Missing Shade of Blue
Posts: 62
Joined: Dec. 2008
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| Quote | | This is a terrible way of thinking about it. Evolution doesn't think, doesn't plan, doesn't care how many species go extinct. It's not striving toward some specific goal. It just tinkers and kills. Your burden, if you are going to claim that this is insufficient, is to come up with a specific case where it is demonstrably insufficient. Not a contrived example with no connection to the real world. |
OK, I'll admit that I should try to avoid using language that suggests natural selection is an intentional agent. But the point I was trying to make didn't rely on those ill-advised rhetorical flourishes. I really don't understand what you mean when you ask for a specific case where evolution is demonstrably insufficient. I think there is only a specific case where this is true - inductive bias. As far as I'm aware, natural selection is perfectly capable of explaining all other functional traits.
The example I used may be a bit simplified, but is a real world example. The fact that you think otherwise suggests to me that there is something about the example you do not understand. So let me try one more time:
1. Humans have certain inductive biases (in the real world, not some contrived hypothetical world). A particular example is the tendency to think of the color properties of many sorts of surfaces observed under normal circumstances as projectible. My jacket is blue and I confidently project that my jacket will be blue tomorrow. I also confidently project that the next emerald to be found will be green.
2. These biases, considered collectively, are highly functional. They support inferences which allow us to plan and learn about the world successfully.
3. These traits were selected a long long time ago and have remained more or less fixed in humans for at least, say, the past 100,000 years. There have not been significant selective forces altering our most basic inductive biases for at least that long.
4. So biases that were selected for their immediate projectibility over 100,000 years ago remain projectible today. This is by no means unsurprising. There are a vast number of other potential inductive biases that would have been just as fit as the current one 100,000 years ago, but would not continue to track the structure of the world for the ensuing 100,000 years. Somehow, humans ended up with a set of biases that are quite extraordinarily functional.
5. Here are some hypotheses about why we ended up with biases that work today:
(a) Natural Selection. This can't be the answer. By 3, there has not been significant selection for these traits (because there has not been significant variation) in at least the past 100,000 years. So if there was selection for the biases, it happened more than 100,000 years ago. But, like I said, there are a vast number of possible biases that would have been just as fit 100,000 years ago as our actual biases, but would not have been as successful over the next 100,000 years. Natural selection cannot account for why we ended up with our particular bias rather than one of these less functional biases.
But perhaps you disagree that these alternate biases would have been as fit 100,000 years ago. Even though they were as predictively successful as the blue-green bias in that environment, perhaps the argument is that they were not as simple as the blue-green bias, and so imposed extra resource costs on organisms that adhered to them. This is the sort of argument keith was making earlier. See my responses to him and to Wesley on the previous page about how such judgments of simplicity already presume a certain inductive bias. There is, as far as I know, no bias-independent conception of simplicity on which blue-green is the simplest bias. In fact, there is no bias-independent conception of simplicity at all.
Finally, one could respond (as you did) that natural selection selected for the inductive biases that reflect the structure of the world. But selection could only have used information about the environment at that particular time, viz. 100,000 years ago (plus information about past environments stored in the organism's genome). And, like I said, there were a vast number of different biases which reflected the structure of the world at that time but would not have continued to reflect that structure as time went on. None of these biases were selected. The one that was selected is the one that continued to work reliably for the next 100,000 years.
(b) Morphological/Developmental Constraints. Perhaps biochemistry sets constraints on the sorts of inductive agents that can develop, and that explains why we ended up with this particular set of inductive biases rather than some other set. This might well be true, but it does not answer the question. The question is "Why do our inductive biases work so well today?" The answer can't be "Because they are one of the few sets of morphologically feasible biases." That doesn't address the question at all.
© Trivial. This is the response that basically rejects that the question is problematic at all. It's along the lines of "The world is blue and green, damnit, not grue and bleen like in your fantasy scenario. The organisms that evolve will be the ones who see things in blue and green." I hope it's clear now why this sort of response doesn't get to the issue I'm concerned with. I'm not questioning the fact that blue and green are natural predicates. I'm not postulating (as you suggest) some bizarre hypothetical world in which colors change. I'm saying, granted that blue and green are natural projectible predicates, what explains the evolution of organisms (like us) that know this, that have by and large the right sorts of inductive biases. It's a question about the evolution of an actual observable trait in the actual world, accompanied by an argument as to why this question is particularly problematic.
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