the Third Twin (1996)

“The three of us should get together and decide what the hell we’re going to do. How about tonight?”

“I’m taking Jeannie to dinner.”

“Do you think that may solve the problem?”

“It can’t hurt.”

“I still think we’ll have to pull out of the Landsmann deal in the end.”

“I don’t agree,” Berrington said. “She’s pretty bright, but one girl isn’t going to uncover the whole story in a week.”

However, as he hung up he wondered if he should be so sure.

8

THE STUDENTS IN THE HUMAN BIOLOGY LECTURE THEATER were restive. Their concentration was poor and they fidgeted. Jeannie knew why. She, too, felt unnerved. It was the fire and the rape. Their cozy academic world had been destabilized. Everyone’s attention kept wandering as their minds went back again and again to what had happened.

“Observed variations in the intelligence of human beings can be explained by three factors,” Jeannie said. “One: different genes. Two: a different environment. Three: measurement error.” She paused. They all wrote in their notebooks.

She had noticed this effect. Any time she offered a numbered list, they would all write it down. If she had simply said, “Different genes, different environments, and experimental error,” most of them would have written nothing. Since she had first observed this syndrome, she included as many numbered lists as possible in her lectures.

She was a good teacher—somewhat to her surprise. In general, she felt her people skills were poor. She was impatient, and she could be abrasive, as she had been this morning with Sergeant Delaware. But she was a good communicator, clear and precise, and she enjoyed explaining things. There was nothing better than the kick of seeing enlightenment dawn in a student’s face.

“We can express this as an equation,” she said, and she turned around and wrote on the board with a stick of chalk:

Vt=Vg+Ve+Vm

    “Vt being the total variance, Vg the genetic component, Ve the environmental, and Vm the measurement error.” They all wrote down the equation. “The same may be applied to any measurable difference between human beings, from their height and weight to their tendency to believe in God. Can anyone here find fault with this?” No one spoke, so she gave them a clue. “The sum may be greater than the parts. But why?”

One of the young men spoke up. It was usually the men; the women were irritatingly shy. “Because genes and the environment act upon one another to multiply effects?”

“Exactly. Your genes steer you toward certain environmental experiences and away from others. Babies with different temperaments elicit different treatment from their parents. Active toddlers have different experiences than sedentary ones, even in the same house. Daredevil adolescents take more drugs than choirboys in the same town. We must add to the right-hand side of the equation the term Cge, meaning gene-environment covariation.” She wrote it on the board then looked at the Swiss Army watch on her wrist. It was five to four. “Any questions?”

For a change it was a woman who spoke up. She was Donna-Marie Dickson, a nurse who had gone back to school in her thirties, bright but shy. She said: “What about the Osmonds?”

The class laughed, and the woman blushed. Jeannie said gently: “Explain what you mean, Donna-Marie. Some of the class may be too young to remember the Osmonds.”

“They were a pop group in the seventies, all brothers and sisters. The Osmond family are all musical. But they don’t have the same genes, they’re not twins. It seems to have been the family environment that made them all musicians. Same with the Jackson Five.” The others, who were mostly younger, laughed again, and the woman smiled bashfully and added: “I’m giving away my age here.”

“Ms. Dickson makes an important point, and I’m surprised no one else thought of it,” Jeannie said. She was not surprised at all, but Donna-Marie needed to have her confidence boosted. “Charismatic and dedicated parents may make all their children conform to a certain ideal, regardless of their genes, just as abusive parents may turn out a whole family of schizophrenics. But these are extreme cases. A malnourished child will be short in stature, even if its parents and grandparents are all tall. An overfed child will be fat even if it has thin ancestors. Nevertheless, every new study tends to show, more conclusively than the last, that it is predominantly the genetic inheritance, rather than the environment or style of upbringing, that determines the nature of the child.” She paused. “If there are no more questions, please read Bouchard et al. in Science, 12 October 1990, before next Monday.” Jeannie picked up her papers.

They began packing up their books. She hung around for a few moments, to create an opportunity for students too timid to ask questions in open class to approach her privately. Introverts often became great scientists.