COVER STORY: SEPTEMBER 13, 1999 VOL. 154 NO. 10

Message from a Mouse
It takes more than genes to make a smart rodent, or high-IQ humans
By STEPHEN JAY GOULD

Every age must develop its own version of the un-obtainable and chimerical quick fix: the right abracadabra to select the winning lottery number, the proper prayer to initiate the blessed millennium, the correct formula to construct the philosopher's stone. In a technological age, we seek the transforming gene to elicit immediate salvation from within.

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The excellent and provocative study of Joe Tsien and his colleagues will, one may safely predict, be widely misread in the false light of this age-old hope--combined with some equally age-old fallacies of human reasoning.

The scientists bred strains of mice with extra copies of a gene coded for a protein that can facilitate communication between neurons. Since one popular theory of memory relates this primary mental capacity to an organism's ability to make associations--say, between a bee's buzz and the pain of its bite--this enhanced communication might promote the recording of associations within the brain, thus creating memories.

Pundits in our age of rapid misinformation will surely transmit the story as a claim that the gene for intelligence has been cloned and that a human smart pill for routine production of kiddie geniuses lies just around the millennial corner. None of this punditry, however, will bear any relationship to current realities or reasonable prospects for the short-term future. Even so, the mice studied by Tsien et al. could help us correct two common errors in our thinking about genetics and intelligence:

1. The labeling fallacy. Complex organisms are not the sum of their genes, nor do genes alone build particular items of anatomy or behavior by themselves. Most genes influence several aspects of anatomy and behavior--as they operate through complex interactions with other genes and their products, and with environmental factors both within and outside the developing organism. We fall into a deep error, not just a harmless oversimplification, when we speak of genes "for" particular parts or behaviors.

No single gene determines even the most concrete aspect of my physical anatomy, say the length of my right thumb. The very notion of a gene "for" something as complex as "intelligence" lapses into absurdity. Intelligence is an array of largely independent and socially defined mental attributes, not a measure of a single something, secreted by one gene, measurable as one number and capable of arranging human diversity into one line ordered by relative mental worth.

To cite an example of this fallacy, in 1996 scientists reported the discovery of a gene for novelty-seeking behavior--generally regarded as a good thing. In 1997 another study saw a linkage between the same gene and a propensity for heroin addiction. Did the "good" gene for enhanced exploration become the "bad" gene for addictive tendencies? Biochemistry may be the same, but context and background matter.

2. The compositional fallacy. Just as each gene doesn't make a separate piece of an organism, the entire organism cannot be regarded as a simple summation of relevant building codes and their action (a skeleton is not a head gene added to a neck gene added to a rib gene, etc.). The fact that complex systems like human mentality or anatomy can be easily disrupted by deficiencies in single factors does not validate the opposite claim that enhancement of the same factors will boost the system in a harmonious and beneficial manner. The potential "fixing" of specific abnormalities--the realistic hope of certain gene therapies for the near future--does not imply that we'll be able to bioengineer superathletes or superscholars. The remedy for a specific deficiency does not become an elixir for general superiority. I can save a drowning man's mind if I hold his head above water, but I can't make him a genius by continually adding more oxygen to his ordinary surroundings.

Ironically, Tsien's mouse gene disproves these two fallacies of genetic determinism from within. By identifying the gene and charting the biochemical basis of its action, Tsien has demonstrated how valuable and necessary environmental enrichment is for yielding a beneficial effect. This gene doesn't make a mouse "smart" all by its biochemical self. Rather, the gene's action allows adult mice to retain a neural openness for learning that young mice naturally possess but lose in aging.

Even if Tsien's gene exists with the same function in humans (a realistic possibility), we will need an extensive regimen of learning to make possible any benefit from its enhanced action. In fact, we try very hard--often without success, in part because false beliefs in genetic determinism discourage our efforts--to institute just such a regimen during a human lifetime. We call this regimen education. Perhaps Jesus had a good biological insight when he stated (Matthew 18:3), "Except ye be converted, and become as little children, ye shall not enter into the kingdom of heaven."

Stephen Jay Gould teaches biology and the history of science at Harvard and New York University.