Why our brains can think about think­ing: An evo­lu­tion­ary his­tory

The Washington Post Sunday - - BOOK WORLD - RE­VIEW BY NICK ROMEO Nick Romeo is a critic and jour­nal­ist whose work has ap­peared in the New Yorker, the New Repub­lic and other pub­li­ca­tions.

One of the least mod­estly ti­tled works in the his­tory of phi­los­o­phy is René Descartes’s “The World.” Seek­ing to ex­plain ev­ery­thing from plan­e­tary or­bits to the prop­er­ties of mag­nets and vol­ca­noes, the 17th-cen­tury French poly­math jus­ti­fied this grandiose ti­tle by ex­plor­ing an as­tound­ing va­ri­ety of sub­jects. Though he has be­come posthu­mously fa­mous for his spec­u­la­tion that the ex­ter­nal world might not ac­tu­ally ex­ist, Descartes de­voted much of his life to con­sid­er­ing the me­chan­ics of pre­cisely how our world func­tions.

The philoso­pher Daniel C. Den­nett’s new book, “From Bac­te­ria to Bach and Back: The Evolution of Minds,” shows the same world-en­com­pass­ing am­bi­tion as Descartes’s mag­num opus. Den­nett writes with clar­ity and ease on neu­ro­science, chem­istry, com­puter sci­ence, lin­guis­tics, phi­los­o­phy, bi­ol­ogy and much else. But this pro­fu­sion of seem­ingly dis­parate ma­te­rial is not just a dis­play of en­cy­clo­pe­dic eru­di­tion. El­e­ments within each of these fields are rel­e­vant to the two ques­tions Den­nett wants to an­swer: “How come there are minds? And how is it pos­si­ble for minds to ask and an­swer this ques­tion?”

That the pur­suit of such fun­da­men­tal ques­tions would lead across the tra­di­tional bound­aries of many aca­demic dis­ci­plines is not sur­pris­ing. Per­haps also un­sur­pris­ing is the fact that com­pletely sat­is­fy­ing ex­pla­na­tions to these grand queries are some­what elu­sive. Den­nett quotes the physi­cist Emer­son M. Pugh’s pithy for­mu­la­tion of the dif­fi­culty: “If the human brain were so sim­ple we could un­der­stand it, we would be so sim­ple we couldn’t.” Con­sid­er­ing its vast am­bi­tions, Den­nett’s book is a fas­ci­nat­ing and provoca­tive in­quiry, a feat of in­tel­lec­tual syn­the­sis in the tra­di­tion of Steven Pinker’s “How the Mind Works” and Dou­glas R. Hof­s­tadter’s “Gödel, Escher, Bach.”

His nar­ra­tive begins with the pre­bi­otic chem­istry of mol­e­cules roughly 1.5 bil­lion to 2 bil­lion years ago. Be­fore there was dif­fer­en­tial re­pro­duc­tive suc­cess — a ba­sic as­pect of Dar­winian evolution — there were prob­a­bly vary­ing de­grees of per­sis­tence within pop­u­la­tions of mol­e­cules. A quasi-Dar­winian process would re­ward those mol­e­cules ca­pa­ble of per­sist­ing long enough to ac­cu­mu­late other changes that might in turn al­low for still longer per­sis­tence. Repli­ca­tion, Den­nett ar­gues, was just a par­tic­u­larly suc­cess­ful case of dif­fer­en­tial per­sis­tence that arose by chance. When two dif­fer­ent sin­gle-celled en­ti­ties col­lided and merged, the more com­plex cells known as eu­kary­otes were formed.

The ap­par­ent im­prob­a­bil­ity of such a gen­er­a­tive col­li­sion tempts many to in­voke a su­per­nat­u­ral de­signer. Den­nett freely con­cedes the im­prob­a­bil­ity of cer­tain cru­cial de­vel­op­ments in the his­tory of life, but he cau­tions against con­flat­ing the im­prob­a­ble with the im­pos­si­ble. “Evolution is a process that de­pends on am­pli­fy­ing things that al­most never hap­pen,” he writes.

This de­scrip­tion of evolution as a “process” uses neu­tral lan­guage, but Den­nett of­ten writes about evolution “de­sign­ing” or­gan­isms, en­gag­ing in “R&D” to test func­tions and be­hav­iors, and act­ing for “rea­sons” and with “pur­poses.” There’s a ven­er­a­ble tra­di­tion of sci­en­tists us­ing the lan­guage of in­ten­tion and mo­tive as a ped­a­gog­i­cal tool when ex­plain­ing evolution — think of Richard Dawkins’s book “The Self­ish Gene” or even Charles Dar­win’s phrase “nat­u­ral se­lec­tion,” which im­plies a se­lec­tor. Den­nett’s fre­quent per­son­i­fy­ing metaphors are hedged with the stan­dard cau­tions not to take them lit­er­ally, but they do re­flect a gen­uine con­vic­tion: that the de­sign pro­cesses of search and se­lec­tion that un­der­lie ev­ery­thing from com­puter pro­gram­ming to ar­chi­tec­ture are also at work in bi­o­log­i­cal evolution.

Bac­te­ria and Bach rep­re­sent extreme poles on a spec­trum that runs from the mind­less, bot­tomup de­sign work of nat­u­ral se­lec­tion to the highly in­ten­tional, top-down de­signs crafted by a bril­liant human mind. But the lat­ter ex­ists only be­cause of the for­mer — minds emerged from the mind­less, and com­pre­hen­sion from the un­com­pre­hend­ing. “A process with no In­tel­li­gent De­signer can create in­tel­li­gent de­sign­ers who can then de­sign things that per­mit us to un­der­stand how a process with no In­tel­li­gent De­signer can create in­tel­li­gent de­sign­ers who can then de­sign things,” he writes in a sen­tence that re­wards reread­ing.

One mem­o­rable ar­tic­u­la­tion of the idea that el­e­gant de­sign must im­ply a de­signer comes from Robert MacKen­zie Bev­er­ley, a 19th-cen­tury critic of Dar­win who ex­pressed his cri­tique of nat­u­ral se­lec­tion like this: “In or­der to make a per­fect and beau­ti­ful ma­chine, it is not req­ui­site to know how to make it.” MacKen­zie pre­sented this propo­si­tion as ab­surd enough to be self-re­fut­ing, but Den­nett em­phat­i­cally en­dorses this claim, ar­gu­ing that our fa­mil­iar­ity with in­ge­niously de­signed cul­tural ar­ti­facts mis­leads us into pre­sum­ing that struc­tures in the nat­u­ral world must also re­flect the work of some in­ten­tional de­signer. When a groundnest­ing bird dis­tracts a preda­tor ap­proach­ing its nest with a feigned in­jury dis­play, there is a good rea­son for its be­hav­ior, but the bird it­self does not have a rea­son. Its be­hav­ior ex­hibits com­pe­tence without com­pre­hen­sion.

Den­nett loves to or­ga­nize his ideas with al­lit­er­a­tive slo­gans: de­sign without de­sign­ers, com­pe­tence without com­pre­hen­sion, and rea­sons without rea­son­ers are among his fa­vorites. This ten­dency makes a cer­tain sense in light of a key ar­gu­ment he de­fends through­out the book: that memes, like genes, are in a per­pet­ual Dar­winian com­pe­ti­tion to re­pro­duce. Memes re­pro­duce cul­tur­ally, not ge­net­i­cally, spread­ing copies of them­selves in the minds of their hosts, and they evolve and spread much more quickly than the prod­ucts of ge­netic evolution. It’s true that the right com­bi­na­tion of luck and de­sign can spread a song, phrase or photo into the minds of mil­lions within a mat­ter of min­utes. Maybe Den­nett, with his catchy al­lit­er­a­tive phrases, is just try­ing to pro­mote the sur­vival of his own men­tal off­spring. He puts a more far-fetched spin on this idea in cer­tain pas­sages, sug­gest­ing that words may be par­a­sit­i­cally oc­cu­py­ing human brains to fur­ther their own re­pro­duc­tive goals. This is one of sev­eral de­ploy­ments of in­ten­tional lan­guage that do more to con­fuse than clarify the sub­ject of cul­tural evolution.

The book has other flubs and flops. Den­nett gets the et­y­mol­ogy of the word “on­tol­ogy” wrong, and he has a frus­trat­ing in­abil­ity to no­tice the achieve­ments of fe­male ge­niuses in the arts and sci­ences. (He musters a hand­ful, then claims there are no oth­ers.)

But the work as a whole is a de­light­ful sum­ma­tion of Den­nett’s dis­tin­guished half-cen­tury ca­reer pon­der­ing some of the hard­est ques­tions in sci­ence. It’s also a wel­come re­minder that philoso­phers, when they ven­ture be­yond the clois­tered bound­aries of schol­arly dis­putes, can still make im­por­tant con­tri­bu­tions to some of the fun­da­men­tal ques­tions that mo­ti­vated the birth of their dis­ci­pline in the first place.

FROM BAC­TE­RIA TO BACH AND BACK The Evolution of Minds By Daniel C. Den­nett Nor­ton. 476 pp. $28.95

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