My subject is the future of life on Earth. This is a very large and complex topic. It’s the subject of futurology. And in fact, I am a palaeontologist, I study dinosaurs, and you might wonder why a palaeontologist would have something to say about the future. However, there are some shared aspects which I will talk about, and this can provide some evidence to help us in making decisions. I’m a palaeontologist, as I say. I decided on this career when I was seven years old. I loved dinosaurs at the age of seven, and I think these days, young people still do. And I haven’t changed my view since. I love the job, teaching students, going to exotic parts of the world to dig up dinosaurs, finding new facts about the history of life. However, this kind of subject, studying the past, like studying the future, could be said by some not to be truly scientific. And I want to explore that a little bit first, how do we do this, before we get to the point of beginning to establish some facts and figures about life and current threats.
And this has been criticised by other scientists. For example, 100 years ago, Sir Ernest Rutherford, a very famous physicist, Nobel Prize winner, said, ‘All of science is physics, and the rest is stamp collecting.’ By which he meant that if you cannot make it into mathematics or physics, it doesn’t count. That excludes then the natural sciences, medicine and a lot of other areas. And I think at the far end of the spectrum would be my subject, palaeontology. I’d like to give you an example though, to show you how we apply scientific methods to achieve a certain level of understanding and certainty. And this is something that has been developing during my career so that when I started, a lot of what we did would be called a speculation or guesswork, whereas now, a lot of what we do can be tested and can be called scientific. The example I’m going to take is the question I asked when I was seven, ‘Could T.
rex bite a car in half?’ This is a question about the most famous dinosaur, Tyrannosaurus Rex, which was huge, five tons in weight, enormous jaws and teeth. Could it bite a car in half? Well, there were no cars in the Cretaceous, but let’s forget that for the moment. When I started, you could only answer that question by guesswork, or you could make some very simple models of the skull, like levers, and try to calculate things. If you were going to make a realistic model that had all the properties of the original bone and flesh of the dinosaur, you could not do it. But now, with the power of computing, we can do this kind of thing. So the way you calculate the bite force of T. rex, and the way people have done it, is they scan a skull and make a three-dimensional, digital model inside the computer. You then divide that model into a mesh, or into a framework of elements or small components.
And each of these elements can be given physical properties so that we know the physical properties of bone of living animals. These are material properties, like how far can you twist the bone before it breaks, how much compression can that bone take. And so all of those properties are mapped into the skull. And then you apply imaginary forces and increase those pressures until the thing breaks. And so the bite force of T. rex is huge. Let me lead you to the figure. Our bite force is about 800 newtons at most. The biggest bite force of any living animal is the great white shark, and that is about 5,000 newtons. T. rex, 50,000 newtons, ten times. And that’s equivalent to five tons of weight, acting. So it could bite a car in half. Why do we believe this method? Because this method is a standard in design and architecture. Finite element analysis is used for designing buildings like this one. You don’t simply build it and hope it doesn’t fall down.
The thing is designed in a computer, it is stress-tested using this program we apply to the dinosaur. I think we can believe it. But let’s move on. That was just a brief word about how you can actually apply science, I would argue, to questions that are not happening at our time, in the past, or maybe in the future. And in palaeontology, we don’t just find fossils. We also care about evolution and diversification, how groups have become diverse, how groups go extinct. And at the moment, we are crucially concerned about extinction. So let’s have a look at that, let’s explore that. What are the current views? And these views are expressed not by scientists, but also by very important politicians. So some of you may recall, a number of years ago, Al Gore, who was then vice president of the United States - He quoted a figure of 100 species are going extinct every day. So this is a very high rate of extinction, 100 per day, which is equivalent to 40,000 per year.
At the other end, other politicians, perhaps in President Trump’s camp, would say, ‘Don’t worry about it. Extinction happens. Look at the dinosaurs. We’ve got nothing to do.’So how do you connect between these two positions because of course we have to think about these points. The first approach that we use is to look at history. We have recent history recorded of extinction. So many of you will be familiar with the extinct bird called the dodo. This lived on the island of Mauritius in the Indian Ocean. The dodo was a kind of fat, flightless bird related to pigeons, and a very famous image of the dodo was in the famous children’s book ‘Alice in Wonderland’, where the dodo, who is a wise, old gentleman with a walking stick organises Alice and all the animals and says to them, ‘We will have a Caucus race.’ And a Caucus race is one where people start when they like and they finish when they like, and everybody gets a prize. So that was very nice, but unfortunately the dodo in real life didn’t get a prize.
Because some of you may know the first records of dodos were in 1598 when seamen reported they had seen this bird. They could go on the island and catch it very easily and eat it. And within 60 years it was extinct. Another example of recorded extinction is the great auk. This was a large bird that lived in the North Atlantic, and the great auk went extinct in 1844. How do we know that? Because collectors sent by a museum shot the last example. They were concerned that their museum did not have a stuffed specimen of this bird. They heard it was going extinct, so they thought, ‘We’d better get one before it dies out.’ So these are two examples of data about extinction. And indeed through the last 500 years, mankind has killed many species which are recorded like that. And this is the basis of the figure that Al Gore gave. Let me explain it. He gave that figure of 100 species per day going extinct. This was based on the bird data.
But we know something like 100 or two or three hundred species of birds have been killed by human activity in the last 500 years. And the figures are debated. It’s something like from half a species to four species each year on average. We don’t know for sure because of course people didn’t record everything. Now, how do we scale this up to get a global figure, from birds on the one hand to all of life? And the way it was done was simply to say, ‘We know how many species or birds there are alive today.’ There are 10,000, and the initial estimate for the diversity of all of life were 100 million. So you scale from four a day upwards, and that brings you up to this figure of 100 per day by multiplying up many times; 40,000 lost per year, 100 per day, based on that extreme high bird figure. At the other end, the lowest estimate is something like one species per day. This is because we are not sure about that bird figure, so we could take a lower estimate, and also we are actually not sure about the diversity of life today either. Some of you will know that you might think we would have named every species, we would know that - we don’t.
You can look at Wikipedia. There are thousands and thousands of pages describing all the living species, but there are so many living species that we have never discovered, never described, aren’t there in Wikipedia. So there is that uncertainty. One hundred million? Ten million? We don’t know. Those are the estimates of numbers of species going extinct each day. One per day, one hundred per day. Do we worry about that? This is where palaeontology comes in first, because fossil data allows us to calculate what would be the normal rate of extinction. Species do go extinct, so this politician over here was quite right. But was Al Gore right? We don’t know. You know, he was giving that high figure - maybe somewhere in between. But what is the norm? Is one a day okay? It doesn’t sound too many. If there are millions and millions of species, it is far too high. We know that the average duration of a species is two million years. They originate, they go extinct. Two million years.
And that means, as they come and go, on average, we would expect the extinction of five million species every million years, which is five species per year. So that does contrast remarkably even at the lowest estimate of human impact - 500 species per year is 100 times the normal rate of 5 per year. And at the bottom there is the dodo, just in case you weren’t sure what it looked like. So I want to look at two other topics briefly. One is risk. And so, one of the questions we would have estimating the total numbers is one thing. We have learned that we are impacting life harder than we should be. Human activity is causing extinction. What about risk? It’s easy to say of course, the dodo was stupid, it lived on one island, it just stood around and allowed itself to be hit on the head. To an extent. We worry about elephants, we worry about pandas, we worry about many individual species. Many of those have high-risk factors. So for example, an elephant is very large.
This means they need a lot of food, they need a lot of territory to walk around. And so it’s much harder to keep a sufficiently large population of elephants breeding and successfully in the wild. We don’t need to worry about rats, for example. They’re small and there’s lots of them. So body size is one risk factor. Being big is not a good thing if you want to survive as a species. What about the panda? They’re not so huge. They’re about human size. They have a specialised diet. They have evolved into a crazy position. As you know, they are eating bamboo without the real ability to consume it properly. If that food supply disappears, they’re stuck. So, secondly, restricted diet is a problem. The third one is shown by the dodo. If you live in only a very small geographic area rather than over the whole world, you are at risk. So there are three things to be: medium-sized or small, if you want to survive; broad diet, willing to eat everything; and living over the whole world.
So that includes human beings and rats and cockroaches. They will survive and many other species will not survive whatever we do. So risk is something we can determine from the present day, but also we can test when we look at mass extinctions in the past. So this is where we come back to palaeontology, because I think most people here know that the end of the dinosaurs was marked by a mass extinction. Many millions or thousands of species died out rather rapidly. The cause of that extinction definitely was largely the impact of a meteorite, a huge asteroid, maybe ten kilometres across, and the model for extinction of the dinosaurs 66 million years ago was the asteroid hit the Earth - this is unpredictable, when this may happen or not - it penetrated into the crust, it vaporised, and all that rock of the asteroid plus the crust that it had penetrated turned into rocks and dust, mainly dust.
This was thrown up high into the atmosphere and went all round the Earth, blacking out the sun, and so that you get two effects there, no light, no heat. So there was a cessation of photosynthesis. The plants died. There was darkness and cold. So this was not good for dinosaurs and other groups that enjoyed the warm climates, and so you get extinction. And you might think, of course, ‘What do we learn from this?’ Yes, that’s all very well, but that’s not something we can do anything about really. And indeed, asteroids do come close to the Earth from time to time. Earlier this week, one did. Luckily it didn’t hit the Earth. We can’t really prepare. But the key point is that the other mass extinctions in the history of life were not caused by impact. They were caused by climate change. Immediately, you can see now how that matters. I will briefly characterise one of them that I have worked upon. At the end of the Permian Period, 250 million years ago, there was another major extinction.
This was before the dinosaurs. And the sequence of events was that massive volcanoes errupted in Russia. They were so huge that they poured out enormous amounts of lava, of course, but more importantly, they poured out gases into the atmosphere, including carbon dioxide. And carbon dioxide is famous as a greenhouse gas, meaning it heats the atmosphere. We have primary evidence that around the equator, ocean temperatures warmed up to 40 degrees plus. So this is like a very warm shower. You might think that’s OK. Maybe for 10 minutes but not for day after day after day. And so life had to progressively flee out of the equatorial zones. It became crowded at the poles and there was great extinction. So we learnt from that that carbon dioxide and global warming can cause extinction whatever the cause of that carbon dioxide, whether it comes from volcanoes or human activity. So we’ve learnt three things that we can illustrate and use for predicting into the future, what may happen to life.
We’ve learnt that we can calculate the rate of extinction by looking at historical extinctions and at that rate of extinction, even at the minimal figures, it’s at least one hundred times what it ought to be. Secondly, we’ve learnt something about risk, which species are most at risk of extinction, and I think that’s fairly straightforward. But we need the evidence to be able to argue the case. And thirdly, we’ve learnt that the whole history of the Earth records a rich record of climate change. We don’t need to do experiments, we don’t need to imagine what a world would be like without the polar ice caps. It has existed and we can study it. So to conclude, my aim has not been simply to spread doom and gloom, but to indicate that we have the power to change. And in order to change, we have to accept reality along the lines that we’re mentioning. And we have to ask the right questions about what we should do. And in order to decide what we should do, we need to use evidence.
And some great evidence comes from the history of the Earth and the history of life. Thank you very much.