science

Une réac­tion à la der­nière annonce de l’administration Bush qui se drape de l’argument plu­ra­liste pour défendre l’enseignement du créa­tion­nisme (pudi­que­ment appelé «intel­li­gent design»). C’est Daniel Dennett qui écrit. C’est juste, intel­li­gent et, comme il se doit en temps de guerre, efficace…

PRESIDENT BUSH, announ­cing this month that he was in favor of tea­ching about « intel­li­gent design » in the schools, said,  « I think that part of edu­ca­tion is to expose people to dif­ferent schools of thought. »» A couple of weeks later, Senator Bill Frist of Ten­nessee, the Repu­blican leader, made the same point. Tea­ching both intel­li­gent design and evo­lu­tion  « doesn’t force any par­ti­cular theory on anyone, »» Mr. Frist said.  « I think in a plu­ra­listic society that is the fairest way to go about edu­ca­tion and trai­ning people for the future. »

Is « intel­li­gent design » a legi­ti­mate school of scien­tific thought? Is there some­thing to it, or have these people been taken in by one of the most inge­nious hoaxes in the history of science? Wouldn’t such a hoax be impos­sible? No. Here’s how it has been done.

First, imagine how easy it would be for a deter­mined band of nay­sayers to shake the world’s confi­dence in quantum physics — how weird it is! — or Ein­stei­nian rela­ti­vity. In spite of a century of ins­truc­tion and popu­la­ri­za­tion by phy­si­cists, few people ever really get their heads around the concepts involved. Most people even­tually cobble toge­ther a jus­ti­fi­ca­tion for accep­ting the assu­rances of the experts: «Well, they pretty much agree with one another, and they claim that it is their unders­tan­ding of these strange topics that allows them to harness atomic energy, and to make tran­sis­tors and lasers, which cer­tainly do work…»

For­tu­na­tely for phy­si­cists, there is no powerful moti­va­tion for such a band of mischief-makers to form. They don’t have to spend much time per­sua­ding people that quantum physics and Ein­stei­nian rela­ti­vity really have been esta­bli­shed beyond all rea­so­nable doubt.

With evo­lu­tion, however, it is dif­ferent. The fun­da­mental scien­tific idea of evo­lu­tion by natural selec­tion is not just mind-boggling; natural selec­tion, by exe­cu­ting God’s tra­di­tional task of desi­gning and crea­ting all crea­tures great and small, also seems to deny one of the best reasons we have for belie­ving in God. So there is plenty of moti­va­tion for resis­ting the assu­rances of the bio­lo­gists. Nobody is immune to wishful thin­king. It takes scien­tific dis­ci­pline to protect our­selves from our own cre­du­lity, but we’ve also found inge­nious ways to fool our­selves and others. Some of the methods used to exploit these urges are easy to analyze; others take a little more unpacking.

A crea­tio­nist pam­phlet sent to me some years ago had an amusing page in it, pur­por­ting to be part of a simple questionnaire:

Test Two

Do you know of any buil­ding that didn’t have a builder? Y/N
Do you know of any pain­ting that didn’t have a painter? Y/N
Do you know of any car that didn’t have a maker? Y/N

If you ans­wered YES for any of the above, give details:
Take that, you Dar­wi­nians! The pre­sumed embar­rass­ment of the test-taker when faced with this task per­fectly expresses the incre­du­lity many people feel when they confront Darwin’s great idea. It seems obvious, doesn’t it, that there couldn’t be any designs without desi­gners, any such crea­tions without a creator.

Well, yes — until you look at what contem­po­rary biology has demons­trated beyond all rea­so­nable doubt: that natural selec­tion — the process in which repro­du­cing enti­ties must compete for finite resources and thereby engage in a tour­na­ment of blind trial and error from which impro­ve­ments auto­ma­ti­cally emerge — has the power to gene­rate brea­th­ta­kingly inge­nious designs.

Take the deve­lop­ment of the eye, which has been one of the favo­rite chal­lenges of crea­tio­nists. How on earth, they ask, could that engi­nee­ring marvel be pro­duced by a series of small, unplanned steps? Only an intel­li­gent desi­gner could have created such a brilliant arran­ge­ment of a shape-shifting lens, an aperture-adjusting iris, a light-sensitive image surface of exqui­site sen­si­ti­vity, all housed in a sphere that can shift its aim in a hun­dredth of a second and send mega­bytes of infor­ma­tion to the visual cortex every second for years on end.

But as we learn more and more about the history of the genes involved, and how they work — all the way back to their pre­de­cessor genes in the sight­less bac­teria from which mul­ti­celled animals evolved more than a half-billion years ago — we can begin to tell the story of how pho­to­sen­si­tive spots gra­dually turned into light-sensitive craters that could detect the rough direc­tion from which light came, and then gra­dually acquired their lenses, impro­ving their information-gathering capa­ci­ties all the while.

We can’t yet say what all the details of this process were, but real eyes repre­sen­ta­tive of all the inter­me­diate stages can be found, dotted around the animal kingdom, and we have detailed com­puter models to demons­trate that the crea­tive process works just as the theory says.

All it takes is a rare acci­dent that gives one lucky animal a muta­tion that improves its vision over that of its siblings; if this helps it have more off­spring than its rivals, this gives evo­lu­tion an oppor­tu­nity to raise the bar and ratchet up the design of the eye by one mind­less step. And since these lucky impro­ve­ments accu­mu­late — this was Darwin’s insight — eyes can auto­ma­ti­cally get better and better and better, without any intel­li­gent designer.

Brilliant as the design of the eye is, it betrays its origin with a tell-tale flaw: the retina is inside out. The nerve fibers that carry the signals from the eye’s rods and cones (which sense light and color) lie on top of them, and have to plunge through a large hole in the retina to get to the brain, crea­ting the blind spot. No intel­li­gent desi­gner would put such a clumsy arran­ge­ment in a cam­corder, and this is just one of hun­dreds of acci­dents frozen in evo­lu­tio­nary history that confirm the mind­less­ness of the his­to­rical process.

If you still find Test Two com­pel­ling, a sort of cog­ni­tive illu­sion that you can feel even as you dis­count it, you are like just about eve­ry­body else in the world; the idea that natural selec­tion has the power to gene­rate such sophis­ti­cated designs is deeply coun­te­rin­tui­tive. Francis Crick, one of the dis­co­ve­rers of DNA, once jokingly cre­dited his col­league Leslie Orgel with «Orgel’s Second Rule»: Evo­lu­tion is cle­verer than you are. Evo­lu­tio­nary bio­lo­gists are often startled by the power of natural selec­tion to dis­cover an «inge­nious» solu­tion to a design problem posed in the lab.

This obser­va­tion lets us address a slightly more sophis­ti­cated version of the cog­ni­tive illu­sion pre­sented by Test Two. When evo­lu­tio­nists like Crick marvel at the cle­ver­ness of the process of natural selec­tion they are not ack­now­led­ging intel­li­gent design. The designs found in nature are nothing short of brilliant, but the process of design that gene­rates them is utterly lacking in intel­li­gence of its own.

Intel­li­gent design advo­cates, however, exploit the ambi­guity between process and product that is built into the word « design. » For them, the pre­sence of a fini­shed product (a fully evolved eye, for ins­tance) is evi­dence of an intel­li­gent design process. But this temp­ting conclu­sion is just what evo­lu­tio­nary biology has shown to be mistaken.

Yes, eyes are for seeing, but these and all the other pur­poses in the natural world can be gene­rated by pro­cesses that are them­selves without pur­poses and without intel­li­gence. This is hard to unders­tand, but so is the idea that colored objects in the world are com­posed of atoms that are not them­selves colored, and that heat is not made of tiny hot things.

The focus on intel­li­gent design has, para­doxi­cally, obs­cured some­thing else: genuine scien­tific contro­ver­sies about evo­lu­tion that abound. In just about every field there are chal­lenges to one esta­bli­shed theory or another. The legi­ti­mate way to stir up such a storm is to come up with an alter­na­tive theory that makes a pre­dic­tion that is crisply denied by the rei­gning theory — but that turns out to be true, or that explains some­thing that has been baf­fling defen­ders of the status quo, or that unifies two distant theo­ries at the cost of some element of the cur­rently accepted view.

To date, the pro­po­nents of intel­li­gent design have not pro­duced any­thing like that. No expe­ri­ments with results that chal­lenge any mains­tream bio­lo­gical unders­tan­ding. No obser­va­tions from the fossil record or geno­mics or bio­geo­graphy or com­pa­ra­tive anatomy that under­mine stan­dard evo­lu­tio­nary thinking.

Instead, the pro­po­nents of intel­li­gent design use a ploy that works some­thing like this. First you misuse or mis­des­cribe some scientist’s work. Then you get an angry rebuttal. Then, instead of dealing for­thrightly with the charges leveled, you cite the rebuttal as evi­dence that there is a «contro­versy» to teach.

Note that the trick is content-free. You can use it on any topic. « Smith’s work in geology sup­ports my argu­ment that the earth is flat, »» you say, mis­re­pre­sen­ting Smith’s work. When Smith responds with a denun­cia­tion of your misuse of her work, you respond, saying some­thing like: «  See what a contro­versy we have here? Pro­fessor Smith and I are locked in a titanic scien­tific debate. We should teach the contro­versy in the class­rooms. »» And here is the deli­cious part: you can often exploit the very tech­ni­ca­lity of the issues to your own advan­tage, coun­ting on most of us to miss the point in all the dif­fi­cult details.

William Dembski, one of the most vocal sup­por­ters of intel­li­gent design, notes that he pro­voked Thomas Schneider, a bio­lo­gist, into a res­ponse that Dr. Dembski cha­rac­te­rizes as « some hair-splitting that could only look ridi­cu­lous to out­sider obser­vers. »» What looks to scien­tists — and is — a kno­ckout objec­tion by Dr. Schneider is por­trayed to most eve­ryone else as ridi­cu­lous hair-splitting.

In short, no science. Indeed, no intel­li­gent design hypo­thesis has even been ven­tured as a rival expla­na­tion of any bio­lo­gical phe­no­menon. This might seem sur­pri­sing to people who think that intel­li­gent design com­petes directly with the hypo­thesis of non-intelligent design by natural selec­tion. But saying, as intel­li­gent design pro­po­nents do, « You haven’t explained eve­ry­thing yet, »» is not a com­pe­ting hypo­thesis. Evo­lu­tio­nary biology cer­tainly hasn’t explained eve­ry­thing that per­plexes bio­lo­gists. But intel­li­gent design hasn’t yet tried to explain anything.

To for­mu­late a com­pe­ting hypo­thesis, you have to get down in the trenches and offer details that have tes­table impli­ca­tions. So far, intel­li­gent design pro­po­nents have conve­niently sides­tepped that requi­re­ment, clai­ming that they have no spe­ci­fics in mind about who or what the intel­li­gent desi­gner might be.

To see this short­co­ming in relief, consider an ima­gi­nary hypo­thesis of intel­li­gent design that could explain the emer­gence of human beings on this planet:

About six million years ago, intel­li­gent genetic engi­neers from another galaxy visited Earth and decided that it would be a more inter­es­ting planet if there was a language-using, religion-forming species on it, so they seques­tered some pri­mates and gene­ti­cally re-engineered them to give them the lan­guage ins­tinct, and enlarged frontal lobes for plan­ning and reflec­tion. It worked.

If some version of this hypo­thesis were true, it could explain how and why human beings differ from their nearest rela­tives, and it would dis­con­firm the com­pe­ting evo­lu­tio­nary hypo­theses that are being pursued.

We’d still have the problem of how these intel­li­gent genetic engi­neers came to exist on their home planet, but we can safely ignore that com­pli­ca­tion for the time being, since there is not the sligh­test shred of evi­dence in favor of this hypothesis.

But here is some­thing the intel­li­gent design com­mu­nity is reluc­tant to discuss: no other intelligent-design hypo­thesis has any­thing more going for it. In fact, my far­fet­ched hypo­thesis has the advan­tage of being tes­table in prin­ciple: we could compare the human and chim­panzee genomes, looking for unmis­ta­kable signs of tam­pe­ring by these genetic engi­neers from another galaxy. Finding some sort of user’s manual neatly embedded in the appa­rently func­tion­less « junk DNA » that makes up most of the human genome would be a Nobel Prize-winning coup for the intel­li­gent design gang, but if they are looking at all, they haven’t come up with any­thing to report.

It’s worth poin­ting out that there are plenty of sub­stan­tive scien­tific contro­ver­sies in biology that are not yet in the text­books or the class­rooms. The scien­tific par­ti­ci­pants in these argu­ments vie for accep­tance among the rele­vant expert com­mu­ni­ties in peer-reviewed jour­nals, and the writers and editors of text­books grapple with judg­ments about which fin­dings have risen to the level of accep­tance — not yet truth — to make them worth serious consi­de­ra­tion by under­gra­duates and high school students.

So get in line, intel­li­gent desi­gners. Get in line behind the hypo­thesis that life started on Mars and was blown here by a cosmic impact. Get in line behind the aquatic ape hypo­thesis, the ges­tural origin of lan­guage hypo­thesis and the theory that singing came before lan­guage, to mention just a few of the enti­cing hypo­theses that are acti­vely defended but still insuf­fi­ciently sup­ported by hard facts.

The Dis­co­very Ins­ti­tute, the conser­va­tive orga­ni­za­tion that has helped to put intel­li­gent design on the map, com­plains that its members face hos­ti­lity from the esta­bli­shed scien­tific jour­nals. But esta­blish­ment hos­ti­lity is not the real hurdle to intel­li­gent design. If intel­li­gent design were a scien­tific idea whose time had come, young scien­tists would be dashing around their labs, vying to win the Nobel Prizes that surely are in store for anybody who can over­turn any signi­fi­cant pro­po­si­tion of contem­po­rary evo­lu­tio­nary biology.

Remember cold fusion? The esta­blish­ment was incre­dibly hostile to that hypo­thesis, but scien­tists around the world rushed to their labs in the effort to explore the idea, in hopes of sharing in the glory if it turned out to be true.

Instead of spen­ding more than $1 million a year on publi­shing books and articles for non-scientists and on other public rela­tions efforts, the Dis­co­very Ins­ti­tute should finance its own peer-reviewed elec­tronic journal. This way, the orga­ni­za­tion could live up to its self-professed image: the doughty defen­ders of brave ico­no­clasts bucking the establishment.

For now, though, the theory they are pro­mo­ting is exactly what George Gilder, a long-time affi­liate of the Dis­co­very Ins­ti­tute, has said it is: «Intel­li­gent design itself does not have any content.»

Since there is no content, there is no «contro­versy» to teach about in biology class. But here is a good topic for a high school course on current events and poli­tics: Is intel­li­gent design a hoax? And if so, how was it perpetrated?

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