Instant Genius - How the history of all life on Earth is written in DNA, with Richard Dawkins

Episode Date: October 17, 2024

Since the discovery of the double helix by Francis Crick, James Watson and Rosalind Franklin in the 1950s, human knowledge of DNA and genetics has grown almost immeasurably. We now know that genes affect every aspect of our lives, from our appearance, our health and even our personality. But more than this, our genes are a living document of our evolutionary past, an ancient document that, if read properly, can reveal almost everything about how we came to be how we are. In this episode, we’re joined by the evolutionary biologist and multi-million selling author Richard Dawkins to speak about his latest book The Genetic Book of the Dead: A Darwinian Reverie. He tells us how different species of animals hit on the same evolutionary strategies despite being separated by multiple continents, how natural selection doesn’t necessarily always follow the perfect path and how a scientist of the future may one day be able to read the genetic code of any living animal like a book to uncover its entire evolutionary past. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Music just as the artist intended. Visit name audio.com to learn more. Hello and welcome to Instant Genius, a bite-sized masterclass in podcast form. Every Monday and Friday, you'll hear world-leading scientists and experts talking about the most fascinating ideas in science and technology today. I'm Jason Goodyear, commissioning editor at BBC Science Focus. Since the discovery of the double helix by Francis Crick, James Watson and Rosalind Franklin in the 1950s,

human knowledge of DNA and genetics has grown almost immeasurably. We now know that genes affect every aspect of our lives, from our appearance, our health, and even our personality. But more than this, our genes are a living document of our evolutionary past, an ancient book that if read properly can reveal almost everything about how we came to be, how we are. In this episode, we're joined by the evolutionary biologist and multi-million selling author Richard Dawkins to speak about his latest book, The Genetic Book of the Dead, a Darwinian reverie. He tells us how different species of animals

hit on the same evolutionary strategies despite being separated by multiple continents, how natural selection doesn't necessarily always follow the perfect path, and how a scientist of the future may one day be able to read the genetic code of any living animal, like a book to uncover its entire evolutionary past.

So Richard, welcome to the podcast. Thank you very much for joining us. Thank you very much. So today we're talking about your latest book, The Genetic Book of the Dead, a Darwinian reverie. So that has the sort of typically poetic title that we've come to expect from yourself. So first off, what's the premise of the book? Well, the opening words are something like, you are a book, a work of literature, and the you could refer to any animal or plant. So any animal or organism is a written

description which could be read by a zoologist or a biologist of the future as a description of the worlds in which its ancestors lived and therefore provided the natural selection pressure to make it what it is. So in the book you mentioned that animals are a sort of a model of their past. So what do you mean by that? Yes. Well, I begin with a picture of a desert lizard which has almost literally painted on its back, a picture of a desert, a picture of pebbles and sand. And this is a fairly common thing with camouflaged animals.

They have a really beautiful rendering of their ancestral environment written on their back. I say ancestral environment, because, of course, although it is their own environment with a bit of luck, it's the ancestral environment, set of ancestral environments, which actually has done the painting.

Now, my thesis is that that rendering of ancestral worlds cannot just be skin deep. It must run right the way through every bit of the animal, because every bit of the animal is just as vital to its ancestral survival. And it's just that the skin, the actual external surface of the animal, is the bit that we can see. And that impresses us with the power of natural selection. But the power of natural selection must work right. the way through every detail of the interior of the animal as well. So the camouflage idea that you're talking about there you refer to as paintings, but there's also a type of camouflage that you refer to as sculptures,

like these stick insects that look like sticks or other things. So what's going on there? Well, that's an interesting distinction. A painting only works when the animal is actually sitting on the background that it resembles. The sculpture works whatever background it's on. something like a stick insect or a stick caterpillar or a potto, a kind of bird that looks like a tree stump. It still looks like a tree stump even when it's not actually sitting on a tree. A stick caterpillar still looks like a stick even when it's not perched on a branch of a tree.

So the operational distinction between the painting and a sculpture is if you pick a painted animal off its natural environment and place it on a bit of paper, it's immediately very conspicuous and it's probably going to be eaten. But a sculpture is not because it still looks like a stick or whatever it is, even if you put it on a bit of paper. So let's talk about genes then. In the book you say genes make a guess about the future that's going to happen. So could you unpack that a little bit, please? Yes, the idea of genes making a guess is, of course, rather metaphorical language.

They don't literally make a guess. But every animal comes into the world equipped by its genes with the apparatus to survive in its ancestral environment. That amounts to a prediction that the environment of the future will not be too different from the environment of the past. Fortunately, the world is a conservative place, and therefore that prediction will normally be fulfilled. If it's not fulfilled, if that desert lizard, for example, finds itself on a golf green, then it's pretty soon to be picked off. The prediction will be violated in that case. So we're talking all about genes. So let's just get some terms out of the way then. So what's the difference between a gene, a genome, and the gene pool?

Right. A gene is one gene. A genome is a set of genes in an individual. Nijin Poole is a set of individuals in a population of individuals. So sticking with the idea of reading them like a book, you quite often return to this idea of a sort of genetic palimpsest. What do you mean by that? Yes, a palimpsest is a document which is overwritten. In the days before paper was readily available, parchment was rather scarce.

And so scribes tended to reuse the same parchment and they would either erase or partially erase what was written before and then write over the top of it. Well, the book that is the animal must be a palimpsest in the sense that it's a document about not just any one moment of the past, but lots of moments of the past, that's ancient ones, slightly more recent ones, more recent ones and so on. So it is a palimpsest of lots of different past environments.

So sort of sticking with that idea then, let's look at the intermediary stages. So a lot of proponents of so-called intelligent design will use the argument saying, well, how can you end up with something as complex as an eye? You know, what are the intermediate stages from going for just a photoreceptor to a fully formed functioning eye? Yes, this is a very common argument, the problem of intermediates, and the eye is a favourite example. Camouflage itself is another favourite example. flight is another one. Anybody can see that the perfection of, for example, an eye or a camouflaged

animal works very well. But what about the early stages? What about when the animal, let's take the stick caterpillar, which in its ancestral form, the ancestral stick caterpillar would not have looked very like a stick. It would have just been a long shape thing. Well, the selection pressure that gave rise to the evolution towards becoming a stick caterpillar or a stick insect would have been provided by predators that were not looking straight out the animal or perhaps in an imperfect light, perhaps at dusk, perhaps they only caught sight of the animal out of the corner of their eye. And under those circumstances, when the seeing conditions are bad, only a very crude resemblance would do the trick. And since there's their

gradient of gradually improving seeing conditions slightly better light, even better light still, not quite out of the corner of the eye but a bit more close to full frontal, that this gradient of improved seeing conditions provided the intermediate stages of selection. The same goes for the eye. What's the use of half an eye? What's the use of a quarter of an eye? What's the use of a tenth of an eye? Well a tenth of an eye is better than no eye at all. You can see the difference between night and day. You can be warned when a predator flies overhead because a great looming shadow flies overhead. So a tenth of an eye is better than no eye at all. A fifth of an eye is better

than a tenth of an eye. Half an eye is better than, you get the point. I mean, there's a continuous gradient of improving conditions. And the final perfection of the eye, the sort of eye that an eagle has, is provided when perfection is almost there. A slight, less perfect eye is a bit less likely to catch a mouse or wherever it is than an even more perfect eye. So again, we have a gradient, a gradual gradient of improved eyes. So another thing, sort of returning to this palimpsest idea, is we can sort of figure out that life came from the sea and went on to land and went back again and things like this. How do we go about researching that?

Well, fossils tell us something about the history of life, and we know that all life began in the sea, and we know that vertebrate life stayed in the sea to a large extent in the form of fish, but also came out of the sea to a large extent in the form of amphibians, reptiles, mammals, birds. And the fossil record is rather good in this. We know quite a lot from fossils, the fish that first emerged from the sea and became amphibians. We know quite a bit about how reptiles evolved and how birds evolved, how mammals evolved. And the fossil record tells us this. We also had to talk about to speculate, really, I suppose, about the conditions that led to those gradual emergencies from the sea to the land.

And there's been a lot of constructive speculation about that. Plants came out onto the land first, and that meant that there was a good food supply on the land. And so any fish that could come out of the sea onto the land had a ready-made food supply waiting for them. What's rather interesting is that quite a lot of the ones who came onto the land went back into the sea again. In extreme cases, whales and dugongs and manatees and less extreme cases, seals and sea lions, turtles and so on. One of the most dramatic examples the book describes is tortoises who represented a doubling back again. because tortoises are descended originally from fish in the water. Then their ancestors came out onto the land.

Then they went back into the sea in the form of sea turtles. And then they came back onto the land yet again, because modern tortoises, land tortoises, are actually descended from sea turtles, who in their turn had an earlier incarnation on the land and then an earlier one still in the water and form of fish. So what can we tell about these histories and the relationships between these animals by studying their genes? So you'll hear that manatees or dugongs are more closely related to some earthbound animals. Yes, manatees and dugongs are related to elephants and various other African animals.

The evidence available to Darwin was fossils and anatomy, comparative anatomy, looking at the skeletons, for example, And we still have that evidence, of course, but we also have a very, very rich additional source of evidence from the form of molecular sequencing of DNA and proteins. And this is a very, very rich source of information because DNA really is a form of documentary information. It really is letters in a four-letter alphabet. it and you can compare letter for letter the DNA sequence of any two animals you like and work out how close cousins they are and by implication by reasoning actually how far back their common ancestor was so we know that there was a group called afrothairs which included elephants and dugongs and manatees and ardux and hyraxes and all these are related to one another. We know this from molecular evidence as distinct from, for example,

Eden Tates which exist in South America and so on. So sort of sticking with this theme, how about the notion of convergent evolution? So I think that's really interesting. So what is that and what are some examples? Yes, well, the genetic book of the dead has a whole chapter on convergent evolution. Animals that start out from different parts of the animal kingdom and then converge on looking the same because they have a similar way of life. And one of my favorite examples is pill bugs, so-called pill bugs, which are woodlice, but also there are millipedes which have converged on the same way of life and look extremely similar.

There's a whole host of interesting convergences in the Australian marsupial corner because an accident of geography meant that when the ancient continent of Gondwana split apart, Australia got the marsupials. And so all the mammals in Australia, apart from bats who flew there, all the mammals in Australia are marsupials. And they radiated into a great range of different types which are convergent upon the mammals which we're familiar with in the old world. So we have marsupial rabbits and marsupial mice and marsupial moles and etc. And they look like moles and rabbits and mice because they have the same way of life. One of the most famous ones is sinus sinus the marsupial wolf.

He looks like a dog and behaves like a dog. And it is unfortunately extinct. Ambition comes in all shapes and sizes. At First Citizens Bank, we roll with your goals because we're built for what you're building. fit for your ambition for Citizens Bank. You said this place was steps from the water. We just haven't found the steps yet. How much did we save?

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like for example a giraffe's long neck or the antieters' incredibly long tongue? Where does that fit in? Well, these are specialised animals, antiters. There are various convergent antites actually. There are antitas in South America, which are perhaps the most specialist on eating ants, and they have enormously long tongues. The long tongue is convergently evolved in various other animals in the rest of the world, which also eat ants.

The giraffe, well, that has a vexedly long neck, presumably for cropping trees and reaching higher up, reaching leaves that couldn't be reached by any other animal. That gives rise to problems like blood pressure. How do you manage to get enough blood pressure to push the blood up to the brain? It must have arisen in an extreme case in the form of those dinosaurs which have even longer necks than the giraffe.

So these are specialist animals which have found a niche, found a way of life which no other animal can do, and it's a rich source of food if you wouldn't get it, but it raises problems. So you also talk about learned behaviours and behaviours in general. So one thing that I thought was very interesting that you mentioned is these shrimp that clean eels teeth. I mean, that that seems to be completely suicidal behavior. So what do we know about that? Well, again, the cleaner fish way of life is something that has convergently evolved.

It's quite a large number of small fish that live on coral reefs. What they do is they get their food by picking off parasites and dead scales from larger fish, including even, as you say, picking their teeth. There has to be a kind of pact between the cleaners, and the cleanees because it would be very easy for the fish that are being cleaned to eat the cleaner and they don't. And the patch has a kind of ritual aspect to it. The cleaners tend to have converged on a particular pattern, a particular stripy pattern,

and a particular dance which they do, which signals a signal, which says the signal, I'm a cleaner, you'll need me again, don't eat me and they don't. And very interestingly, the same habit has converged from shrimps. There are quite a number of shrimps which also do the cleaner habit. Again, convergently, lots of different shrimps have independently evolved this habit. So all over the reef, you have cleaner fish and cleaner shrimps, many different species of both, which have converged on this way of life. And each one has a particular, I've called them barber's shops,

a particular cleaning station. And the larger fish have even been seen queuing up to be cleaned at these cleaning stations. So how about another behaviour then, which is very odd and interesting, which is nest building, but the building of structures, you know, by insects, by birds. What do we know about that? Well, a large number of animals make artefacts. And there are nests, as you say, nests, bird nests are made of grass, and some of them made of mud. There are wasps that build nest out of mud and they're very, very useful things.

I mean, there are some that look like organ pipes. They're called the organ pipe wasp. The sort of parallel tubes in which they capture a prey. It might be a spider. It might be a grasshopper and they sting it. These wasps sting it and paralyze it with the sting. It doesn't die. It's merely paralyzed.

It's kept fresh. And then they lay eggs in it. put it in the nest, in the mud nest, and there the larvae of the waspatch out and feed on the still living body of the grasshopper or the spider. There are bower birds in Australia and New Guinea which build not nests but bowers, which are beautiful structures. They really are beautiful, which lure females, male birds, build these bowers. and these are a kind of external ornamentation. They're a bit like peacock's tails, which are also to lure females, to seduce females by their beauty. But the bower birds have exported the equivalent of a peacock's tail into the bower,

so they don't suffer from the handicap of having a great big extravagant tail like a peacock, which obviously must attract predators, just in the same way that it attracts females. the bower is not part of the bird, but it does the same job of attracting females. And some of the boughs are remarkable. They're decorated with coloured berries, flowers, even beer bottle tops, which take the fancy of the male bird who builds the bower and also take the fancy of the female bird who is seduced by them. So returning to this sort of palimcest metaphor,

So how about times when something's taken perhaps the wrong turn or not an ideal path? Yes, there are examples where a designer would never have made the mistake that, what is a mistake in a way. My favourite example is the laryngeal nerve, which you find in all vertebrates. In land vertebrates, in mammals, for example, the laryngeal nerve, the recurrent laryngeal nerve, it's one of the cranial nerve, so it starts in the brain. the end organ is the larynx, the voice box. But instead of going straight to the voice box, it goes right down the neck into the chest,

loops its way around a big blood vessel, a big artery in the chest, and goes straight back up to the larynx. Well, that's a detour, a functionless detour, a pointless detour. In the case of a giraffe, it's an extremely long detour. And I assisted in the dissection of a giraffe, which is unfortunately died in a zoom. and we saw the laryngeal nerve going straight past the larynx, and instead of branching off and innervating the larynx directly, follow it way, way down, many metres down into the chest

and then straight back up again. Well, that's a detour which no engineer would possibly have countenanced. And it arises because of history. In the fish ancestors of that giraffe and all mammals, the equivalent of that nerve went straight to its end. which is one of the gills. And when the neck started to lengthen, fish don't have a neck. So when the neck started to lengthen in the evolution of reptiles and mammals, the detour,

each slight extension of the detour was just the marginal cost was very slight compared with the major cost of jumping it over the aorta, jumping it over the artery. And so each marginal increment in the detour was too slight to bother with, so to speak, in more scientific terms, any individual who essayed the major embryological task of changing the course of it, so that it went straight to the larynx, would probably have died because the embryological upheaval would have been great compared with the slight marginal cost of increasing the length of the detour. There's a similar detour with respect to the sperm duck that carries sperm from the testes to the penis. in mammals. It makes a similar detour for a very similar reason. So how about the notion of what

used to be called junk DNA then? So what is that and what do we know about it? Well, junk DNA is a rather loose term. It's used for various things. One of the things it might be used for is so-called pseudogenes, which are genes that very evidently contain code, contain the capacity to code for protein, all genes that work code for something. And pseudogenes have the code there, but it's never actually read. So that's one type of gene which might be called as junk DNA. There are also repetitive lengths of DNA, which not only don't do anything, but couldn't do anything. They don't code for anything.

They just, they really are meaningless. You can't read the code of them because there's no code to be read, but nevertheless, they're there. So that's another category, which has been called. junk DNA. I don't like the term because I think from my point of view, the selfish gene point of view, any gene can be there simply because it's there because it's there because it's there. Natural Selection favours genes that exist because they exist, whether or not they actually take steps to exist. So I tend not to use the phrase junk DNA, but those are two types of DNA which are sometimes called junk DNA. So most people know that genes are passed on.

from parents to offspring. But one really interesting thing that you point out is that some animals' genes can affect the genes of other animals. You mentioned the male bird song and the swelling of the ovaries. Yes, well, this is my notion of the extended phenotype. It's experimentally shown that singing in canaries and the equivalent of the so-called bough-cru display in doves has a direct effect on female birds,

when male does do the balko at a female, this causes her ovaries to swell dramatically. Similarly, when male canaries sing at female canaries, the ovaries swell. So this is a direct effect of behavior of male on female hormone production. I see it as a direct effect of male genes. That's rather unusual, most people don't see it that way. The reason I see it that way is that clearly natural selection has favored this influence of the male song on the female hormone production. And it must be therefore a Darwinian adaptation and that can only come about by the selection of genes. Well, normally we think of genes as affecting the body in which they sit.

but my notion of the extended phenotype allows genes to affect something outside the body. The simplest example is artifacts like the nests we were talking about earlier, or bowerbirds nests, mud-dobbing wasps, organ pipe nests. These are clearly Darwinian adaptations, but they're not part of the body of the animal. They're made of mud or they're made of grass. Nevertheless, they must be produced by genes because genes have to be selected in order to produce them. Well, the next step from artifacts

are the other individuals, and that's where the canaries and the doves come in. Natural selection works on the genes of male doves and male canaries to affect genes that affect the bodies of, in this case, female, of the species, other individuals. So the idea is that the extended phenotypes,

it's my phrase the extended phenotype means genes that affect something, outside the body, which can even be the body of another individual. So in the book, sort of by way of summary, you often mention this idea of the theoretical scientist of the future. So say you were able to travel forwards, what would be a few of the sort of highlights that you'd like to see? Yes, she's like, I make her female, this soft, SOF, scientist of the future. I conjecture that she will be able to, when handed an animal that nobody's seen before or a new discovery, be able to read its genes and its body and say

what its way of life, and more importantly, its ancestors' way of life, read it like a book. Thank you for listening to this episode of Winston Genius, brought you from the team behind BBC Science Focus. That was Richard Dawkins. To discover more about the topics we've just discussed, check out his book, The Genetic Book of the Dead, a Darwinian reverie. The current issue of BBC Science Focus magazine is out now. Pick up a copy wherever you buy your favourite magazines or download us on your app store of choice. You can also find us online at sciencefocus.com.

This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analogue warmth. Alongside French acoustic specialist focal Name creates high-end audio systems combining innovation with craftsmanship, so you can listen to music, just as the artist intended. Discover more at name audio.com.