“The apple doesn’t fall far from the tree”.

“Chip off the old block”.

“Cut from the same cloth”.

“Black cat, black kitten”.

“Chickens don’t make ducks”.

“He didn’t lick it off the stones”.

“It’s not from the wind she got it”.

“She comes by it honestly”.





Every culture seems to have its own phrases describing the power of heredity – not just for physical traits, but also for behavioural ones. (Those last three are peculiar to Ireland, I think). This folk wisdom, accumulated from centuries of observation of human behaviour, seems to reflect a widespread belief that genetic effects on behaviour and personality are strong, indeed dominant over effects of upbringing.





(Image credit: https://schoolworkhelper.net/essay-nature-vs-nurture-or-both/)





Of course, folk wisdom can be wrong. And old folk sayings may not reflect current thinking – perhaps people’s opinions on the subject have changed. Indeed, if you were to take academic discourse on the subject as a barometer of views of the general public, you might think that many people ascribe no power to nature at all and most or all of it to nurture instead. Those debates do not remain within the walls of the academy – we see them played out in social policies on education, early intervention, in the criminal justice system, in psychiatric practice and other arenas.





So, do those folk sayings accurately reflect public opinion on the power of nature over nurture? Well, the easiest way to find out would be to just ask a bunch of people. However, while there are lots of surveys of people’s attitudes towards genetic testing or screening (such as here and here ), I was unable to find any on more general beliefs about heredity, especially of psychological or behavioural traits. (If dear readers know of any, please let me know).





However, there is one area where these beliefs are directly tested, which is in assisted reproduction, especially where it involves sperm or egg donors. In many cases, couples can choose sperm or egg donors on the basis of any number of characteristics, which prominently include things like intelligence, educational attainment, musical talent, and general personality traits, in addition to physical characteristics like height, body-mass index, athleticism, and general health. Clearly, an interest in the psychological traits of potential donors reflects an underlying belief in the heritability of such traits.





This was thrown into stark relief by a case from 2016 that received a lot of media attention. A couple had selected a sperm donor on the basis of a profile in which he claimed to have an IQ of 160, a bachelor’s degree in neuroscience, a master’s in artificial intelligence and to be studying for a PhD in neural engineering. They found out later that he was a college dropout, with a criminal record, having served time in prison for burglary, and that he had been diagnosed with schizophrenia and narcissistic personality disorder. (More details of his story emerged later but the important thing for this discussion is this initial presentation).





This donor’s sperm had been used to father 36 babies. The couple in question had selected him because his high intelligence and even his scientific interests matched one of the couple. On learning of his actual profile, they described it as “A dream turned nightmare in an instant”. They went on to say: “ In hindsight, a hitchhiker on the side of the road would have been a far more responsible option for conceiving a child.”





This story received a lot of media attention, in newspaper articles, online magazines, and on radio and television. All of these stories played up the horror of the couple in question and the outrageousness of the deceit that had been perpetrated on them. What struck me at the time, though, in almost all of the coverage I saw, was that no one questioned whether this couple, and others who had children using this donor’s sperm, were right to be horrified. It was taken for granted that the traits of the donor would indeed have a significant impact on the trait’s of the offspring.





None of the commentators argued that mental illnesses like schizophrenia were really caused by cold parenting, childhood experiences, or environmental factors. The common wisdom was clearly that mental illness runs in families and that having a father with schizophrenia greatly increased the risk of this highly debilitating and often devastating disorder in the offspring. (And, of course, this is absolutely true).





Similarly, no one claimed that all children are born with equal intellectual potential, that eventual differences in intelligence solely reflect differences in education or societal factors, or that IQ tests only measure how good you are at taking IQ tests. The understanding that intelligence is real, important, and substantially heritable was so implicit that it never came up. (And, of course, this is true too, at least that genetic differences make a major contribution to relative differences in intelligence between people – though education and other factors affect the absolute levels that any individual attains).





When talking about these things in the abstract or in general terms across the population, many people may espouse a view that weights nurture more heavily than nature. But when the rubber meets the road, when people are making choices that they feel may directly and possibly profoundly affect their children, they clearly place a heavy emphasis on the power of heredity. And most neutral commentators seem to think that view is so reasonable that it doesn’t even occur to them to comment on it, never mind question it.





People looking for sperm or egg donors clearly prefer those with certain traits and without others. Now, you might say they’re just hedging their bets. If there is an option to choose donors with traits deemed more desirable, then they might as well, whether they strongly believe they are heritable or not. If they’re not really heritable, there’s no harm done. But it goes beyond just exercising that choice – people are willing to pay extra for donors with more desirable traits. (I’m not arguing here that some traits should be seen as more or less desirable – just that the “consumers” in this scenario see them as such).





Gamete donation is big business. This is especially true for egg donors, because eggs are much more difficult and expensive to collect than sperm and there are both far fewer willing donors and far fewer actual eggs. This is a strangely unregulated market, especially in the United States. The American Society for Reproductive Medicine has ethical guidelines that propose a cap on how much women should be paid for their eggs ($10,000), but most fertility agencies operate outside the medical establishment and many ignore this guideline . The legality of the ASRM’s position has been challenged by a number of women, given the overall amounts of money that such agencies can make from clients and the very high value that some women can demand for their eggs on the open market. (See here for a personal story of how this kind of interaction can play out).





confidence attached to the idea that they are really heritable. If people didn’t think a trait like intelligence was largely heritable, they wouldn’t pay for more intelligent donors, no matter how much they value the trait. Clearly, they think it is, as there are agencies specifically marketing educational attainment as one of the main selling points of the egg donors from whom prospective parents can choose. Musical and artistic abilities are also much sought after and many descriptors of donors include all kinds of other personality traits and lifestyle descriptors that seem to be of interest to clients. The willingness of prospective parents to pay for desirable traits indicates both the value attached to such traits as well as theattached to the idea that they are really heritable. If people didn’t think a trait like intelligence was largely heritable, they wouldn’t pay for more intelligent donors, no matter how much they value the trait. Clearly, they think it is, as there are agencies specifically marketing educational attainment as one of the main selling points of the egg donors from whom prospective parents can choose. Musical and artistic abilities are also much sought after and many descriptors of donors include all kinds of other personality traits and lifestyle descriptors that seem to be of interest to clients.





For example, the Egg Donor Program “ markets itself as an exclusive club where selected donors are referred to as “Premier Donor Angels: beautiful, accomplished, highly educated” ( www.eggdonation.com )”.









The Donor Concierge agency promises intelligent donors, students in or graduates of Ivy League universities, with a minimum grade point average.





So, if we take donor selection as the ultimate test-bed of people’s true beliefs on heredity – where they literally put their money where their mouth is – it certainly seems that the folk sayings referred to above do accurately reflect beliefs about psychological traits. (At least among the admittedly non-random set of people who undertake this kind of assisted reproduction). Beliefs about the heritability of intelligence or of mental illness are, in fact, well founded and match our current scientific understanding. Beliefs about other psychological traits probably substantially overestimate the importance of genetic effects.





One final note: it seems inevitable that the market in egg and sperm donation will soon incorporate molecular genetic profiling and trait prediction. The direct to consumer genomics company 23andMe had a patent granted in 2008 for what they called their “Inheritance Calculator”, which would enable people to predict traits of offspring from genotyped parents or donors. The backlash against the idea led the company to state that they had “no plans to pursue the idea”.





However, another company, GenePeeks, Inc., was established precisely for the purpose of molecularly genotyping potential donors , though it is currently only aimed at predicting possible rare diseases in offspring between clients and donors. It seems a small step to include other non-medical traits of interest, however, especially if they can be accurately predicted from polygenic profiles. Currently, things like intelligence cannot be accurately predicted for an individual, but it may be possible to generate comparative scores that would influence donor selection. The new company Genomic Prediction, Inc., aims to use polygenic profiles to predict risk for complex disorders – the same approach could certainly be used for many non-medical traits.





Whatever one thinks about the ethics of this kind of consumer-driven eugenics , it clearly is only going to increase. The lay understanding of genetics and heredity is thus already a factor in the market of assisted reproduction and seems likely to grow in importance over the coming years.



