame someone in some situations. The truces. Life is pretty messy. That's not how life works. Life is really complicated. So next time you see. science, you see a newspaper headline that says Oh, scientists have discovered the cancer gene again. Please keep in mind that what that article really means is that scientists have discovered a cancer gene that is associated with perhaps a higher chance or even a lower chance of getting cancer. in a certain environment because the truth is that there is not a single gene for cancer, there are many genes, there are always many genes that control yes, 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, if you suffer from major depression at some point in your life, that's fine, but without the wrong environment, chances are all there will 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 no absolutely you are not the canvas on which they collaborate you are the product of their interactions