Answering the oldest question

Originally published 29 September 1986

“Who am I?” It is the old­est ques­tion in phi­los­o­phy. Socrates asked it. Descartes asked it. Philoso­phers today are still ask­ing it. And sci­ence may be on the verge of break­throughs that will change for­ev­er the way we under­stand the question.

There are two parts of the self cur­rent­ly open to sci­en­tif­ic scruti­ny. The first was there at the begin­ning, genet­i­cal­ly encod­ed in that first cell that would become me—Homo sapi­ens, male sex, white skin, brown eyes, a ten­den­cy to bald­ness in mid­dle age. The sec­ond part is the trea­sury of expe­ri­ences stored in mem­o­ry — songs heard, visions seen, tastes, smells, plea­sures, trau­mas — avail­able for recall and asso­ci­a­tion. These things togeth­er help make the crea­ture that is unique­ly “I.”

There is grow­ing excite­ment in the sci­en­tif­ic com­mu­ni­ty about the pos­si­bil­i­ty of elu­ci­dat­ing more com­plete­ly both parts of the self.

Biol­o­gist Fran­cis Crick once esti­mat­ed that if the bio­chem­i­cal instruc­tions for build­ing a human could be placed into 500-page recipe books, more than 1000 vol­umes would be required. That much infor­ma­tion is con­tained in every human cell, on mol­e­cules known as DNA. A DNA mol­e­cule has the form of a spi­ral stair­case. Each step on the stair­way is a chem­i­cal unit called a nucleotide. On the human DNA there are 3 bil­lion steps. It is the sequence of the nucleotides along the stair­way that makes up the code of life.

In recent years mol­e­c­u­lar biol­o­gists have invent­ed tech­niques for deter­min­ing the sequence of nucleotides on seg­ments of DNA. Some biol­o­gists are now urg­ing a pro­gram to pro­vide a com­plete tran­scrip­tion of the human DNA. The task would be stag­ger­ing. With cur­rent tech­nol­o­gy it would require tens of thou­sands of per­son-years and more than a bil­lion dol­lars. In a few years time the devel­op­ment of auto­mat­ed sequenc­ing tech­niques will make the task more man­age­able. It now seems inevitable that some time with­in the next decade the entire sequence of 3 bil­lion nucleotides on the human DNA will be known. That’s a thou­sand times more chem­i­cal units than there are let­ters in this newspaper.

Blueprint for a human being

The human genet­ic code, once unrav­eled, will be stored in a huge com­put­er data bank. It will be avail­able to researchers in med­i­cine, genet­ics, and evo­lu­tion­ary biol­o­gy. It will be — lit­er­al­ly — a com­plete chem­i­cal blue­print for a human being.

Mean­while, researchers in psy­chol­o­gy, behav­ioral neu­ro­science, and neu­ro­bi­ol­o­gy, along with work­ers in the com­put­er-relat­ed dis­ci­pline of arti­fi­cial intel­li­gence, are gain­ing a deep­er knowl­edge of the bio­chem­i­cal basis of memory.

Progress has been rapid on sev­er­al fronts. First, researchers have iden­ti­fied cer­tain per­ma­nent struc­tur­al and chem­i­cal changes that take place in brain cells (neu­rons) when learn­ing occurs. Mem­o­ry involves the mod­i­fi­ca­tion of vast net­works of inter­con­nect­ed cells. Progress has been made in local­iz­ing the net­works in the brain that are asso­ci­at­ed with dif­fer­ent types of learn­ing. Final­ly, elec­tron­ic and math­e­mat­i­cal sim­u­la­tions of mem­o­ry net­works are clar­i­fy­ing how mem­o­ry works in the brain, and bring­ing clos­er the day when machines will be able to learn and remem­ber in much the same way we do.

The task of map­ping the bio­chem­i­cal basis of mem­o­ry will be even greater than that of sequenc­ing the human DNA. There are 9 bil­lion neu­rons in the human brain, and the con­nec­tions between them are of astound­ing com­plex­i­ty. Nev­er­the­less, many sci­en­tists believe that the study of the neu­ro­log­i­cal basis of learn­ing and mem­o­ry is enter­ing a gold­en age of rapid­ly-accel­er­at­ing knowledge.

And when we have a com­plete map of the human genet­ic mate­r­i­al, and a map of mem­o­ry net­works in the brain, will we know the self? Will the self be defined by a list of sym­bols in a recipe book of ten thou­sand vol­umes? Will we point to a com­put­er data bank and say “This is who I am”?

Some philoso­phers will have no trou­ble with the notion that the self can be defined bio­chem­i­cal­ly. Oth­ers will hold that a bio­chem­i­cal def­i­n­i­tion of the self is sim­plis­tic and exces­sive­ly reduc­tion­ist. All will agree that the human self is a thing of immense com­plex­i­ty and sub­tle­ty which for a long time (per­haps for­ev­er) will chal­lenge our full understanding.

But the gene maps and mem­o­ry maps will be made. They will advance our knowl­edge of our­selves. They will help us find cures for dis­or­ders of body and mind. They will open up poten­tial futures full of promise and dan­ger. And no philoso­pher who is inter­est­ed in that old­est of philo­soph­i­cal ques­tions can afford to ignore these remark­able devel­op­ments in science.

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The 21st cen­tu­ry has giv­en us a map of our DNA and the com­ple­tion of the Human Genome Project, as well as stun­ning advances in Arti­fi­cial Intel­li­gence and Machine Learn­ing. But are we any clos­er to answer­ing the old­est ques­tion? ‑Ed.