The natural world around us is highly organised. You can see evidence for this around you all the time. The scientific community seem to be settled on the thought that this is because life on earth evolved under the influence of Darwinian natural selection. But what is the evidence that evolution happened? Can anyone plausibly deny that it happened and, if so, how?
And, more importantly, if we did evolve alongside other animals, does this mean that we need to fundamentally refine the way we think about what it is to be human?
Artwork by Conner Griffin: The Plain Creative Agency.
Music: Land of Destiny, from Premium Beat.
Episode Two. What you didn’t know you knew.
So, where are we? In Episode One, I talked about how we can know what truth is and we showed conclusively that there was an ultimate truth: the Omnitruth, and that we were able to establish a limited number of absolutely certain, if quite generalised facts about it. But we decided that beyond these few facts that the Omnitruth is ultimately unknowable. However, that does not mean that we can’t know a great deal about what is true if we first assume that the reality we see around really is real, and if we use what I called Best Guess Reasoning to look at the evidence around us and determine the most likely explanation for what is true. In Episode Three, where we will meet this mysterious being I have called Nova, I said I would begin to explain where meaning came in the universe, and we are nearly there, but first, I want to persuade you of something you perhaps didn’t know that you knew.
This episode is about evolution. Now it is possible already know that evolution happened and you won’t need pursuading, in which case I must apologise in advance for labouring the point. But because the point is key to the case I’m going to make in the podcasts, it is essential for me to establish the extent to which we can say it is true, so I’ll try to do it in a sufficiently novel and interesting way, to make it worth your while listening, whether you already knew it was true or not.
If you are near a window, take a look outside. Can you see some grass? Maybe some flowering plants? Both the grass and the flowering plants are likely to have stems and leaves which are green. Both kind of plant will have roots; they grow; and if in favourable conditions they will propagate: they will spread their seed and grow somewhere else as well. Starve them of light or water they will die. In fact, it is obvious that the grass is just a kind of plant that has very narrow leaves and doesn’t bother with the extravagance of producing fancy, coloured flowers. Maybe you can see some bigger plants, from your window, some of them might be shrubby, with thicker woody stems. Some of these might be taller and difficult to distinguish from a small tree. Then, perhaps in the distance you might see true trees. They might have broad leaves, like oaks, or needle leaves like pine trees, or maybe scaly leaves like cypresses. But generally, all these trees will have green leaves, all the trees have will have a mechanism for reproducing themselves they’ll have roots, bark, and branches and if we looked at them through a microscope, and studied their structure and biochemistry, we would see many more similarities. In other words, there is a clear pattern visible in all plant species, there is a continuum connecting a blade of grass with the great oak tree, and this is obvious to us in our everyday lives.
In the 19th Century the biologist Carolus Linnaeus, systematised the order he saw around him in nature. He gave each different species a Latin name, because Latin was the international language of science. Then Linnaeus put very closely related animals, plants and geological specimens into what he called genera, singular genus. For example, the lion was named, in Latin, “Leo” and grouped together with the tiger, called “tigris” in the genus panthera. He then attached the generic and species names together, so the lion became Panthera leo and the tiger, Panthera tigris. Other big cats like the jaguar and the two species of leopard were then included into the same genus. Then he created other genera for the other species of cat and included them all in what he called a “family”: the cat family: “Felidae”. Then he noticed that there were similarities between the cat family the bears, the dog family and the weasel family, so he included all of these families into what he called an order: “Carnivora” the meat eaters. But it didn’t end there. All these animals gave birth to live young (they didn’t lay eggs) and they nursed their young from a mammary gland, on the ventral part of the torso of their adult females. In other words they were mammals, and like most other mammals they were furry, and had other specific features such as more complex brains and a distinctive arrangement of the inner ear bones, which meant that they belonged in a more expansive group, a class, the Mammalia, which along with Carnivora, included the ungulates, (cows goats and pigs), bats, elephants, rodents and the primates, the family to which we belong, and as we now know the cetaceans (the whales and dolphins). In fact, there are now nineteen recognised orders in the class Mammalia. Another step up and we get to the phylum. The phylum to which we belong, Chordata, includes all animals with a spinal cord including not only the mammals but the reptiles, birds, amphibians (that’s frogs, toads and newts) and the fish. But it doesn’t stop there either; all the animals belong to a Kingdom. Within the animal kingdom there are a vast number of invertebrate species (these are animals without backbones) and there are many other kingdoms of living things apart from plants and animals, such fungi and bacteria. Linnaeus would not have been able to build his system had the relationships between all living things not been there in the first place.
He was rather less successful in grouping minerals into appropriate categories and his system is no longer used for them, for the rather obvious reason that minerals are not related to each other in the same way that living things are. Now in that last sentence I used the word related. In fact, as we have already discovered, Linnaeus used the word “family” as one of the distinguishing divisions in his hierarchy of life. But we have not yet reached the point at which we can say that the relationship between animals is familial. That is to say that I haven’t yet shown that organisms are related to each other in the way that you and I are related to our mothers, fathers and siblings. This is a question which I am going to put to one side for now. What I hope I have been able to satisfy you of is that there is a clear pattern of physical relationships between all living things, and I’m going to illustrate how powerful this idea is, by telling you a story from my own experience: a true story:
It was a still, beautiful evening and the light was dying a slow, gentle death, as the day faded away. I was on my way back from a writer’s retreat in South Wales with some uni friends, when I stopped the car to stretch my legs. I was somewhere in the Welsh borders, and I found myself near a small lake surrounded by trees. It was then it happened. I heard something I had never heard before, it was a loud Cronk sound, and I knew immediately what it was. At that moment I knew I was about to see something I had never seen before, and always had wanted to see. But what was it, and how did I know what it was?
My interest in what it is to be a human being, which led me ultimately to the question of what matters in the universe and why, all began with an interest in animals, especially birds. I don’t claim to be an expert exactly, but I have always loved observing them, especially their behaviour, and I do know quite a lot about them, especially British birds. For example, I knew about the crow family: the corvids. Carrion crows and rooks are about the same size, they are both black. Crows are glossier compared to rooks which are shaggier and more angular looking with feathery “trousers” that crows lack. Their tails are a different shape too, but the most obvious feature is the bare white skin at the base of the rooks’ bill. Because these birds look superficially similar, I can only reliably tell them apart if they are relatively close and in good light. Interestingly these two species make a similar caw sound, and I can’t always tell their calls apart either. Jackdaws are much easier to separate from carrion crows, they are also predominantly black, but noticeably smaller and they have grey shoulders, white irises in their eyes and they make a much more distinctive chack sound, which give them their name. There are more distant members of the crow family, but still recognisably crows such as magpies with their piebald plumage and their insolent chatter, and the brightly coloured European jays with their stubby wings and a horrible, discordant cacophony of a call that seems quite unsuitable for such an attractive bird.
While each of the corvid species has their own appearance and call, they are sufficiently similar so that you can easily see the relationships between them.
It was obvious that the call I heard that evening was that of a corvid, but that cronk sound was much deeper than the call of any carrion crow or rook. It could have only come from one bird, the magnificent king of the corvids, the huge, shy, relatively rare, mountain bird: the raven. When I looked up, I saw what I knew I was going to see: my first ever wild ravens. There they were, three of them, circling above the lake set dark against the dim sky like three great black portentous crosses.
What is the point of this story? Well, the more you know about nature, the more you can see how obvious the relationships between living things are. The depth and extent of the relationships might elude people who haven’t had the time, the interest or education to understand nature in depth. Nature is shot through with these similarities to an extent that most people simply do not realise. How many times have you seen a horse with feathers, or a fish with nipples? In fact, nature seems to be made up of these similarities. I didn’t need to use the crow family to illustrate the point; I could have talked about the pigeons and doves, the gulls and terns, the finches or the robins and chats. (If you live in America, by the way, your robin is not a true robin, it belongs to the thrush family.)
So what causes animals and plants to have such a clear organisational structure? Why is it like that? There doesn’t seem to be any obviously good reason that fish don’t have feathers, or that people don’t have antennae like bees. Before Charles Darwin explained how he thought evolution worked, it was believed that these relationships were explained as strands of thought in the Creator’s mind. The thought here is that God imagined birds, and then He subdivided His thought into thoughts about crows, pigeons and gulls and so on. But now, with the advent of DNA sequencing we can see that all life on the planet shares similar patterns in its genetic structure. If we can prove paternity in disputed legal cases using DNA profiling and we take this as proof of familial relatedness, we can now prove that the relationships between different species of living things are truly familial. The genetic data has proved that all life on earth evolved from an ancestor shared by all living things.
So case proved, evolution happened, Right? Or maybe not, still not convinced?
You would not be alone, there are those, who do not believe that evolution happened. But it is established scientific theory. It isn’t a belief system. I might say that I believe my name is Peter D. Fisher, but in that case, I’m using a figure of speech. I know what my name is. While this isn’t proof that it is omnitrue: There could in theory be a god who made me, and called me George, and I suppose he is entitled to name me, and despite what I think I know, my actual name might be George, and I can’t say that the fact of evolution is omnitrue either, but come on, let’s just face it I know I’m Peter Fisher, and by the same token and same standards of evidence, I can say I know evolution happened.
Still not sure? Maybe you think the genetic evidence isn’t strong enough on its own. Let’s look at this in a bit more detail. Let’s think about the fossil record, which I deliberately left out of my evidence for evolution. Unlike the relatedness between living things that could, theoretically, have been the result of different strands of thought in the creator’s mind, the fossil record does not avail itself of another explanation of being true. If the universe was created in six days and the creator rested on the seventh, as the Bible says, there wouldn’t be a fossil record, at least not one that shows organisms changing over time. The only other way we could deny the Omnitruth of the fact of evolution is that we are being tricked. In Episode One I talked about the philosopher Rene Descartes, who invented an evil demon as a thought experiment to prove that he existed as a thinking thing. Maybe it’s time for me to invent my own evil demon, let’s call him The Great Deceiver. The Great Deceiver could have conned us into thinking that evolution happened by planting false evidence. If he has, he is very clever. There isn’t time to go into too many details of how they know, but scientists know the age of rocks. New rocks are obviously laid down on top of older ones. Lava from volcanos usually flows out over the rocks below it, forming new rock layers, and sediments always form on top of rocks that are already there, so we can see that rock is laid down in layers, in what scientists call strata, typically the oldest rock will be at the bottom, youngest at the top. The Great Deceiver must have known this because he knew exactly what he was doing, he made sure there were no fossils in the oldest rocks, in slightly newer rocks he put evidence of microbial activity, and newer still he made incredibly detailed fossils of small, simple creatures that are almost always completely different from the creatures alive today. These creatures, from what we call the Cambrian period are so strange that the scientists who named them gave them names like anomalocaris (this animal is an anomaly) and hallucigenia (this animal is like a hallucination) – The Great Deceiver could then have put fossils of increasing complexity in newer and newer rocks, that looked more and more like modern animals until he got to rocks of the Mesozoic Era, which is made up of the Triassic, Jurassic and Cretaceous periods, at this point he seemed to get a creativity burst and made fossils of dinosaurs, but then seemed to get bored with them and abruptly faked the evidence of a massive meteorite impact so that it looked like all the dinosaurs became extinct. All that is except the small feathered beaked dinosaurs we call birds. And get this… He created an impact crater a hundred and thirty miles in diameter, near Chicxulub on the Yucatan Peninsula in Mexico, and buried it in newer rocks and sediments so it looked as if it had been there for over sixty-five million years. The devious old scoundrel must have known that geologists would come along looking for oil in the area, and that they’d find the compacted and pulverised rocks that make up the crater. From then on, he put more fossils in the rocks until the most recent rocks where he made fossils of beings in which it is hard to say whether they are animal or human. If the great deceiver really does exist, he’s not just clever he is incredibly industrious too. Most people will have seen pictures of the famous White Cliffs of Dover. These are made of chalk, and something like three hundred feet high. If you look at chalk grains under a microscope you will see… well… grains of chalk. If, however, you look at them at a much higher resolution in an electron microscope, they are revealed as the fossilised remains of tiny shelly sea creatures. The chalk downs of England cover a large part of the south east of the country, and would have spread across into France, until the English Channel opened and cut the French downs off from those here in England; so there must literally be trillions of these tiny fossils across this vast area. I don’t’ know what you think, but I think It is amusing almost to the point of hilarity to think of The Great Deceiver spending all that time making all those tiny little fossils and dropping them into place with a microscopic pair of tweezers.
Let’s get real. With the utter superabundance of evidence written into the fossil record, and other evidence that doesn’t come from genetics or the fossil record, which I haven’t been able to include in this short podcast, the case is massively beyond overwhelming. Evolution happened. The evidence does not allow any other interpretation, or as the evolutionary biologist Theodosious Dobzhansky put it, “Nothing in nature makes sense except in the light of evolution”. Which only leaves two options, people either have to accept that evolution happened or believe in the Great Deceiver.
Why is this important? Well, in his book, with the provocative, but accurate, title of “Darwin’s Dangerous Idea”, the philosopher, Daniel Dennett, described the idea of evolution by natural selection as “the single best idea anyone ever had.” We have known about this for more than a hundred and fifty years, now, but the full implications have not yet filtered into the groupthink of mainstream thought. It’s my belief that our cultural assumptions have not yet been fully updated.
Please don’t be misled by the term, Best Guess Reasoning. This way of determining truth is nothing to do with any kind of wild guess, or any kind of guess at all. It’s just that I couldn’t think of a better term. Best guess reasoning can give us truths, such as what my name is, the fact that here on earth heavy things fall downward, and the sun will rise tomorrow morning. Truths like “evolution happened” sit comfortably in that class of knowledge. And I can say it’s true, or my name isn’t Peter D. Fisher. But then you already knew that it had happened didn’t you, because you can see the evidence all around you every day?
There are those who will never accept that evolution happened. Some of them think that if it happened it somehow diminishes us: that we are lessened somehow, that evolutionary theory robs us of something essential and reduces us, because if it happened, they think, we are just mere animals and there is no sense in which humans are special. They are misinformed! In the next episode you will meet Nova and find out how spectacularly wrong that argument is.
See you in the next episode, and thanks for listening.