The Gene: Part Five

There is an old story, probably apocryphal, of a Boston surgeon who did lose his memory and could only recall his friends by the names of the various operations he had performed on them.

The bone-by-bone reconstruction of these specimens pointed to a strongly built, prominently browed species that walked upright on somewhat bowed legs—an ornery wrestler with a permanent frown.

Wilson drew his crucial insight from two giants of biochemistry, Linus Pauling and Emile Zuckerkandl, who had proposed an entirely novel way to think of the genome—not just as a compendium of information to build an individual organism, but as a compendium of information for an organism’s evolutionary history: a “molecular clock.”

Crucially, Wilson realized, this method of age reconstruction was entirely self-contained and independent of bias: it made no reference to the fossil record, to linguistic lineages, geologic strata, geographical maps, or anthropological surveys.

It is called the Out of Africa theory, or the Recent Out of Africa model (the recent reflecting the surprisingly modern evolution of modern humans, and its acronym, ROAM, a loving memento to an ancient peripatetic urge that seems to rise directly out of our genomes).

By studying the genetic characteristics of an individual you can pinpoint his or her origin to a certain continent, nationality, state, or even a tribe with remarkable accuracy. It is, to be sure, an apotheosis of small differences—but if this is what we mean by “race,” then the concept has not just survived the genomic era, it has been amplified by it.

Does knowing that someone is of African versus European descent, say, allow us to refine our understanding of their genetic traits, or their personal, physical, or intellectual attributes in a meaningful manner? Or is there so much variation within Africans and Europeans that intraracial diversity dominates the comparison, thereby making the category “African” or “European” moot?

Between 1890 and 1910, dozens of tests were devised in Europe and America that purported to measure intelligence in some unbiased and quantitative manner.

It morphed into the notion of “general intelligence” because of a hypothesis concerning the nature of human knowledge acquisition. And it was codified into “IQ” to serve the particular exigencies of war.

There can hardly be a more cogent genetic argument for equality. It is impossible to ascertain any human’s genetic potential without first equalizing environments.

We cannot shrug this proposition away by suggesting that the current construction of the IQ test must be correct since it predicts performance in the real world. Of course it does—because the concept of IQ is powerfully self-reinforcing: it measures a quality imbued with enormous meaning and value whose job it is to propagate itself.

When a distinct, heritable biological feature, such as a genetic illness (e.g., sickle-cell anemia), is the ascendant concern, then examining the genome to identify the locus of that feature makes absolute sense.

Internecine political movements broke out frequently, shuttering the streets and businesses for weeks.

You might imagine that the sharp vicissitudes of fortune had reshaped Tulu and Bulu in drastically different ways.

On the contrary: over the years, their physical resemblance had dwindled to the point of vanishing, but something ineffable about them—an approach, a temperament—remained remarkably similar and even amplified in its convergence.

And second, it reasoned that once established, the original random act had to be amplified and consolidated to fully engender gender.

The XY system discovered by Stevens and Wilson had an important corollary: if the Y chromosome carried all the information to determine maleness, then that chromosome had to carry genes to make an embryo male.

Women with Swyer syndrome have male chromosomes in every cell in the body—but with the maleness-determining gene inactivated by a mutation, the Y chromosome is literally emasculated (not in a pejorative but in a purely biological sense).

If genes determine sexual anatomy so unilaterally, then how do genes affect gender identity?

Pinioned to an identity that she found evidently false and discordant, she was anxious, depressed, confused, anguished, and often frankly enraged.

In some cases, the gender dysphoria was not as acute as David’s...

He had spent much of his life comfortably ensconced in a “normally quiet US government laboratory...jumbled floor to ceiling with beakers and vials,” studying the regulation of a gene called metallothionine—or MT—that is used by cells to respond to poisonous heavy metals, such as copper and zinc.

“Why was Lewontin, a formidable geneticist, so determined not to believe that behavior could be inherited?” Hamer wondered. “He could not disprove the genetics of behavior in the lab and so he wrote a political polemic against it? Maybe there was room for real science here.”

But the twin studies provided incontrovertible evidence that genes influenced homosexuality more strongly than, say, genes influenced the propensity for type 1 diabetes (the concordance rate among twins is only 30 percent), and almost as strongly as genes influence height (a concordance of about 55 percent).

The notion that genes, of all things, could predispose humans to acquiring particular “functional selves”—possessing particular variants of temperament, personality, and identity—had unceremoniously been drummed out of universities.

The concordance among twins for type 1 diabetes, an illness considered unequivocally genetic, is only 0.35.

It can produce the most sublime qualities in humans—exploratory drive, passion, and creative urgency—but it can also spiral toward impulsivity, addiction, violence, and depression.

Aspects of behavior relegated largely or even exclusively to cultures, choices, and environments, or to the unique constructions of self and identity, have turned out to be surprisingly influenced by genes.

His brother, with a genetic propensity for bipolar disorder, perceives that same conversation as a grandiose fable about his future: even the fruit seller recognizes his incipient fame.

The expression of end-1—i.e., the number of molecules of RNA made during a particular phase of worm development—varies between worms, most likely due to random or stochastic effects—i.e., chance. If the expression exceeds a threshold, the worm manifests the phenotype; if it is below the level, the worm manifests a different phenotype.

Genes must carry out programmed responses to environments—otherwise, there would be no conserved form. But they must also leave exactly enough room for the vagaries of chance to stick.

Here too, a “genetic memory” was evident: the children and grandchildren of famine-starved individuals tended to develop metabolic illnesses, as if their genomes carried some recollection of their grandparents’ metabolic travails.

If cells could be indoctrinated or de-indoctrinated by manipulating their gene memories, perhaps humans could be indoctrinated as well (recall Lysenko’s attempt to achieve this with wheat strains, and Stalin’s attempts to erase the ideologies of human dissidents).

In 1961, two experiments performed less than six months, and less than twenty miles, from each other would transform the understanding of genes and lend credence to Waddington’s theory.

The daughter of a civil servant and a schoolteacher, Lyon began her graduate work with the famously cantankerous Ron Fisher in Cambridge, but soon fled to Edinburgh to finish her degree, and then to a laboratory in the quiet English village of Harwell, twenty miles from Oxford, to launch her own research group.

Histones hang tightly to DNA and wrap it into coils and loops, forming scaffolds for the chromosome. When scaffolding changes, the activity of a gene can change—akin to altering the properties of a material by changing the way that it is packaged (a skein of silk packed into a ball has very different properties from that same skein stretched into a rope).

Histones hang tightly to DNA and wrap it into coils and loops, forming scaffolds for the chromosome. When scaffolding changes, the activity of a gene can change—akin to altering the properties of a material by changing the way that it is packaged (a skein of silk packed into a ball has very different properties from that same skein stretched into a rope).

The first changes were transient—no more, perhaps, than the turning on and turning off of genes that respond to nutrients in the environment.

Hormones fanned out between organs, signaling the potential long-term deprivation of food and auguring a broader reformatting of gene expression.

Experiments performed on worms and mice have also demonstrated the transgenerational effects of starvation, although it’s unclear whether these effects persist or are attenuated over generations.

Despite Menelaus’s admonitions, the blood of our fathers is lost in us—and so, fortunately, are their foibles and sins.

Mutations, the reassortment of genes, and the erasure of memories counterbalance these forces, enabling unlikeness, variation, monstrosity, genius, and reinvention—and the refulgent possibility of new beginnings, generation upon generation.

The parables of such scientific overreach are well-known: foreign animals, introduced to control pests, become pests in their own right; the raising of smokestacks, meant to alleviate urban pollution, releases particulate effluents higher in the air and exacerbates pollution; stimulating blood formation, meant to prevent heart attacks, thickens the blood and results in an increased risk of blood clots to the heart.

The truth turned out to be quite the opposite: just one molecule carries the code, and just one code pervades the biological world.

“It sometimes seems as if curbing entropy is our quixotic purpose in the universe,” James Gleick wrote.