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researchers studied the medical records of individuals who had gestated (were growing in their mothers’ uteruses) during the famine, noting any statistical abnormalities between them and other Dutch nationals who had not been so affected. The results were fascinating. Children whose mothers had been malnourished during the first trimester of their pregnancy were unusually likely to suffer from spina bifida,[5] cerebral palsy, and other conditions of the central nervous system. Additionally, girls from that cohort were twice as likely as the general population to develop schizophrenia. Clearly, malnutrition during those first few months of development impinges on the brain’s ability to properly develop.

      However, perhaps the most surprising finding involved men born to mothers who had been malnourished during the first two trimesters of their pregnancy. A 1976 study found that these men, now in their thirties, were significantly more likely to be obese than other men of their age and background whose mothers had not experienced the Hunger Winter. Further studies, though performed on rats instead of people, have helped us to understand the mechanism behind this strange phenomenon. Mothers’ malnutrition during the first two trimesters of pregnancy leads to unusually high insulin levels in male fetuses during the third trimester, which can affect the development of the fetus’ brain. We don’t yet know for sure why this occurs, and why it doesn’t affect females, but it does make sense from an evolutionary standpoint. Mothers experiencing famine could be hormonally conditioning their children’s metabolism to most effectively function in an environment where sources of nutrition are scarce. If a child is born into an environment plagued by famine, the ability to readily store fat would be a significant advantage. However, once the boys were born and the problem of food scarcity was solved, they nevertheless retained their prenatal conditioning despite the fact that their evolutionary advantage had become a disadvantage.

      The Hunger Winter provides a good example of how environmental influences on development can easily remain buried beneath the surface of human development, only to be unearthed generations later by a dramatic change in the landscape. Had the Hunger Winter not occurred, we may never have learned that the prenatal environment can affect an individual’s propensity to store fat, and the men studied would likely have developed a body type similar to those of their relatives (though, as always, diet and exercise would have played an important part).

      Admittedly, the Hunger Winter is an extreme example. Under normal circumstances, attributing environmental influence to height or hair colour may seem unnecessarily pedantic. After all, if the environmental factor contributing to a trait’s development is present everywhere on Earth, isn’t it fair to say that said trait is genetically determined? If someone’s genetic makeup dictates they will have green eyes, they’re almost certainly going to get them, whether they live on the streets of inner-city Baltimore or in a mansion in Beverly Hills. Likewise, for certain conditions, a single aberrant gene really is the root cause. One could reasonably argue that calling CFTR[6] “the gene for cystic fibrosis” is accurate shorthand, as cystic fibrosis occurs when an individual inherits two mutated versions of that specific gene. The environment in which the affected child is raised will not alter how the gene behaves.

      Nevertheless, relying on terms like “the gene for X” can be dangerously reductive, as it blinkers our thinking and encourages limited, simplistic approaches to complex problems.

      Let’s consider the scene that began this chapter. Remember Thomas? Was his facility with the guitar purely the result of his genes? It would be difficult to argue that environmental influence didn’t play some part. No one picks up an instrument and plays Bach on the first try. It takes hours and hours of practice to develop the requisite agility, finger strength, and muscle memory. Despite what anyone with particularly accomplished parents may hope, skills and knowledge do not come prepackaged inside our chromosomes. Bodybuilders do not sire toned, muscular children, nor do the offspring of computer programmers enter the world knowing how to code in C++. Every generation must develop these skills from scratch.

      Okay, so Thomas’s talent was tempered by hours of dedicated study. But what about Amelia? An instrument may require extensive experience to be played competently, but some people are blessed with a natural singing voice. Amelia’s father, we are told, is an excellent singer, and so too are most of his immediate family. It stands to reason that their musical aptitude was passed down through the generations. Thomas had to work to develop his skills, but Amelia was simply fortunate enough to inherit a gift. Right?

      Genetically speaking, it is possible that Amelia was born with certain traits advantageous to a burgeoning singer. If her father’s family has truly abounded with talented vocalists throughout the generations, then perhaps their genes code for better-than-average lung capacity, a strong diaphragm, or exceptionally dexterous vocal cords, and these predispositions are what drew her ancestors to singing in the first place. This could be the case, but to assume it must be — and to cite Amelia’s proclivities as the only evidence — is tremendously naive. It is equally possible, perhaps even probable, that Amelia possesses no physiological advantage as a singer whatsoever. Half her genes come from her mother, after all, who readily admits that her whole family is tin-eared and musically inept. This is not to say that Amelia’s talent wasn’t inherited, only that we mustn’t limit our idea of inheritance to a transaction involving a few dozen molecules.

      If Amelia is from a musical home, she probably grew up with music as an important part of her life. We can assume the record player was running often, and that her father regularly sang around the house. In this case, her musical education began before she was even born.

      Children develop an aural connection with the outside world as early as six months after conception. Researchers recruited a group of pregnant women and had them read one of two stories — The Cat in the Hat or The King, the Mice, and the Cheese — aloud twice a day from the time they were seven months pregnant until the day they gave birth. Two days after they were born, the children of these mothers were tested to see which story they preferred, using a fairly ingenious device that measured how often they sucked on a pacifier. Sucking is a reflex ingrained in children from birth, and one of the few motions over which infants have conscious (or close to conscious) control. By adjusting the speed of their sucking, the babies could choose whether they heard a recording of The Cat in the Hat or The King, the Mice, and the Cheese. Infants consistently preferred to hear recordings of whichever story their mothers had read aloud while they were in the womb. More fascinating still, researchers achieved the same result even if the recording was not of the child’s mother reading, but a total stranger. This means the children were not simply responding to the unique vocal register of their mothers, but to the specific cadence of the story itself.

      Conceivably, then, if Amelia’s father played a variety of music around the house during her gestation, she would have become familiar with the notions of melody, harmony, and counterpoint before she had even drawn her first breath. This is not to say she would have been composing symphonies in her crib, but repeated listening would have attuned her ear to the pitches and intervals common in Western music. Perhaps just as importantly, she would have developed a positive association with the songs she heard in utero, making it that much more likely she would take to music as a child.

      As Amelia grew, her musical upbringing would have continued to influence her behaviour. There would have been musical scores lying around for her to ponder, tapes and CDs for her to listen to, and instruments for her to tinker with. And even if her father was not the type of man to force his child to follow in his footsteps, he would almost certainly have encouraged any interest in music that Amelia displayed. After all, what parent wouldn’t want their child to feel passionate about the same things they do?

      We inherit more from our parents than our chromosomes. They are the ones who teach us, feed us, scold us when we misbehave, and console us when we scrape our knees or embarrass ourselves at school. They are responsible for cultivating the environments in which we are raised. We are as much the beneficiaries of their affluence (or lack thereof), their dispositions, and their teachings as we are of their genes.

      Of course, none of Amelia’s hypothetical early training can guarantee that she will become a musical prodigy. Innate ability does exist, and there are limits to the extent that environmental factors can sculpt an individual. They can chisel out a form, but the genetic material from which the subject is carved will inevitably

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