Saturday, September 5, 2009

Natural selection

Comments invited on this first draft of bit of the humanism book. It would be easy to get some detail about the science wrong. Please offer corrections or suggestions, however minor...

Another popular argument for the existence of God is the teleological argument or argument from design. Arguments from design begin with the observation that the natural world, or items within it, appears to have certain remarkable features – such as order and purpose - and conclude that God is the only, or at least the best available, explanation of those features.

Perhaps the best-known argument from design is that presented by William Paley in his Natural Theology, published in 1802. Paley argues that, were one to find a complex object such as a watch lying on the ground, it would be unreasonable to suppose that the watch came to exist by chance, or that it had always existed in that form. Given the clear purpose of the watch – to tell the time - and its highly complex construction geared to fulfilling that purpose, it is reasonable to suppose the watch was fashioned by an intelligent being for that purpose. But if that is a reasonable conclusion to draw in the case of a watch, then surely it is reasonable to draw the same conclusion in the case of a work of nature such as the human eye, which also has a purpose for which it is intricately and exquisitely engineered. That intelligent designer, supposes Paley, is God.

That a biological organ such as the human eye must have some sort of designer was accepted by very many, including even the scientist Charles Darwin, up until the Darwin developed his own alternative explanation of the existence of the eye – a theory that explains how the eye might evolve gradually over many millions of years without the aid of any intelligence.

The mechanism Darwin realized could account for the gradual evolution of the eye is natural selection. When living organisms reproduce, their offspring may differ slightly in inheritable ways. Plant and animal breeders take advantage of these chance mutations to breed new strains. For example, a dog breeder might select from each generation of a dog those that are largest and least hairy, eventually producing a whole new breed of huge, bald dog.

Darwin’s great insight was to recognise that the natural environment in which organisms are located will, in effect, also select among offspring. Organisms with a chance mutation that enhances their ability to survive and reproduce in that environment will be more likely to pass that mutation on. Organisms with a mutation that reduces its chances of surviving and reproducing in that environment will be less likely to pass it on. And so, over a many generations organisms will gradually adapt to their environments. Under certain condition, a whole new species may emerge.

Darwin called this mechanism “natural selection”, contrasting it with the “artificial selection” used by dog and plant breeders. Unlike artificial selection, natural selection does not require an intelligent mind to guide the selection process towards a particular end. Selection is now taken care of entirely by blind, unthinking nature.

There is overwhelming fossil and other evidence that the human eye did, indeed evolve slowly and gradually over millions of years, beginning perhaps with the chance appearance a single light sensitive cell in an organism living many millions of years ago, and that natural selection is indeed the main mechanism that drove this process. Indeed, eyes provide such obvious survival value to organisms that they have evolved independently at least forty times.

The discovery of the mechanism of natural selection led Darwin to reject Paley’s argument from design. Darwin wrote:

The old argument of design in nature, as given by Paley, which formerly seemed to me so conclusive, fails, now that the law of natural selection has been discovered.[REF4]

While the development of Darwin’s theory of natural selection, and, later, the theory of genetics (including the theory of genetic drift, another mechanism driving the process of evolution), resulted in a decline in the popularity of arguments from design, such arguments have recently been making something of a come-back. Two popular, more recent variants of the argument from design are outlined below.

31 comments:

Brian said...

Stephen, isn't it the argument to design? One is not arguing from a known design to a designer, that would mean the argument was already settled and it's just a question of the properties of the designer. One argues from the appearance of design to the claim that the appearance is indeed design. From there you logically infer that there must be a designer.

What I find interesting is how this argument was pretty much demolished by Hume and Kant before Paley, yet they never die. Humans have an amazing propensity to see teleology in unexplained processes.

On the topic of natural selection, I just started reading Dawkins' "The greatest show on Earth". Weird coincidence.

Mats 'mcv' Volberg said...

Once I wrote an essay on the question "Is there order in nature?" And one of the first things I did there was to distinguish between different meanings of order and trying to figure out what kinds of order we might expect to find in nature.

The point is that 'order' might mean the very same thing as 'plan', but it might also mean the same as 'pattern' which is fairly different from a 'plan' not to mention from 'taxonomy'. In other words it is not quite clear what is meant by the ID people when they say that there is order in the world and that order had to come there by some intelligence. And that issue could perhaps use some elaboration.

Psiloiordinary said...

Being really picky here so just ignore this is you think it's over picky;

Eyes don't take nearly that long to evolve - according to latest research anyway.

Just a thought,

Regards,

Psi

SgtSkepper said...

Very pedantic, but you write:

"Under certain condition, a whole new species may emerge."

which I guess should read "under certain conditions" or "under a certain condition".

Other than that, I couldn't fault it.

Tony Lloyd said...

My thought's echoed Brian's (the Hume and Kant references).

Maybe there should be some reference to Dawkins' conversation with Ayer (Dawkins doesn't specify, but others do). This is where Dawkins said that Darwin enabled one to be an "intellectually fulfilled" atheist. Ayer was puzzled, feeling that Hume had perfectly well established atheism well before Darwin.

Maybe something along the lines of Darwin being the "final nail in the coffin" or Darwin meaning you don't have to be a skilled philosopher to put the design argument to rest. Or even that post-Darwin every argument from design has an "another Darwin might appear at any minute" caveat.

(BTW I didn't think much of "The God Delusion". I'm 3/4 of the way through "The Greatest Show on Earth" and I have to say it's absolutely fantastic. I'm sure it would be misleading to subtitle it "all of biology is here" but it certainly feels like it. I now know stuff about embryology!)

Greg O said...

I'd like to second Brian's point: it's the argument *to* design, not *from* design. That there is design in the universe is what the theist needs to establish, not an already-established fact they can use to justify the inference to a designer.

Greg O said...

Another point that's already been made, but I'd also like to see some acknowledgement of the fact that teleological arguments faced serious and convincing challenges before Darwin ever saw a finch. (I'm thinking of Hume's Dialogues in particular.)

Mike D. said...

I'm no expert but suspect you may need to revise the sentence "There is overwhelming fossil ... evidence that the human eye did indeed evolve slowly over millions of years". I understand (1) that Homo erectus emerged only 1-2 Million years ago, and (2) that since eyes comprise soft tissues they tend not to fossilise well. A useful review of the sources of evidence is "The Origin of the Vertebrate Eye" by Trevor Lamb et al. in Evo. Edu. Outreach (2008) 1:415-426. See also the article at
http://evolution.suite101.com/article.cfm/evolution_of_the_human_eye
for reference to research that did rely on fossil evidence.
Good luck with the book.

Chris said...

Good, simple article. Just a couple of things:

1. There is a missing 'of' in the paragraph beginning "There is overwhelming fossil..." It should read "...chance appearance OF a single light sensitive cell..." I would also hyphenate 'light-sensitive', but that's just a stylistic point.

2. The 'independence' of the evolution of eyes in different phyla has received some interesting qualification recently with the discovery that the same group of homeobox genes are at the centre of very different eye designs. In the recent Cell documentary on BBC4, an experiment was shown that placed rat homeobox genes for the eye into a fruit-fly lava, which proceeded to develop fly eyes all over its body (i.e. not rat eyes).

It's not strictly relevant, possibly, but it might reflect poorly if some evolutionary fence-sitter later heard that this was the case, and that eye evolution wasn't 'truly' independent across the phyla, and that therefore using it to strengthen one of Darwin's arguments was suspicious.

Just a thought.

Chris said...

Incidentally, IIRC, 'argument from' is a standard philosophical phrase, and that the nature of the word 'from' is not concerned with the direction of the prevailing argument, but instead refers to the originating statements upon which the initial argument was based.

In this case, the concept originally put forward to explain the complex world was one of design, and so it is therefore said to be the argument 'from design'.

See also the Argument From Authority, Argument From Ignorance, Argument From Silence, etc.

Mike said...

I agree with Chris. "Argument from design" is not only the customary phrasing, but it makes sense. It is an argument for the existence of a creator god "from" the suppostition of intelligent design. Stephen is simply questioning the validity of the premise.

Greg O said...

Chris and Mike - surely arguments from silence start from silence ("Nobody's mentioned such-and-such being the case, so it isn't!"), arguments from ignorance start from ignorance ("We don't know how such and-such could be the case, so it isn't!"), and arguments from authority start from authority ("So-and-so says such-and-such is the case, so it is!")? The person advancing such arguments isn't trying to convince us that there *is* some relevant instance of ignorance, silence or authority - he takes it for granted in his premises.

In the same way (as you suggest, Mike), an argument from design would surely start from design ("There is design in the universe, so..."). But design arguments don't typically beg the question in that way. Rather, they start from the observation that things like eyes resemble things we know to have been designed (like watches) in certain respects - intricacy, fitness for purpose etc. - and go on to suggest that we are therefore justified in inferring that they, too, were designed.

To start by asserting that certain things in nature have been designed would just be silly (unless, I suppose, one's concern was to show that some favoured candidate were the designer responsible: "The eye was designed; the only person with the power, wisdom etc. to design it is Zeus; therefore Zeus dunnit", or something.)

Greg O said...

Sorry, still pondering.

Surely the following is an argument *from* X, *to* Y?

Wow! There's X!
If there's X, there must be Y!
So there's Y!

And surely in the case of a Paley-style design argument, X is something like "order and purposiveness" and Y is something like "design"?

Mike said...

First off, I suspect that Brian's original point may have been influenced by the fact that the logical syntax of "teleological argument" and of "argument from design" are inverted. From the teleological standpoint, a purposeful God is a given and therefore everything is "to" God's purpose. "From" the standpoint of design, a designer's existence is inferred.

In any event, Greg, I would just say that if the argument from design doesn't always begin so assuredly ("There is evidence of design in nature; design requires a designer; therefore...") it is simply because the premises are so dubious. Stephen's sentence reads: "Another popular argument for the existence of God is the teleological argument or argument from design." He is talking about an argument for the existence of God (i.e. a designer) from certain premises. Again, the preliminary questions that such an argument typically begs, as you put it (correctly I'd say), pertain to the soundness of the premises.

Magnetic Lobster said...

Even if you change "condition" to "conditions," I'm still not fond of the sentence "Under certain condition(s), a whole new species may emerge." Introducing the idea of certain (unspecified) conditions is a detour from the main point. I think it would be more clear if you said something along the lines of "These adaptations are in fact how new species emerge."

Greg O said...

Mike - I do take your point; you could, I suppose, have an argument of the sort you describe:

There is evidence of design in nature; design requires a designer; therefore there's a designer.

We'd agree, I think, that such an argument is trivial and question-begging. (Obviously in accepting the first premise - that there is evidence of actual design, and not just the appearance of design, in nature - you've already accepted the conclusion). It's analogous to the argument that since there's evidence of carpentry in a tree, there must be a carpenter.

But the example Stephen takes as his target is not a silly argument of that sort; it's Paley's argument, one which starts with the appearance of design and concludes that design really is what's going on. *That's* the sort of argument which is undermined by natural selection.

And neither argument gets you to God just as it stands, so it's not as if the first is and the second isn't an argument for the existence of God. They each just get us as far as a designer, leaving an extra step to be taken in identifying that designer as the Big Fella himself.

Brian said...

But the example Stephen takes as his target is not a silly argument of that sort; it's Paley's argument, one which starts with the appearance of design and concludes that design really is what's going on.

Indeed. It's an argument to design. Not a question beggining argument from design.

Mike said...

Greg and Brian: Just a few more points. Agreed, Paley's argument is an argument for design, but it is part of a chain of reasoning in which the ultimate consequent is a designer -- i.e. a creator god. Therefore the entire chain is an argument for the existence of God. The fact that the premises are not "settled," as Brian pointed out in his original comment, is the reason my syllogism was "silly," as Greg put it. As a figure of speech, "argument from design" is consistent with other arguments for the existence of God, such as the "argument from natural law" or the "argument from reason." So, as for "silly" -- let's not be!

Greg O said...

Mike, I hope you don't think I'm blaming you personally for advancing 'silly' arguments! I know the syllogism you offered was only supposed to be an example of a theistic move, and I think you agree it's a question-begging argument, which is all I meant by 'silly'.

Obviously Paley's chain of reasoning is supposed to lead *from* something to a designer God, just as other arguments do. But the 'something' in question is not design - it's the observed order, purposiveness etc. of certain features of the world. The existence of design, and of the designer it implies, is what his argument leads *to*.

Mike said...

Oh heavens, Greg. The "order" and "purposiveness" you mention would be the very definition of "design." As for the earlier use of the word "silly," don't worry. I understood (and agreed with) what you were saying. Cheers.

Greg O said...

Mike - you said:

'The "order" and "purposiveness" you mention would be the very definition of "design."'

Argh! No it wouldn't! The whole point, surely, is that through natural selection, order and purposiveness can arise in nature *without* any design going on.

I'm lost now. I thought you agreed that the presence of design in the natural world logically entails the existence of a designer? (That's why the now-famous 'silly syllogism' is question-begging). But if you think that, and also think that order and purposiveness = design, the theist is home free:

1. There's order and purposiveness (= design) in nature.

2. The presence of design logically entails the existence of a designer responsible for it.

3. So, a designer is responsible for the order and purposiveness in nature. (Now, who could it be...?)

Tony Lloyd said...

[Cough]

I don't think order and purpose should be conflated. The lovely pattern of changes in polarity in rocks either side of the Mariana trench is highly ordered. As a result we can track the changes in the earth's magnetic field. But there is no purpose to this.

An evolved flora and fauna is a prime example of order. The big argument is whether that is evidence for purpose. If you conflate the two then you really have to accept that the flora and fauna of the world have a purpose. A purpose is teleological and, thus, you accept design.

In this case you would be arguing from design.

If you take order on its own an then try and use that to bolster the acceptance of design you would be arguing to design.

Which brings me to my next point. Maybe Stephen would be best off lifting from Graham Priest's book in the same series:

"This argument is often called the 'Argument from Design' (for the existence of god). It might better be called the Argument to Design; but never mind that."

(Graham's discussion of the Argument from/to Design centres not on the likelihood of order without a god but on the likelihood of order with a god. The Argument to Design only works if the likelihood of the evidence (order) given god is greater than the likelihood of the evidence without god. (This is akin to saying that god explains the order we see better than naturalistic explanations). But, says Graham (and I think he's right) why should we expect "order" from "god"? The Arguer to Design still has to convince us that god's purpose was what we see. There's no guarantee, maybe a god would be happy on his own, maybe he would want a chaotic universe. Why should we think, for example, that an all powerful god would want human beings? The only argument I can think of is that we have human beings and, as god made them and is all powerful he must have meant them. But here, of course, we need to assume that god made the universe in order to prove that god made the universe.)

Mike said...

We should define the word "design." I was using it as a noun in the sense of an ordered and functional arrangement. "Functional" here can be synonymous with "purposive" in the sense of "adapted to an end" or "serving a purpose."

In my sense, the noun is consistent both with Darwin's theory and with the premise, "There is evidence of design in nature." Thus for me the problem is with the second premise, "Design requires a designer." I sense others share this understanding of the word "design," or else there would be no need for the prefix "intelligent" in the phrase "intelligent design." It would be redundant.

The verb "design" certainly requires an agent, and if the noun is derived from the verb, then -- you may have a point!

Greg O said...

Mike - OK, now you've spelled out what you understand by 'design' I see where we've been going wrong. Sorry, I think I was misled because you seemed to agree that 'There's design in the universe' begged the question (because it entails the existence of a designer.) I still think that's right - no carpenter, no carpentry; no designer, no design.

Tony - of course you're right in what you say about purpose, but I think purposiveness is a different matter - if by 'purposive' one understands 'serving or effecting a useful function though not as a result of planning or design' [definition from the Merriam-Webster online dictionary]. Eyes (for instance) do serve a useful function, even though they don't serve anyone's conscious purpose.

Apparently 'purposive' can also be used as a synonym for 'purposeful', though, which might explain the confusion. Obviously if we regard things like eyes as purposeful we'll get straight back to a designer.

Anonymous said...

I'd like to see you go head to head with Vox Day.

Each religion, by the help of more or less myth which it takes more or less seriously, proposes some method of fortifying the human soul and enabling it to make its peace with its destiny. ~George Santayana

If so, how can that possibly be a bad thing? You might like to argue it's a 'delusion' because it conflicts with science and evolution theory. So what? Has science always been right? They did, for example, think that the world was a flat place (in which we were in danger of running off the edges) for a very long time. And if we were desendents from Apes, who created the apes? We could go on and on here. Why would you try and put a damper on people's sense of peace? You know you are secretly itching to believe in something higher. Something that your heart can cling to. Something sacred. Something warm and fuzzy. Anything that's good for one's peace of mind is...good. What's to lose? Perhaps a mean, stingy pessimistic attitude toward life and end of life perhaps....?

Brian said...

Anonymous:

You might like to argue it's a 'delusion' because it conflicts with science and evolution theory. So what? Has science always been right?

Nope, and we only conditionally accept it as right now. But it's the best we've got. And it does a great job.

They did, for example, think that the world was a flat place (in which we were in danger of running off the edges) for a very long time.

Who is they? Scientists? Really? Science as it's construed now has only been around for 4 centuries or so. It was known then that the Earth was a globe. The ancient Greeks, the forerunners of science, worked out the world was spherical. The bible on the other hand talks of 4 corners of the Earth. I think you're blaming the wrong people for a flat Earth model.

And if we were desendents from Apes, who created the apes?

Who said apes were created? They evolved. No creator needed.

We could go on and on here.

Yep, and eventually we'd get to a point where we had no real evidence, and some hypotheses. We could honestly say we don't know, yet. What we shouldn't do is then say "God did it". Because that's just calling ignorance by another name.

Why would you try and put a damper on people's sense of peace?

The truth isn't about feelings. With your attitude, we should let stalkers harass the stalkees. Because, after all, telling them they're a stalker and preventing them from stalking or doing worse to the stalkee would upset their peace.

You know you are secretly itching to believe in something higher. Something that your heart can cling to. Something sacred. Something warm and fuzzy. Anything that's good for one's peace of mind is...good.

So you're all for legalization of mind-altering drugs then? They can provide all those feelings you talk about. After all, it doesn't matter if the feeling isn't real, it doesn't matter if it's a delusion. You've said so yourself.

What's to lose? Perhaps a mean, stingy pessimistic attitude toward life and end of life perhaps....?

Pascal's wager in one of it's many guises? I can't speak for Stephen, but I'd think living a lie, sweet as you might find it, would be psychologically bad, and probably injurious. Truth might hurt, but it'll set you free.

Tony Lloyd said...

Hi Anonymous

I don't quite see your point. "If so, how can that possibly be a bad thing?" Whether it's a good, bad, or indifferent thing that poeple believe falsehoods is a different question from whether or not they are falsehoods.

"You might like to argue it's a 'delusion' because it conflicts with science and evolution theory"

We can often see that something is wrong without knowing what is right. We can know that "Anonymous was born on 1st January 1000" is false without knowing what your correct date of birth is.

We can also distinguish between things as to how near the truth they are, without the chosen proposition actually being true. "The earth is a sphere" is false, as is "the earth is flat". Yet one is a reasonable approximation, the other is bollocks. A bit like evolution and creation really. Take any detailed theory of evolution and it will be incorrect in places. It will thus, strictly, be false yet a reasonable approximation. Take any theory of creation and it will be bollocks.

Dr A said...

Oh, biologists usually fear to tread where philosophers roam, but here goes. To those of us who examine nature closely there are patterns (e.g., the one described by taxonomy) and many examples of the appearance of design (here using the word to mean only a deliberate organization). Clearly a mechanism exists that produces both such patterns and the appearance of design. And I say the appearance because much of what is termed design is upon closer examination a cobbled contraption that is biology.
RE the eye, as a botanist I've always found this a very human-biased example that fails to take into account biological diversity. A great many unicellular organisms in several major lineages have light sensitive pigments, eye spots, because phytoplanktonic organisms need to know where the surface is to stay in the light rich top layer of oceans. The fossil record is silent on the origin of such features but sensitivity to light must date back to the dawn of the eukaryotic cell, a couple or three billion years ago, give or take. So sight, if taken broadly as the ability to sense and react to light, is quite ancient. But mostly I find that people simply don't understand how natural selection can operate, and in searching my distant memories, I cannot discover when came the dawn, but it certainly isn't intuitively obvious.

james said...

"There is overwhelming fossil and other evidence that the human eye did, indeed evolve slowly and gradually over millions of years, beginning perhaps with the chance appearance a single light sensitive cell in an organism living many millions of years ago, and that natural selection is indeed the main mechanism that drove this process. Indeed, eyes provide such obvious survival value to organisms that they have evolved independently at least forty times."

Is it not misleading to say that natural selection is the main mechanism that drove this process? Natural selection is a process that either culls or preserves a given mutation/organ. It is always random mutation that is the main driver in evolutionary theory, though it is rhetorically and intuitively not nearly so persuasive to say so - so I'll understand if you don't. To invoke the necessity of sight to life by way of explaining the prevalence of the eye may lead the unguarded layman to Lamarckian-teleological misunderstandings of neo-Darwinian theory. Then again the field of epigenetics appears to me to suggest that in some sense Lamarck was right, but I'm no expert.

Anonymous said...

Let's not forget that, even if the human eye had a designer, he/she/it would have to have been a singularly incompetent one (says someone whose partner has needed two cataract operations).

I recall my knee surgeon's secretary remarking that she'd love to get her hands on whoever designed the human body so badly.

John Doyle said...

Stephen,

Under certain condition [sic], a whole new species may emerge.

But, as Charles Darwin himself pointed out, our definitions of species are altogether arbitrary. It may be difficult to distinguish this new species from the aboriginal variety and there would be no clear point where this animal could definitely be classified as a new species. It must always be clear that the species label is something invented by man as a convenient means of classifying living organisms.