Are GMOs harming my health?

How do seedless grapes reproduce? What causes serial womanisers? What's the fastest way to cool down a fire? Why does brewing tea for longer taste better?
06 July 2018
Presented by Chris Smith
Production by Chris Smith.


Bowl of fruit


How do seedless grapes reproduce? What causes serial womanisers? What's the fastest way to cool down a fire? Why does brewing tea for longer taste better? Why do gazelles all look the same? Can GMOs be harming my health? Plus, saving the Northern White Rhino...

Eusebius - A fascinating story is our first science story this week, before we take listeners' calls, particularly in South Africa where you know people are very passionate about this most endangered of mammals, the rhino. And it seems as if there's a breakthrough potentially for at least one species.

Chris - Well let's hope so, Eusebius. This is the northern white rhino. There are two subspecies, the northern and the southern white rhino. The southern white rhino is not currently endangered, but the northern white rhino is the most endangered animal on earth - mammal on earth - because there are just two alive, and they're both female. The last male surviving died a month or so ago; he was called Sudan, but he died of old age and had to be euthanised because he had complications and repeated infections and so on. So what scientists are trying to do is to use the power of modern genetic engineering and in vitro fertilisation, and a knowledge of how to do this in horses - because horses and rhinos have ancestry together, so what works in a horse works to a certain extent in a rhino - to see if we can produce, or come up with, a strategy to produce new northern white rhinos into the future. So the research is actually published in the journal Nature Communications. Thomas Hildebrandt, from Berlin, is the first author on this paper that describes how they do this. So what they've done is to lay the foundations with this first paper that could then turn into a strategy to do this in future. So they've taken stored sperm samples from northern male white rhinos, and, unfortunately, those sperm samples are quite poor quality. In other words, the sperms are not very motile and if you just mix them up with eggs they're not capable of fertilising those eggs directly with high efficiency. So what the scientists have done is they've taken eggs from southern white rhinos - which are relatively difficult to harvest in their own right: they've had to invent a new way of doing this, you go in through the rectum and you can see on ultrasound where the ovary is and you put this very long needle in, avoiding a huge artery which runs nearby, and you harvest eggs from the ovary - and they've been able to mix those eggs with the sperm from the male northern white rhino, actually, using a technique called ICSI, which stands for intracytoplasmic sperm injection. This is where you take the sperm and physically inject it into the egg to get the genetic material from both to mix, and that produced embryos, and the embryos they've got. So they've got embryos now from doing this in southern white rhinos. They've managed to make embryos from northern crossed with southern white rhinos and they've taken this to the stage of early embryos where they're beginning to form what we call the blastocyst, which is where it's beginning to form a ball, with a ball inside a ball and that ball inside the ball is the developing foetus. So what they're showing here is that they can do this, they can make these early embryos, and they can also collect stem cells from those early embryos, because one other strategy now will be to turn those stem cells into cells capable of producing sperms and eggs. So we may be able to then produce a supply of gametes that can then be used to make more of these rhinos and specifically northern white rhinos, and they could then be put into a surrogate rhino parent, whether that's a southern or a northern white rhino doesn’t matter. Hopefully it will be able to then nurture those babies and we can bring back from the brink this otherwise critically endangered animal...

Eusebius -  Wow, that is really really exciting prospects. Lisa, good morning to you.

Lisa - Good morning.

Eusebius - Good morning. What is your question for us?

Lisa - Hi, this is actually from my 7 year old son. We were wondering about seedless grapes and how they're able to reproduce if they don't have seeds.

Eusebius - Chris?

Chris - Hello Lisa. Well this is an excellent question because one thinks well how on earth did these things come into being. It's not just grapes that have this problem. Bananas are the same: bananas are all clones. And when a banana plant grows, actually what's happened is that the root of the banana plant has sent up a sucker from the root, or a cutting has been made. And so you have a plant which is made by cloning a parent plant. You can clone grape vines in the same way: you take a cutting from a parent vine and you can grow a new vine that way and you end up with a vine which is genetically identical to the thing you took the cutting from. Now the great advantage to that is that you can breed and select for strains of plants that naturally produce grapes that don't make pips or don't make big pips, which is how we get seedless grapes. The downside is that those grapes are all genetically identical. So if a disease comes along which knows how to attack that particular species of grape, it's going to unfortunately mean that all of the population are vulnerable, and this is what's happening with the banana. Those nice big yellow Cavendish bananas we're all fond of are at risk of fungal infection, and there's a disease called Panama disease which is threatening bananas. It's already wiped out one very nice variety called the Gros Michel. And so scientists are quite worried about how we surmount this problem, because if plants are just clones they're all susceptible. When plants have sex and exchange genes, that's how they create genetic diversity and that's how they breed resistance into their population. And if we're thwarting that we're potentially laying them open to a fungal attack or other microbial and other kinds of attack from other kinds of threats. So the answer is that you do it by cuttings, you clone them that way, but you are laying yourself open, potentially, to them succumbing to disease in the long run.

Eusebius - Thank you for your question, Lisa, much appreciated. Carmen, not sure whether your question is an hour early. Maybe it's for Dr Eve more than the Naked Scientist but go right ahead, you can try your luck.

Carmen - My question, I think is scientifically relevant and serious because I think there is a genetic or some kind of a clinical, you know, explanation for why serial ‘man-isers’ or womanizers exist in this world. If we could select them differently, you know, and know that this is someone you will settle down with, that would be great. Is there a scientific explanation for these people?

Eusebius - Okay let's see. Chris, serial cheating in human beings - can science help?

Chris - Well I think it can actually. And it sounds like a slightly sort of trivial question but it's a very important question and scientists have been looking at this, not just in humans, but they started actually in, theres a guy called Larry Young who's done this, who has been looking at voles, because there are species of voles, there's a small species called the prairie vole another one called the montane vole. And one of these vole species are monogamous. The other vole is the complete opposite. It will mate with anything, given half a chance. So scientists thought given this very very profound difference in behaviour, but these species are so closely related, this must be genetic because they show this characteristic. So, if we compare the genetics of the two animals then the differences must account for this difference in behaviour. So it should be possible to narrow in on this, and actually it turns out that there is a difference in one particular receptor, a chemical docking station in the brain for a chemical called arginine vasopressin, and this is used to do various jobs in the body, but in the brain, in a certain part of the brain, it seems to affect the mating behaviour of these animals. And the receptor is different in the animals that are monogamous compared to the animals that will mate with anything given half a chance. And then researchers said, well, given that that receptor which is clearly changing the way that nerve cells respond to this brain chemical is different in these voles, what happens if we look in humans, will we find the same sort of thing, because if you've got one mammal - we’re very closely related as mammals to these smaller animals - therefore the same nerve circuitry might be happening in us. So they have gone and done these experiments and there is some evidence to suggest that if you look at the arginine vasopressin receptor in humans who have a higher divorce rate or have a higher rate of marital disharmony and a higher rate of playing away from home, let’s say, you can find that more often than chance there is a change in that receptor in humans compared with people who are more reliable, let's say. So we think there is a genetic basis to some aspects of this behaviour. You have to be very careful in saying this causes this to happen because there are many factors that affect human, and influence, human behaviour and there are cultural reasons, social reasons and possibly these genetic reasons. But yes, there may be a genetic underpinning for why some people are more likely to stray than others.

Eusebius - Okay, there you have a comment! Bev, Good morning!

Bev - Good morning Chris. Could you please help follow an argument that we have in our house. Every night when the fire is burning and I want it to cool down quicker, I separate the coal so it gets more oxygen and therefore burns back more quickly. But my husband insists on scraping it all together so it generates more heat and burns up more quickly, which is the way that is going to get the fire to cool down faster.

Chris - Ok, Bev, really, how much is this worth to me? What is the argument worth?

Bev -  Every time we have an indoor fire, we have the same argument, and I’m hoping that splitting up those coals is going to be the correct solution.

Chris - Yeah tell me what you want me to say and I'll endorse it. Just kidding. The bottom line, chemically speaking, is what's happening in a fire: There is a chemical reaction happening when you've got wood or coals on the fire. The supply of fuel which in the case of, let's call it charcoal for the sake of argument, that charcoal is carbon, it's reacting with oxygen in the air and it's producing carbon dioxide, and that is a very stable gas and because it's a nice stable gas then the reaction wants to happen. So it gives out lots of heat. Now if you pack lots of things together in the fire you are restricting the flow of oxygen to the fuel and therefore you're slowing down the rate of reaction and the rate of reaction is proportional to how much heat comes out of the fire. Now the total energy the fire can release is going to be the same because the fuel is the same, there’s the same amount of fuel, but if you spread the fuel out, assuming it stays hot enough to keep on reacting and burning, the likelihood is the fuel is going to release all of that energy much more quickly, because you've given much more access to the fuel to the air where the oxygen is. If you push all of the fuel together you slow down the rate at which oxygen can access the fuel. Therefore the rate of the reaction and therefore the rate of heat production is going to be slower, but because the amount of fuel is the same the overall energy released in total when when the reaction is completed is going to be the same. So you're both sort of right. I would say though that the likelihood is that if you heap it all together there will be unburned fuel in there so less heat overall is probably going to be released. So therefore there'll be some fuel left over when the fire's gone out. So your husband might be sort of right on that basis.

Eusebius - Words you never want to hear, your husband must be right. Mishal good morning, what is your question?

Mishal - Yes. Good morning Eusebius, good morning Chris. I was always wondering why it was suggested to us that allowing a teabag to brew in a teapot results in a much tastier tea than to aggressively swirl the teabag much faster and get to that point at a quicker time. Is there necessarily a difference in taste allowing the teabag to brew in the teapot compared of trying to speed up the process myself and swirling the teabag around aggressively?

Chris - As a very very tea-enabled person, I love drinking tea. I'm very fond of tea, We get through gallons of the stuff in our office, and we've got a couple of young people from America who've joined us to work with us temporarily over the summer, and they were initially extremely bemused by the quantity of tea that's consumed in the Naked Scientists Office. I think they've bedded in quite well now, they've increased their bladder volume to learn to accommodate large gallons of tea. But when you make tea, what you're basically doing is you're mixing dried out leaves which have got chemicals in them, and you're mixing that with hot water and the heat permeabilises the leaf tissue, and it releases those chemicals into the water. Now some of those chemicals are bigger heavier molecules than others, and therefore what you're going to experience is that the longer you brew the tea, and the higher the temperature, the more of those big heavy molecules you're going to allow out of the leaf shreds that are the tea leaves. So if you just dangle the tea bag in the water in a cup, then probably because the volume of water in the cup is going to be lower than the volume of water in a teapot, the average temperature, probably, of the water's going to be a bit lower, and the temperature is going to drive more of these big molecules out if it's hotter. So therefore you might be making your tea at a lower temperature than is optimal if you just do bag in cup. Also the impatient among us tend to not leave the bag in the cup for very long. We just give it a good squeeze and then chuck it away. And as a result more of those tea molecules are not going to come out of the teabag possibly. If you put it in a teapot you've probably got higher average temperature you're probably going to wait a bit longer and you're going to give more of an opportunity for the full spectrum of flavour molecules, the big ones and the small ones, to come out of the tealeaves and into the liquid. So I'd say that probably you do get a superior cup of tea if you’re patient, and have a nice warm tea pot that you've pre warmed. Of course that's one of the rules making tea properly, you’re meant to warm the pot aren't you, and you've been patient enough for this to happen. Bag in cup is okay but I wouldn't say it gives you the superior cup of tea that you're clearly seeking.

Eusebius - Thank you Mishal for your question. Much appreciated. Andrew you've been waiting 20 minutes - what question have you got for us all - then we've lost him there. Oh let's see whether we have you back. Andrew can you hear me?

Andrew -Hello.

Eusebius -Go ahead. What is the question.

Andrew - Good morning Chris. Good morning to you. I just came back from the Kruger National Park, the game reserve. And I saw the animal kingdom, the chimpanzees, the gazelles, the lions. They are all the same, the same size: their noses are the same, their ears are the same, the insects are the same, the birds are the same. Same exact same thing. Now I'm sitting having my coffee in a shopping center and I see people passing by from 50 kilos to 250 kilos.Their noses are different, their ears are different - why are we so different from the animal kingdom? The theory that we are a hybrid, would this play a role? This is my question. Thank you very much.

Chris - Thanks Andrew. And you can hear Eusebius back there doing his Facebook in the background. Is that what you’re doing Eusebius? I can hear you doing Facebook or something while Andrew is talking, you’re typing away - You're doing your e-mails or something?

Eusebius - I want to see if you can answer him correctly with Wikipedia.

Chris - Well the bottom line, Andrew, is that actually although these animals do look all the same to you they are subtly different, and they can recognize each other, and they do look very different to each other. And it's only because we are not looking closely enough at them. And the interesting thing here there was a guy I interviewed in America, about 10 years ago, who has been studying the psychology of face recognition amongst humans. And people say, and it sounds prejudiced, but it’s not - People say, when I go to a foreign country everyone looks the same initially, and it's only later you then realize how people don't look the same. And in fact what happens, he thinks, this chap in America, is that we have in our brain in the region of our brain that recognizes faces, we have an average face stored. So what your brain does is it takes all of the faces you’ve ever seen a merges them altogether, together it makes an average face, and then, to store everybody's face, that would be a huge amount of information. So what it does is it subtracts the face you're looking at, your friend, or the person you just met, from the average and it stores the differences. So your brain recognizes people by the differences from the average. And as we get used to looking at a range of faces our average changes a little bit, and it's easier for us to extract those differences and make them memorable. And in the animal world, of course, we're not used to looking at lots of elephant faces or chimpanzee faces or gazelle faces. So as a result they do look very very similar to us initially, but if you were a gazelle or a bird or a chimp and you spent a lot of time looking almost exclusively at your own your model of of the average face would be very different, and therefore you would see these characteristic differences. Animals are very good at recognising each other. Many of them have excellent vision, especially birds, and they can they can find their partner in amongst thousands if they're a penguin. Other animals also don't just use visual features to find their friends and partners. They can smell them. They use other cues as well, and it's only us humans that think that we're the special ones - these other animals all have differences that we can that we can spot if we know what we're looking for - but they know what they're looking for because they're one of them.

Eusebius - Speaking of social media multitasking let's take one from twitter, Chris. Felicity says: Eubie please ask Dr Chris why, if evolution supposedly helps species to survive, the human race does not evolve to be better from a social point of view, instead of seeming to grow closer to annihilating ourselves than ever before - does science and evolutionary theory have anything to say about some of the social and political imprudence of human beings?

Chris - Well you could argue that actually we're doing pretty well, because there's about seven and a half billion people on earth and that's in the space of not very long. In the blink of an eye we've gone from there being very small numbers of humans on Earth, to a species that's at risk of actually destroying the planet because there's so many of us, and if we weren't doing something right, in other words promoting our species, then our species numbers wouldn't be climbing - so clearly were doing something right, we're not annihilating each other. But you're right that actually as we increase our numbers, as we apply pressure in different ways, we are going to have to adapt. But humans are, and humans just like every other thing on earth, are evolving all the time. Evolution is the mixing of your genetic hand that you've been given to play by your parents, with the environment in which you find yourself - that environment includes the food you eat, the water you drink, the area you live in, but also the social pressures you're under. And people for instance who are very good at getting on with other people very good at living in close proximity to lots of people, they're very they're very good at resolving conflict people with those sorts of genes, insomuch as genes can encourage you to have those behaviours, they're going to do better in an environment which is intensely social - Very large population numbers - than someone who is endowed with genes that make you work very well out in the wilderness on your own for example. So we're continuously refining our genetic stock over time and there is a continuous process of adaptation. But superimposed on that's going to be short term social factors, like people falling out over something trivial and then nuking each other.

Eusebius - Lungelua, Good morning . What is your question?

Lungelua - Good morning Chris and Eusebius, how are you?

Chris and Eusebius - We’re good thank you.

Lungelua - Oh good. I just wanted to find out what is a side effect of the GMOs that we consume in South Africa. Why I'm asking this, is because I've realized that when I travel to other African countries and I eat your grapes, your other vegetables and stuff I don't have any problems. But it's only here in South Africa that I have to be seriously picky about this, that I even saw now, it's like almost everything I put in my tummy, it just makes me react. So is there any side effect, is there any health scares that we should be aware of concerning GMO.

Eusebius - Ok, good question.

Chris - GMOs are genetically modified organisms. That's what GMO stands for. And this is where in certain circumstances plants have had genes added to them to endow them with additional characteristics. Those genes might be, for instance, an ability to fend off a pest, an ability to make a particular gene product that endows that plant with extra vitamins, that kind of thing. This is quite widespread, and some countries have embraced this more than others. The evidence is that there is no danger from doing this as far as we can tell for human health, because we now have the ability to scrutinise the things that we make and the changes that we make, to make sure that we're not changing other aspects of the physiology and biochemistry of these plants. So as far as we know, there shouldn't be a major impact on human health. There are - it's very important here to be cautious about causation: when something happens it's very easy to attach significance by coincidence, and we think ‘that must cause that’, but actually the two were just associated in time, so it's very very important to be cautious about how you draw these associations. So there is no evidence that you're eating something that's genetically modified, and the thing that's genetically modified is causing your symptom for example - there could be many other factors that are responsible for this. So I dont think theres any big evidence that theres theres a health scare because of GMOs, and in some countries they've been in use for 20 years. There are GMOs being being consumed routinely by the public. Doesn't mean it's good or bad, but what I’m saying is that people are aggressively monitoring this, and we're not seeing evidence on the scale of consumption that would bear out there being a health impact.

Eusebius - I we've got time for one last question. We've got two callers left, now I feel so guilty despite having given up on Catholicism. I want to share the burden with Chris - Chris randomly choose between the numbers three and four.

Chris - We'll have number four.

Eusebius - Ok we’ll have number four. John good morning to you. Hi John. What is your question?

[Question from John is, unfortunately, not intelligible owing to poor line quality...]

Eusebius - So, if only around 2% of the human population is homosexual, Chris, is there a scientific explanation for why any genetic propensity towards homosexuality has not been more successful?

Chris - Well we haven't. People look very hard to see if there are genes which appear to segregate with people's sexuality in the same way as they've looked really hard to find genes that cause right and left handedness. They haven't found any compelling genes that say if you have this particular form of this gene you are more likely to be homosexual, that association has not been found, and it may well be that, actually, it's more complicated than just a gene that causes this. It may well be that what happens is that perhaps environments in certain circumstances make a person more likely to change their sexuality or to be a homosexual versus non homosexual. We don't know. It may well be that as you're growing up perhaps certain hormonal triggers make you more likely to be willing to embrace one or the other, and that may shift your perspective. But we haven't found any kind of genetic cause for this, and, certainly, as this doesn't seem to be associated with a deleterious effect on the ability of the population to grow, because if it were we wouldn't have seven point five billion people on Earth, so I think it's one of those things that that hasn't actually got any kind of negative impact on the population; therefore the population hasn't selected out this apart from on social grounds, because in some countries of course it has been selected out, or at least it's been been made illegal or frowned upon, so people don't practice.

Eusebius -  well some of us get deleterious on the dancefloor, but it's not dangerous for the population, so you will deal with it. Thank you Chris!

Chris - I'll look forward to seeing that!


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