Thoughts on “The Greatest Show On Earth” — chapter 3 — The Primrose Path to Macro-Evolution
In chapter 2, Richard Dawkins talked about artificial selection. In chapter 3, he moves on to natural selection. The title of the chapter is the intriguing “The Primrose Path to Macro-Evolution”, which led me to believe he would discuss my criticism of the previous chapter—namely, where new genetic information comes from. But no, the chapter doesn’t go there, but goes in a direction I didn’t expect. As far as I can tell, his objective in chapter 3 is to make one main point: natural selection is essentially the same mechanism as artificial selection, even though the selecting agent doesn’t consciously choose to do so. Oh, and ipso facto, evolution is true.
The first few sentences sum it up nicely:
Chapter 2 showed how the human eye, working by selective breeding over many generations, sculpted and kneaded dog flesh to assume a bewildering variety of forms, colours, sizes and behaviour patterns. But we are humans, accustomed to making choices that are deliberate and planned. Are there other animals that do the same thing as human breeders, perhaps without deliberation or intention but with similar results? Yes, and they carry this book’s softening-up program steadily forward.
That leads into descriptions of various plants and animals and their interdependencies, with the assertion that these plants and/or animals have been working essentially the same magic as artificial selection. But this time, it’s all-natural (with no artificial flavours, colours or preservatives added).
I say “assertion” because the chapter is distinctly unlike the previous chapter, lacking evidence to support the ideas. Rather than making direct observation of naturally-selected changes, Dawkins observes the interdependencies between creatures and asserts natural selection drove them to that point. I suppose he is expecting that by naturally following on from the previous chapter’s discussion on artificial selection, the validity of the next step (natural selection) is carried by the philosophical and intuitive appeal of the idea.
Starting with the section “Insects were the first domesticators”, Dawkins introduces the reader to some of the interdependencies in nature, such as the mutual dependency between flowers and the animals that pollinate them. I certainly give him credit for interesting and entertaining reading, and I appreciate his knowledge of the natural world and its scientific discoveries.
The first topic is sunflowers. As Dawkins points out, the sunflowers we see today have been significantly altered by artificial selection, for food, dyes and decoration. The Russians bred the huge sunflowers, apparently, and native Americans before that had done their own artificial selection.
But before that again, sunflowers, like all brightly coloured flowers, owed their very existence to selective breeding by insects.
Show us your evidence
The chapter is full of these assertions. What evidence does he put forward to support such statements? Very little that I could find in this chapter. Wait, I found something here that might qualify as evidence: Darwin found an orchid from Madagascar, Angraecum sesquipedale, that had an 11-inch tubular nectary. He made the prediction, from evolutionary theory, that there must exist a moth with an 11-inch proboscis, in order to pollinate the flower. Lo and behold, years later, the predicted moth was discovered. Hooray for evolution!
The objection which seems a worthy one is this: wouldn’t creationism naturally make the same prediction?
Evolutionists predict, creationists predict, we all predict survivors
Like Dawkins, creationists marvel at the interdependency of creatures in nature, as well as the complex mechanisms employed by plants and animals to achieve their business. It is no surprise to creationists that flowers should depend on insects, and insects depend on flowers. (One might even argue that such interdependency is more expected to be produced by divine creation than by evolution, though that is mostly a philosophical and theological argument.) Creationists could call such harmonious cooperation in nature “the greatest show on earth”, giving credit to divine providence. But the point is that both creation and evolution seek to explain the same thing, which is populations and ecosystems that work well, that are stable, in which each population of creatures has robust qualities that give it excellent chances of survival. “Isn’t it marvelous”, Dawkins says, describing the wonders of insects and flowers. “Isn’t it marvelous”, also say creationists. So the prediction of a moth that pollinates the orchid simply is not a smoking gun for evolution. To point out a plant or animal’s compatibility with its environment as evidence for one’s theory (be it evolution or creation) is circular reasoning.
So Dawkins describes the wonders of insects and flowers, amidst the assertion that the cooperation both drives, and is driven by, natural selection.
Dawkins’ description of natural selection has an intuitive appeal to it. It sounds more than plausible—it even has a sense of inevitability about it. It’s also a natural follow-on from artificial selection, so putting these ideas in sequential chapters makes sense. So the idea seems intuitively powerful. In one sense, the chapter seems odd in that it contains little evidence that the life has indeed come about by this mechanism (rather than by an alternative, e.g. divine creation). Dawkins relies on the inherent appeal of the intuitive power of the idea! At this point, I have two main objections.
That which explains everything explains nothing
The idea of natural selection, as explained here, seems almost limitless in its capabilities. So much so, that the Dawkins seems to think that describing how natural selection could have made insects and flowers what they are, functioning in a harmonious eco-system, is sufficient to win us to the theory. As I said before, to point out creatures’ excellent features as evidence for evolution is circular reasoning. A scientific theory needs to make testable predictions: if it is true, such-and-such is the way we expect the world to appear. If the facts contradict the prediction, then this would be evidence against the theory. But that is missing from the chapter.
Evolutionists sometimes criticise divine creation as being non-scientific because attributing something to God’s doing is not a testable hypothesis. There is much that could be said about this. At this point I’d like to point out that Dawkins has done much the same thing in this chapter: attributing much to natural selection, without a testable hypothesis. “How did this happen? Natural selection did it.” That is the mantra of the chapter, and it ironically echoes the atheist accusation against creationists—“How did this happen? God did it.”
The primrose path leads to a giant leap
The chapter contains the same gloss as the previous chapter, and relates back to chapter 3’s title: is this really the path to macro-evolution? How far can this process go? The chapter starts with a well-defined starting point (artificial selection) and segues into natural selection, but then tries to take a huge leap into the chasm, apparently hoping to muster up sufficient momentum to carry the reader all the way to... macro-evolution. But far from being hurled irresistibly all the way to the destination of macro-evolution, I feel prodded towards the likelihood that natural selection can confer certain robustness to populations of organisms.
Humans indeed select intelligently, and I agree that intelligence doesn’t fundamentally change the underlying genetic mechanism of selection, compared to natural selection. Same as in chapter 2, I expect that natural selection can be as successful as artificial selection—it is limited by the available gene pool. A population’s gene pool confers a measure of variety which can give a population robustness to better cope with a varying environment. I see Darwin’s finches as a great example of natural selection in the short term. The environment changed, and selection worked with the gene pool to achieve a beneficial result. Are there any limits to what this can achieve? Yes, the extent of the gene pool represents the extent of possible evolution in the short term.
Dawkins doesn’t really talk about any possible limitations of evolution by selection of a gene pool. He seems to prefer an optimistic view: macro-evolution is simply the short-term change we see in artificial selection, multiplied by lots of time:
The difference between any two breeds of dog gives us a rough idea of the quantity of evolutionary change that can be achieved in less than a millennium. The next question we should ask is, how many millennia do we have available to us in accounting for the whole history of life? If we imagine the sheer quantity of difference that separates a pye-dog from a peke, which took only a few centuries of evolution, how much longer is the time that separates us from the beginning of evolution or, say, from the beginning of the mammals? Or from the time when fish emerged on to the land? The answer is that life began not just centuries ago but tens of millions of centuries ago.
Dog breeding seems to represent a best-case scenario for natural selection, blessed by dogs’ gene pool. Can it progress that easily, indefinitely? Even Dawkins says, while discussing canaries:
Domestically bred songs are longer, louder and more frequent than the wild ancestral type. But all these highly prized songs are made up of elements that occur in wild canaries, just as the habits and tricks of various breeds of dogs come from elements to be found in the behavioural repertoire of wolves.
What if the dog breeder tries to be ambitious, and aims for breeding a cat—but the genes for meowing or grooming just aren’t there? Or using my previous example of the blue rose, what happens if an aspiring breeder discovers that, unlike their previous easy successes in rose breeding, the blue rose is stubbornly elusive. How much time would they need then, persisting in artificial selection, to finally achieve blue? Likewise what if a changing environment would metaphorically demand a rose to be blue? If nature is not exceedingly patient, surely the creature must instead face extinction.
But what if... although blue is too difficult a path to take, there exists some other evolutionary path that takes the population in a useful direction? Perhaps I’m just being too picky? What if the trick is finding an easier, more fruitful path forward?
Thou shalt mutate
But still, gene pools aren’t infinite. No matter what path we might choose, shuffling those genes, eventually there must be boundaries. Despite the wonders of dog breeding, gene pools are most definitely finite. The gene pool of the Cambrian creatures surely did not contain the genetic information for fur, mammary glands or feathers. Shuffling genes doesn’t get you anywhere; mutations would be needed.
So if Dawkins is really going to talk about the path to macro-evolution, he can’t just talk about sufficient bucket-loads of time. He must elaborate on the questions of mutations, the creation of new genetic information, the difficulty (or otherwise) of finding a plausible winding path of gradual genetic change to a complex new feature. Therein lie numerous essential questions.
But for now, the book will focus on the element of time by the truckload. The next chapter is all about time, and how much of it evolution has to work its magic.