Lecture 5.2Dawkins and Dobzhansky. Richard Dawkin s explanation of Cumulative Selection, in The Blind Watchmaker video.

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1 TOPIC: Lecture 5.2Dawkins and Dobzhansky Richard Dawkin s explanation of Cumulative Selection, in The Blind Watchmaker video. Dobzhansky s discussion of Evolutionary Theory. KEY TERMS/ GOALS: Inference to the best explanation. Natural Selection including Cumulative Selection and Adaptationism. READING: Watch Richard Dawkin s host a video on his book The Blind Watchmaker. You will find a link under Handouts Course Content. Read the Handout on The Blind Watchmaker in the same folder. Read Dobzhansky s Nothing in Biology Makes Sense Except in the Light of Evolution. Online at: or: Optional: review Alan Stairs, Chapter 2, The Design Argument from E- Reserves. (The reading from Coyne is not required (nor is it available on E- Reserves)) CONTENT: These lectures will offer a reply to Paley s Design Argument from Dawkins and Dobzhansky, so be sure you understand Paley s argument. I will summarize Richard Dawkin s explanation of Cumulative Selection, and then discuss Dobzhansky. Review of Paley. Recall that Paley gave us an argument to the conclusion that an Intelligent Designer (God) created humans and animals because humans and animals display teleology. Teleology is goal- driven complexity. Any system or trait displays teleology if it has complex parts working together to serve some purpose or function. A watch displays teleology because its gears, brass parts, and watch face work together in such a way that it is able to tell time. An eye displays teleology because its parts (lens, cornea, cones) work together in order to allow the organism to see. Paley draws an analogy between a watch and an eye because they both display teleology. He says that it is reasonable to infer that a watch must have been designed by an intelligent designer (namely humans), and so, too, the eye must have been designed by an Intelligent Designer (namely God). His conclusion is that humans and animals were designed by God. Here is Paley s Design Argument: P1. A watch displays teleology.

2 P2. The eye displays teleology. P3. Like effects have like causes. P4. A watch was designed, by an intelligent designer (humans). P5. Whatever displays teleology must be designed by something more intelligent than the thing itself. P6. Whatever displays teleology cannot have occurred by chance alone (in a single step). C. The eye was designed by an Intelligent Designer (God). You can see that the argument is by analogy. He takes two things, a watch and an eye that both display teleology, and says that if one of them is designed, then the other must be designed as well. Therefore, our eyes and organs, and any living thing on the planet are created by God. I wrote Paley s argument as a valid deductive argument. Recall that Deductive Arguments intend to prove that the conclusion must be true if the premises are true. But actually, Paley s argument has been taken to weaker than a PROOF of God s existence. Rather, his argument is considered a type of Inference to the best explanation, which is an argument that infers that the best explanation of X is the conclusion that the argument draws. In Paley s case, he inferred that since watches which display teleology were designed, that the best explanation for animal s traits (eyes, heart, etc.) is that it is designed as well. Here is another example of an inference to the best explanation: I was stepping on my lawn the other day and my foot fell through a wet patch in the grass. I knew that if sprinkler pipes leak or burst, then it causes soft wet patches in the lawn. I immediately inferred that the best explanation as to why the lawn had a soft wet patch was that the sprinkler pipes were somehow broken. I did not need to actually dig up the patch and check (empirically) that this is true in order to infer that it is. However, my argument does not PROVE that the sprinkler pipes MUST be broken. I simply gave the best explanation for why the grass was wet. (Indeed, after I dug up the grass I discovered the pipe did have a hole in it, and if you ve ever lived in a house with a sprinkler system, you can understand that the last few days of trying to fix the pipes have been draining for me.) An argument to the best explanation is much more common than a deductive argument. After all, how often do you hear people intend to prove that their conclusion must necessarily be true? They are more likely to offer the most likely explanation as to why something is the case. But arguments to the best explanation have a weak point namely, if a better explanation than the one being offered comes around, then you will accept that one as the best explanation. Indeed, in the last hundred years or so, Evolutionary Biologists have been offering arguments that give an explanation as to why humans have teleological traits. Their arguments intend to offer a better explanation than we were designed that way by God. In the 19 th century, Charles Darwin gave the Theory of Evolution, explaining that traits in animals arose because of the process of Natural Selection. I assume you all know a little about Evolutionary Theory, so I ll be brief. (Alan stairs has a nice brief summary of Evolution as well). Richard Dawkins: The Blind Watchmaker. In the 1970 s an influential Evolutionary Biologist, Richard Dawkins, eloquently explained the idea of Natural Selection in his book The Blind Watchmaker. Kick back and watch The Blind Watchmaker (the link can be found in The Blind Watchmaker folder under Course Content), and read the handout as well. Be sure to watch all 47 minutes. (I know- - the video is old, and the visual effects are cheesy).

3 Dawkin s thesis is that morphological (body- structure) traits can be explained by Cumulative Selection. Take any morphology of an animal (i.e. feathers, eyes, hearts, lungs, tails, fingers, etc.). You can explain its existence by appealing to random genetic mutation and natural selection. To explain, let me offer a story. Suppose we have a species of cheetah who can run very fast. Their fast legs allow them to survive (by catching prey and outrunning predators), and to reproduce (where their fast legs are genetically transmitted to their offspring). Suppose a random mutation occurs in an organism that causes this organism to have even longer legs or stronger muscles, thereby giving this organism to have even faster running speed. This organism can outrun even more predators, catch even more prey, and so he can survive longer and reproduce more. His offspring will inherit faster running speed and be able to survive and reproduce more. Eventually, this better trait may reach fixation in the population of his species. Cumulative Selection is a process where traits are developed piecemeal, over thousands or millions of generations. Thus, traits that display teleology can be explained by a step- wise process where each of the complex parts are added or modified to work better than the last trait. The eye, for example, may have started millions of years ago with only a few rods and/or cones. But, by random mutation, eyes acquire more rods and/or cones. Millions of generations later, the eye may have millions of rods/ cones that enable creatures with those eyes to see better and thus to survive and reproduce better than creatures who have simple- structured eyes. The idea behind Cumulative Selection is that traits are modified piecemeal (by small changes due to genetic mutation), over millions of generations. Cumulative Selection is an ingenious theory that explains how complex traits can arise from simple (or dumb or blind ) processes. You must keep in mind that evolution has no target- - it is blind to the future. Natural selection selects better morphologies (like better eyes) by creating random mutations, and then letting animals die off if they have worse mutations who cannot survive the selection pressures of their environment. Selection is a misleading word for the process, so do not get confused. The process simply works by having animals with better traits (caused by random mutation, migration, genetic drift, genetic recombination, etc.) survive and reproduce better in its environment than animals with less adaptive traits. So, what does this have to do with Paley? Recall Premise 5 and 6 above: P5. Whatever displays teleology must be designed by something more intelligent than the thing itself. P6. Whatever displays teleology cannot have occurred by chance alone (in a single step). In premise 6, Paley assumes that if teleological traits are not designed by an intelligent being, then they must have arisen by chance alone, in a single step. For example, either a watch on the beach was designed (by a human), or there is some principle of order which had disposed the parts of the watch into their present form and situation (48). He envisions that the only alternative to intelligent design is that random forces of nature bring all the watch parts together in one single step. Dawkins agrees with Paley s 6 th premise. The chances of a trait like an eye was to be formed by chance alone, meaning in a single step, has the probability of a trillion to one equivalent to the probability of him guessing the combination of a bank safe. But there is another alternative explanation, other than that traits must either be designed or arise by chance. The alternative explanation is Cumulative Selection. So, Paley was working with the story that humans were designed, full- form, by God. Evolutionary theory, on the other hand, maintains that human s traits were modified in a step- wise fashion over millions of years. But,

4 Evolutionary Biologists say, Paley s 5 th premise is false (namely, whatever displays teleology must have been designed. ) Dawkin s account of Cumulative Selection is meant to offer a better explanation for why humans have eyes (and other organs) that look like they were designed (they display teleology). We can explain why the eye has the parts they do, and why they work together for the purpose of allowing the organism to see (and to survive and reproduce in its environment). Cumulative Selection is, therefore, an alternative to the Intelligent Design hypothesis. Cumulative Selection can explain teleological features, so it is not the case that an intelligent designer is the only solution. Dobzhansky: Nothing in Biology Makes Sense Except in the Light of Evolution. Dobzhansky s article is a classic in the field of Evolutionary Biology. It is very important to find his thesis and keep it in mind: He intends to explain why Evolutionary Theory is the best explanation for the diversity and unity of life on Earth. His take- home message, though, is invaluable: He argues that the belief in Evolutionary Theory does NOT imply that you need not believe in God. A faith in God and a belief in Evolutionary Theory are compatible (as long as you don t use the bible as a biology text. ) Let s tackle the first point about diversity and unity of life: *Diversity of Life. He mentions that animals vary in sizes (i.e. from 8 mm viruses to 30 meters- long whales); animal s structures vary (i.e. from single- celled organisms to vertebrate animals); animal traits vary as well (i.e. feathers, fingers, or brains); and animal traits have adapted to the most bizarre niches on Earth (i.e. a certain species of fungus that only grows on the rear of a beetle that only lives in some limestone caves in France; another is an insect that is able to live and feed in oil). Dobzhansky says, The only explanation that makes sense is that the organic diversity has evolved in response to the diversity of environment on the planet earth (3-4). The process of Natural Selection can explain why so many different kinds of creatures are around (random mutations create various traits to the point of forming new species), why they inhabit every niche on earth (creatures adapt to their environment), and why so many species become extinct (they were unable to adapt to the environment). But the alternative explanation, that God created such diversity, seems senseless. His argument is that most species that have lived on earth has become extinct. It seems senseless to fabricate a multitude of species ex nihilo and then let most of them die out (4). For example, there are 350,000 known species of beetles on earth. The British scientist, J. B. S. Haldane noted that If one could conclude as to the nature of the Creator from a study of his creation it would appear that God has a special fondness for stars and beetles. *Unity of Life: The genetic code for all life on earth consist of four chemicals that make up DNA chains. The method of translation from DNA to RNA is the same in all life. And, there are huge chungs of DNA sequences that are shared across all species (these chunks are called Hox genes, that is said to have been around since the origin of life). Some species share similar DNA sequences with each other (i.e. Humans and chimpanzee but not humans and fish). Dobzhansky explains how this unity make sense in the light of evolution: they are nonsense otherwise (p. 7). The unity of life can be explained by saying that all life sprung from a single origin. It is worth noting that during Paley s time, the explanation of living being s existence was offered by the doctrine of Creationism (see Stairs p ). According to Creationism, God created animals in a day and then humans in a day. This means that animals were created to have the morphological forms they display today (birds have

5 feathers, fish have gills, etc.) and the species do not change from generation to generation. Creationism also implies that every species is separate (birds are birds, not fish). Thus, there are as many origins of animals as there are species. Evolutionary theory, on the other hand, maintains that every living creature evolved from one common ancestor some sort of bacteria that sprung up (somehow) from chemical goop on Earth about 3-5 billion years ago. Through the process of evolution, new traits formed, creating what we call different species. Man s ancestors appeared about 2-4 million years ago which is quite recent. Dawkins is famous for explaining (elsewhere) that evolution has had enough time to create the diversity of species that we find on Earth, even though it takes thousands of generations for small changes in traits to reach fixation in a population of species. *Ecological niches: Evolutionary theory can explain why most drosophilid flies live in Hawaii: places other thatn Hawaii were already colonized by competitors, and so the flied occupied the newly- formed volcanic island after it became inhabitable. The alternative explanation? That the Creator lapsed into a fit of absentmindness, or created the drosophilid after he created the other animals, perhaps in order to occupy Hawaii (p. 9). Dobzhansky concludes that the best explanation for the diversity and unity of life is the process of Evolution and Natural Selection. Pay close attention to the second full paragraph of p. 10. It is worth quoting here: Does the evolutionary doctrine clash with religious faith? It does not. It is a blunder to mistake the Holy Scriptures for elementary textbooks of astronomy, geology, biology, and anthropology (10). Dobzhansky is arguing that it is a mistake to think that belief in Evolutionary theory is opposed to belief in God (as many people, such as Teilhard, suppose). He simply warns us not to take the Bible s word about how humans and animals were designed, because the Bible is not meant to be taken as a textbook on biology. So faith in God is compatible with belief in evolution. However, it is NOT compatible if you choose to believe that the Creationist story offers true facts about the world. To get true information about the world, it is best to turn to scientific experts in biology, geology, anthropology, etc. ASSESSMENT: To prepare for your exam, give a 1-2 paragraph explanation Cumulative Selection. How does it explain teleological features? Why is it an alternative account to Paley s Design hypothesis? DISCUSSION QUESTIONS: Dobzhansky argues Evolutionary theory is the only story that makes sense for the diversity and unity of life on earth. He offers some witty responses to the alternative story (that an Intelligent Designer created animals on earth). For example, he says that the diversity and unity of life is senseless as if God were playing a joke on humans. Can you defend Paley against Dobzhansky s attack that the Intelligent Design story cannot make sense of diversity and unity? Dobzhansky offers a third hypothesis (very briefly) that perhaps God created life, but then let Evolution take its course. This hypothesis joins Evolutionary theory and God. But note that if the question is Why is the eye designed the way it is? then the right explanation is Natural Selection, not God (Natural Selection was the process that formed the eye to be designed the way it is, not God s design). Keep in mind that if God created creatures, he created them whole, with all the parts that they have (I.e. he created bats with wings and humans

6 with appendixes). So even if you think that God initially started the evolutionary process, you can ONLY explain teleological features by appealing to evolution, NOT God s design. I leave this up to you to work out the details.

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