The Direction of Evolution

WIE: You also make the case that organic evolution has a direction.

RW: Yes, in the sense that I think the evolution of intelligent life—or the evolution of life with an intelligence, something like the human intelligence—was very likely. That's not to say that every lineage gets more and more complex all the time, by any means. But there is enough growth in complexity and intelligence in the ecosystem as a whole that sooner or later I think you are very likely to wind up with a species smart enough to set in motion this second process of cultural evolution in a big way, which is what our species did.

As with the argument about direction in cultural evolution, this is controversial. People disagree about it. But at the same time, there is some factual basis for the argument. For example, multicellular life was invented independently multiple times, and a number of other key thresholds in the evolution of intelligence were passed through independently more than once. And that's evidence that, sooner or later, they were fairly likely to happen. That's evidence that there was a fairly strong evolutionary dynamic behind them. Of course, you can't go back and replay the tape. We can't conduct the whole several-billion-year-old experiment over again. So the arguments will always be somewhat speculative.

The question is: How likely was it that greater complexity and intelligence would arise? And there I would not just point to the fact of the growth of complexity and intelligence. Again, I would say we have to look at the dynamics that got us here, and at the thresholds we had to pass through, such as multicellularity. Or little things like the grasping appendage, which was vital to our manipulation of tools, which itself then accelerated the growth of human intelligence. You look at these thresholds and try to figure out, "Why did we pass through them? How likely were we to pass through them? How many different times were these thresholds passed through independently in the course of evolution?" And that's the kind of evidence that I think is most germane to the question of how likely was the growth in complexity and intelligence.

WIE: And you believe that this entire process—the fact that these thresholds have been repeatedly passed through in evolution to create greater intelligence and greater complexity—occurs as a result of natural selection.

RW: I think that you can satisfactorily explain this in terms of natural selection, yes. We can even explain something as ephemeral as "love." We do have this genetically based capacity for empathy, for love, for affection, for compassion. The first time this showed up in our lineage is in the love of kin. Then, subsequent to the invention of love, an evolutionary dynamic known as "reciprocal altruism" kicked in. That's what gives us the capacity to feel pretty deep affection for people we're not related to, and to build up bonds of trust with them and feel real compassion and real empathy for them. So, I think there are fewer and fewer fundamental challenges to the theory of natural selection, in that sense.

And, by the way, the dynamic of kin selection, which gave birth to love, is something that has manifested itself repeatedly, independently. So if you accept the idea that a fairly complexly sentient organism was bound to show up sooner or later, you have to include that the likelihood of the evolution of love was fairly high, too. Because in complexly sentient beings, the dynamic of kin selection is manifested in love.

But I'd like to get back to your question. While I think natural selection provides a satisfactory account for this, I do think there is still one massive mystery, and that is why consciousness, or sentience, exists at all, why there is subjective experience. And I don't think many evolutionary biologists appreciate the depth of that mystery; although some great ones do, like John Maynard Smith. The more I say about that, the less progress we'll make. Consciousness is just one of those things that as soon as you start talking about it, all the people who disagree with you get turned off and don't even understand what you're saying, and all the people who already agree with you don't need further enlightenment, so why go on? It's just—

WIE: Let's go there.

RW: Well, don't say I didn't warn you.

The Problem of Consciousness

WIE: I found it very intriguing in Nonzero that you talk about consciousness as a mystery that science, I think you say, can't solve. It hasn't, certainly.

RW: It certainly hasn't solved the mystery and it's hard to imagine that it would, in part because consciousness doesn't have what scientifically explicable phenomena need, which is public observability. Anything that is to be explained scientifically has to be something that you can point to—point to the physical phenomena and say, "See, I'm predicting that it will behave like this when you do that." Consciousness, by definition, doesn't fall into that category. Now, of course, you can register brain waves and you can do MRIs, and you can look at various physical manifestations of consciousness, but by definition that's not consciousness itself. Consciousness itself is a subjective experience. So it's very hard to imagine how science would really go about tackling the fundamental problem of consciousness. In any event, I certainly don't think it has handled it successfully to date. And there are too many people who are under the impression that science has answered all the important questions in the world or can answer them.

One reason I think it's fascinating that science can't handle this question, at least so far, is that the existence of subjective experience, of consciousness, is the source of all the meaning in the world, so far as I can tell. If I told you that there was a planet out there that looks just like Earth, and there are these things that look just like people, and they walk around doing exactly the things we do, and they utter phrases and stuff, but they have no subjective experience, it isn't like anything to be them. They are zombies. You would probably think, "Well, who cares what happens to that planet?" And I would agree. I would think, "Well, there's really nothing especially immoral about annihilating some of those creatures on that planet because we are not going to cause them any pain by doing that, and we are not going to deprive them of any future happiness or anything. So, who cares?" In my view, the whole basis of meaning and of moral significance is the fact that it is like something to be alive. And that is the one thing that, it seems to me, science cannot explain.

WIE: What role do you see consciousness playing in human evolution?

RW: Well, that's the mystery. A common view among scientists, and one that is not entirely implausible, is that consciousness is a mere side effect. It's an epiphenomenon. In other words, it really plays no role. Like when you move your hand and it makes a shadow, all the action is in the hand, not in the shadow. The shadow's not doing anything. That's what an epiphenomenon is. It's at least an easy answer to visualize clearly. I know exactly what they mean when they say that. In a way, it's intuitively attractive to me precisely because it's a clear, comprehensible answer.

So let's take the example of love: what's being selected for by natural selection is altruistic behavior. And then as it happens, the neural processes that give rise to altruistic behavior also give you the feeling of love. But that's just a kind of lucky coincidence in this view. So what's always being selected for is behavior, or the neural mechanisms governing the behavior, but the subjective experience per se is not being selected for; it is just a by-product. That is the view of consciousness as an epiphenomenon. And as I said, it's in many ways an attractive view, but it does raise the question of what consciousness is doing here if it doesn't have a function. So the epiphenomenalist position is, in a way, the scientifically most attractive view, precisely because it is so clear and doesn't force you to rethink the nature of causality.

But it does pose that one very challenging question, "Well, then, why is consciousness here if it has no function?" Now, the alternative to that, at least the main alternative as I see it, is to say that consciousness actually does play a causal role in the world. But then you are getting back to some kind of Cartesian dualism that is itself a challenge to the principles of science because science sees all the causality as residing in the material world. So one way or another, it seems to me, consciousness is this profound problem for science. Now, there are people who think they have a way around this, but I disagree. Yet, I have to add, consciousness is such a perplexing problem that I don't think anyone's view deserves to be dismissed out of hand. I don't know of anybody who seems to have the problem totally under control.

As I see it, there is really no way around consciousness being a fundamental mystery to science. If you take the Cartesian dualist approach, then it's a real problem for science at the most fundamental level, because it challenges the whole basic assumption of science that all causally significant things are happening in the material, publicly observable world. If you take the epiphenomenalist approach, it's reduced to not necessarily a fundamental problem, but a really perplexing question.

Suggestions of Purpose

WIE: Let's talk about purpose and evolution. You're very clear that evolution has direction. What are you saying about purpose?

RW: Well, I'm saying that the direction is at least suggestive of purpose but at the same time I'm conceding that that's all it can be. Suggestive is the most it can be because whether something has purpose is just a very difficult question. Unless you know that it was designed and you know what the designer was, you can never be sure whether something has purpose. You can make an educated guess, based on the way it looks.

In order to confidently assert the purpose of something, you have to know what the thing or process was that designed it. And so, too, with any human artifact. You can look at a car and be pretty confident that it's designed to move along the road, but the reason you are 100 percent sure is because you know who designed it and why.

Now when we look at the process of evolution, we're in the dark about the designer. That's the question we are grappling with here. If you accept directionality in evolution, you can say things like, "Well, like an animal, evolution seems to develop in a certain direction." Just as an animal matures in a certain direction, evolution seems to develop in a certain direction. And in fact, the combinations of genetic and cultural evolution have led the entire planet to seem increasingly like an integrated organism. Every decade it seems more like that. Every year the Internet seems more like it's drawing people into a giant planetary brain.

So you can point to these patterns that are suggestive of a larger purpose, but you just can't say for sure. My only point is that a scientific worldview gives you more evidence of some larger purpose at work than most scientists concede. And you can argue about what the purpose is, and you can argue about what the nature of the designer would be. It could be that some intelligence set evolution in motion and then went to another universe or something. But I think there is more evidence of purpose than most people concede.

WIE: So what you are saying is that the direction is suggestive of purpose, but that, by definition, if there is a purpose, we cannot know it scientifically.

RW: We can't know it scientifically, but I do think we can argue intelligently about it on the basis of scientific evidence. In other words, there are facts that are relevant to the question, even if it will forever remain a matter of speculation. For example, whether it's going to rain tomorrow is a matter of speculation. We cannot be 100 percent sure, but there are facts relevant to the question. There are facts that make it more likely or less likely that it's going to rain. So it's in that sense an empirical question, even if we can't pronounce on it with 100 percent certainty. And I think the purpose of evolution is that kind of question.

WIE: I also understand that the position you hold is not the same as the "intelligent design theorists," those who argue that there is some intelligent force or creativity that is at work in the unfolding of the greater complexity of life. How is what you are saying different?