Transcript

Darwin's theory of evolution

Audio

You can also listen to the interview (MP3 15.46MB).

iTunes

Visit this channel at La Trobe on iTunesU.

Related podcasts

This podcast is part of the series Celebrating Charles Darwin. Please view related podcasts below:

Matt Smith:

Welcome to the La Trobe University podcast, I’ll be your host, Matt Smith. I'm here with Dr. Ben Kear of the Genetics Department to talk about, well not so much Darwin or… what do you know about Darwin, Ben?

Ben Kear:

Well, he had a problem with his lips.

Matt Smith:

He had a problem with his lips.

Ben Kear:

He had quite bad windburn and so I understand at some point he had a bit of a recurrent chronic problem: lip pain.

[Laughter]
Matt Smith:

So he got that from standing in front of the ship, probably.

Ben Kear:

Quite possibly. Or, alternatively, I just made that up, so…

Matt Smith:

OK. I might need to check that later on. So not so much to talk about Charles Darwin but to talk about his theories of evolution. So, Natural Selection. Where exactly do you start with a theory like that?

Ben Kear:

Well, you'd look out the window and everything that either crawls, walks, flies, swims or grows is basically a product of evolution, and natural selection. So I suppose I start by differentiating the two. Natural selection is the key process that kind of governs how one species, as you might say, transforms into another. Effectively, it just means that animals are adapting to their environment all the time. And certainly through chance mutation, individual animals survive relative to others of the same species, same kind.

And, effectively, the fact that they survive and can reproduce is natural selection. The environment is putting pressure on the organism. The organism is effectively using what it has in terms of its equipment to either survive or not. And if it survives, it reproduces, and it reproduces its particular sweep of character structures whatever, and that's passed on. And that is, effectively, given vast amounts of geological time, how certainly species can adapt and change to their environment and in response to their environment.

Matt Smith:

You've been studying it in the fossil record in Australia. What examples have you found there of natural selection at work?

Ben Kear:

The fossil record in Darwin's day and now was really the only way we can see a lot of these processes in action. The simple fact is and it's always been hailed as the missing links, is what we're looking for. We want to find one of these missing links. The most obvious one that comes to mind is Archaeopteryx.

Matt Smith:

Archaeopteryx, yeah.

Ben Kear:

Archaeopteryx is basically an animal that lived some 170 million years ago in what is now Germany. An animal that is part-dinosaur, part-bird, if you like. That's not, I suppose, strictly true in tone. It's not a chimera, but it has a certain range of features that are indicative of its dinosaur in ancestry and also indicative of its sort of bird descendants. For example, it has teeth like a dinosaur. It has a long, reptilian-like tail. But it has feathers.

Matt Smith:

And had claws as well, didn't it?

Ben Kear:

It basically seems to have been certainly capable of running around on the ground like any carnivorous dinosaur, and it's related to carnivorous dinosaurs, and maybe even climbing sort of small trees and things like that.

There are certainly arguments as to how well it might have flown, but what we can say is it has got all the structures that would certainly enable it to fly. Its feathers are not downy feathers. They're basically flight feathers. It has a wishbone: a classic feature of birds. And for a long time, the absence of wishbones in carnivorous dinosaurs was hailed as a fact that, well, obviously they're not related to birds because they don't have wishbones. Since then, no wishbones have been found in everything, including Tyrannosaurus. So we know that it was actually there.

And also since Archaeopteryx, which is found in the 19th century, we've since had a huge sort of rush of discoveries of very bird-like kind of these dinosaurs. There's not just one. There's a whole range of these things. Some seem to have been more ground-based and probably lived much like their carnivorous dinosaur sort of ancestors. Others were definitely very bird-like and probably flew. And there's also true sort of birds alongside these things.

So you have this whole sort of mishmash bizarre intermediary forms. It's not just a single one. You've got a whole radiation of these things. And so this leads to sort of reconstructions now of a lot of these sort of true dinosaurs, carnivorous dinosaurs with feathers.

Matt Smith:

Well, it's been a very recent development, that, hasn't it? It's maybe not so much a scientific way to watch our progress, but I like to compare "Jurassic Park 1" to "Jurassic Park 3". By the time the dinosaurs made it to "Jurassic Park 3" they were starting to have feathers a bit.

Ben Kear:

Well, this is it. It's basically what has been known in the scientific world for some time, is filtering through into popular vision of what dinosaurs are. They're not big scaly monsters sitting in a swamp. They're suddenly dynamic animals. Something like the classic Brontosaurus type of, you know, big sort of dinosaur people would say, "OK, it's a big lizard sitting in a swamp." No, these things are more like elephants. They're dryland animals. They're moving… They're the huge walking stomachs, basically. But these are dynamic animals that probably had metabolic systems much higher than we would give to an average lizard.

And they probably had much more dynamic behaviors to go with them. So, there's a whole range of possibilities that were quite likely to these organisms. Dinosaurs are just one example of what you might say natural selection or evolution. There's a whole range of early animals that seem to be a sort of first tetrapods. And tetrapods are basically everything that isn't a fish in terms of the vertebrate world.

Amphibians, reptiles, birds and us. What we're talking about here is the transition from life in the water to life on the land, that suddenly what was once a fish crawls out onto the bank as an amphibian. Well, there were some initial findings and there's an animal called Icthyostega, which was hailed as the intermediary form, the first sort of amphibian.

Again, since then the fossil record has turned up many more intermediaries. And a lot of these things are much more intermediate than Icthyostega was. To give you a vision of what Icthyostega looks like, it's basically a big salamander-like thing, 50, 60 centimeters long.

Since then there's a lot of these other things. There's an animal called a Canthosty. There's a whole range of them. But the interesting thing is it seems to… it didn't have these fish crawling out onto the bank. It seems that you had fish-like animals adapting to live on the bottom in rivers and streams and lakes and this sort of thing, and that's the birth of the tetrapod limb.

Ben Kear:

So, effectively walking on the bottom of the stream pre-adapts you, if you like, to walking on land. It's a very small step to basically move from that sort of bottom-living, bottom-walking habits into living on land. So the intermediary forms are showing also what the structures are all about. So another problem, say, with arguing for evolution is people are also, "So, OK, how does a wing evolve? How could something as fantastic and weird as a wing suddenly pop into being?" The answer is it doesn't.

There's a long line of stuff. Pre-adaptation is the key. The feather of a bird probably didn't evolve first for flight. The idea is it might've been a modified scale-like structure that helped to maintain body heat. It's basically insulation. And as the feathers, over time and by chance mutation, became, well, more complex, different structures evolved, you had basically all the equipment kind of there to do suddenly some, you know, a dinosaur jumps out of a tree and discovers it can fly.

Yeah. It's this sort of stuff, but it's the sort of a couple of environment, genetic and what we call 'phenotypic' which is basically what manifests from your sort of genome, if you like, your structural features, and the environment that, and effectively behavior as well is also adaptation to a certain degree. So all of this is part and parcel of what you would see as natural selection and survivorship and reproduction, and the whole thing is effectively working together as a unit.

Matt Smith:

Now, it is theoretically possible to start at the start of life and trace, say, to where we are. Moral lesson, the fossil record. What do you think…that there's been no missing link between humans and what came before us and Neolithic Man?

Ben Kear:

Oh, there's actually many. There's lots and lots of them.

Matt Smith:

But somewhere along there is a missing link still. Isn't there?

Ben Kear:

You have to imagine the fossil record is like a jigsaw puzzle. And that's the standard analogy, but it's a good one. You got a jigsaw puzzle and then you take all the pieces out and you sort of mix them all up.

Matt Smith:

I think a jigsaw puzzle from a second-hand shop would be a better…

Ben Kear:

And then you lose half the pieces. And the pieces you got, you cut them into little bits. And then you lose half of those as well. That's the fossil record. The chances of things being preserved are often so remote that it's amazing we have any trace at all. However, saying that, fossils are incredibly common. It's just finding the right ones.

So, this is part of what the beauty of sort of, if you like, Darwin's legacy of paleontology is what it's all about. You find these tantalizing traces and then we can start to rebuild the picture. It's using each one of these traces and fitting them together with those that got us to the point where we are now. And it's certainly testament that we've come as far as we have. It's testament to just how good the fossils are in terms of the more time you have to look for them, the more stuff you find, the better information you get.

And to use the Archaeopteryx analogy again, in the 19th century there was one specimen and they argued until they were blue in the face over it. Now we've got this whole range, this sort of diaspora of different kinds of animals all clearly pointing to the same picture. We have these intermediary forms. And see, you've got all these little bits and they're quite distantly related, but we can see even from these that we've got what is coming together as a family tree.

So, for example, with the human family tree, we might say, "OK, you've got us and we've got a gorilla. How does that work?" The fossils tell us there's a whole range of other things that go in between. There's all sorts of apes that are related to the gorilla, which are here now have ancestors and have fossils. But there's also things like Australian Pithecines, which is a name you might or might not have heard. Upright ape-like homonids. And homonids is a group that we belong to. And there's a whole range of things. Australian Pithecines, and our genus Homo has all sorts of different types: Homo erectus, Homo habilus. There's a whole range of these things which clearly show stages, if you like, of evolutionary development.

The fundamental thing here is that evolution doesn't work in sort of an advancement. We aren't necessarily better than they are or they were. We're just different.

And given environmental changes that have occurred between when they lived and when we first evolved, we just happen to do a little bit better. And that's really all it comes down to. An interesting example is a recent discovery of the hobbit. This is supposed to be a sort of evolutionary holdover, if you like. Something that dates back in its lineage to an earlier form. The fact that it survived into relatively recently, geologically speaking, just goes to show that it wasn't primitive. It just was able to survive given those suite of environmental circumstances.

Matt Smith:

It was well-adapted to where it was?

Ben Kear:

It was well-adapted to where it was. And it happened to survive. And that's basically no more advancement in a human being than there is in an amoeba. And in fact amoebas, if you take sheer numbers, are much more successful than we are.

So there's no progression, is what I'm trying to drive at. It's basically, animals simply adapt, and they either survive or they die. And that's in a nutshell what Natural Selection and what life is all about.

Matt Smith:

So given the changes that have already happened before us, it seems inevitable that humans are going to continue changing and evolving in some way, shape or form?

Ben Kear:

We are evolving right now. I mean, every time a child is born, it's genetically different to everybody else on the planet. That's evolution. That chance difference, that mutation that occurred as the parent egg and sperm mixed up their genetic material and the sort of the cauldron and it all came out with a new individual, that the mutations that occurred in there and the mixture that occurred there, is basically evolution. The features in that new individual may or may not allow it to survive given the changing environment. So, it's everything that is occurring now. Like I said, you look out the window, you're looking at evolution in action.

Matt Smith:

Is there any predictions that you think are going to happen? Some people seem to be getting taller. I'm noticing a lot less… innie belly buttons are not around much?

Ben Kear:

Ah, the old belly button. Well, I mean, I suppose looking at the features that we have, you can see all bits of evolutionary holdover. Wisdom teeth are a nice one. Wisdom teeth are basically a holdover to a larger set of gnashes. Some people don't have them, for example. Some people just don't have the tooth buds and they don't occur.

Ben Kear:

It's just simply an evolutionary change. The appendix. The appendix is a holdover of a larger digestive system that we seem to have just got rid of as we incorporated more protein into our diet over time.

Matt Smith:

But aren't we kind of interrupting evolution by, well, the people who have appendixes aren't dying? That's what we are putting on. Do you know what I'm trying to say here? We're still going to pass on the gene for appendixes because we're just removing them from people and those people are continuing to live. Wow, I'm going to get into trouble, if I suggest that we put down everyone is born with an appendix.

Ben Kear:

Well, without advocating euthanasia… No, effectively, the fact that it exists at all is interesting. But, obviously, the fact that the appendix is not detrimental to survival means it's persisting.

People can still survive to reproductive age, and they've reproduced children that have an appendix as well. So it's one of those traits that hold over. And upright stands, our pelvis isn't really well-adapted to do it. There's still problems. That's why a lot of people get backache.

Ben Kear:

There's all these little holdover features. But, given time, things will change. They may not change, but some other feature might develop. You might tell me how the third eye in the middle of your head, who knows? Effectively, the little bits of pieces, even within our own bodies, these very clear indicators, very clear evidence of natural selection and evolution in action.

Matt Smith:

What do you have to say to detractors of Evolution? To people who don't believe in it?

Ben Kear:

This comes down to the basic argument of science versus religion. In my opinion, there is no argument.

People who have a religious belief rely on faith. Faith requires you to disconnect the logic cable. And you believe in what you believe in. And that's great if it makes you a better person. Go for it. What science is is not a philosophy of religion. It's a philosophy, if you like, of looking at the world, of understanding how and why things work. It's not going to tell you that God exists. God has nothing to do with it. Science is about looking at and testing problems and understanding the truth of what we see around us.

So, in terms of detractors of Evolution, if you look at in a scientific way, you basically have to say, "We'll come up with evidence against it." That's what science is about. You present evidence and test the case. And to this stage, nobody has come up with a better idea that seems to have disproven it.

It certainly seems to be occurring. We have all the fossil evidence, we have all the structure evidence, all the genetic evidence to prove that at least something is there. It's working and we can see it.

In terms of scientific approach to things, you can argue with that. But, as a scientist, you have to say, "We only know what we know based on the evidence we have." And in the future, who can tell? But it's certainly seems to be the case at the moment. And as far as I can see, and in my opinion, evolution is basically in action around us, within us. And it's something we deal with everyday of our lives and it's been on this planet, shaping life since it began.

Matt Smith:

Dr Ben Kear, thank you for your time.

Ben Kear:

Thank you.