Hitler DNA analysis sparks reflection on what our genes say about us: Garth Zietsman

Key topics:Media reaction to claims about Hitler’s genetics and mental-health risksLimits of polygenic scores and misconceptions about “genes vs environment”Adult outcomes shaped mostly by genetics; upbringing effects minimal.Sign up for your early morning brew of the BizNews Insider to keep you up to speed with the content that matters. The newsletter will land in your inbox at 5:30am weekdays. Register here.Support South Africa’s bastion of independent journalism, offering balanced insights on investments, business, and the political economy, by joining BizNews Premium. Register here.If you prefer WhatsApp for updates, sign up to the BizNews channel here..By Garth Zietsman*.An analysis of Adolf Hitler’s DNA made a splash in the media last week, and of course that intrigued many people but also caused a cautionary reaction.The scientists who did the work mentioned a few interesting results. Firstly, they put to rest the myth that Hitler has Jewish ancestry. He did not. They said Hitler had a genetic condition, Kallmann syndrome, that delays puberty i.e., prevents testes descending normally, confirming a medical report from his time in jail. They also said he carried a high genetic risk for schizophrenia, autism, ADHD and bipolar disorder each exceeding 99% of the population.They could have provided many more interesting polygenic scores, like for his IQ or ultimate years of education, other personality dimensions, and so on.As is always the case with the genetic basis of anything, there was the predictable backlash by interested commentators. Most of the complaints had to do with the implied suggestion that Hitler had those mental illnesses.The claim is that this suggestion exposes people who have those mental problems to an unfair comparison to history’s quintessential monster. A number of experts felt bound to point out that genes are not destiny, and a genetic risk does not mean the person who carries it always goes on to develop it.A polygenic score is a weighted count of all those gene variations associated with a particular trait such as height. It allows the calculation of an individual’s probability of developing the trait, such as being 2m tall. It is certainly correct that genes are not destiny but that is also a bit misleading.The claim that genes are not destiny partly leans on a counterclaim that our environment, and perhaps our free will, can override our genes. They give the subtle sense that this is even the most likely scenario. This is what is misleading. The influence of genes associated with a trait is the heritability of the trait. If height is heritable then large differences in genes will be associated with large differences in height.People who are closely related should have fewer genetic differences, so if height is heritable, they should also show smaller differences in height than is true on average. For example, the height of siblings (same sex and age) may differ by 2cm on average but in the general population the average height difference between random people might be 5cm. The heritability of height is the percentage of the variation in height in a population explained by the genetic variation in the population..Variation of a trait.The variation of a trait not explained by genetic variation divides up into the variation explained by environmental differences between families, the variation explained by environmental differences within families, and random errors of measurement. Between-family differences are those non-genetic factors shared by all family members but not members of other families. Examples include socio-economic status, child rearing practices, number of books in the home, typical diets, church denomination, etc.Most people think these are the factors that through manipulation can change behaviours and outcomes. The hypothesized factors and the proposed manipulation often become political. Within-family differences are those which are different across siblings, such as experiences you had but your brother did not. Examples include infections, accidents, friends and so on.Almost everything about humans is heritable to some extent, including intelligence, personality, political preference, religiosity, conscientiousness, individualism-collectivism and even attitudes. Some of these as much as 80% but usually personality, character and attitude are about 50% heritable. So, if these traits are only 50% heritable then the other 50% must be environmental influences, which means we can counteract the influence of genes, right?This is where things become misleading. Firstly, the same research that discovered these traits are 50% heritable also routinely find that by the time we are adults the influence of between-family environmental influence is effectively zero..Little to no effect.That means child-raising practices, more money or extra education, things usually believed to make a difference, have little to no effect on how you turn out. Freud’s theories, and notions of systemic prejudice or neglect, as explanations of differences in how we turn out, must be wrong. Secondly, while the remaining environmental factors do cause differences, we have no idea what those factors are, other than they operate within families or randomly on individuals.What we are is genes and we don’t know. In other words, a polygenic score will tell you the genetically based probability of various traits, but you will not know what you can do to modify that probability. The expert commentators on Hitler’s DNA analysis are misleading when they imply you can override a genetic risk.At best we can say it may not come to be and calculate that probability. Scientists have only identified the genes for about one third of the genetic effect we know is there, so the probability predictions are quite low. Although Hitler’s polygenic risk is higher than 99% of people that does not translate into a risk of 99%.If the heritability is 50%, and the polygenic score only accounts for a third of that, then his risk was more like 16%. In the near future we may discover what within-family environmental factors do make a difference e.g., an infection that switches on the genetic risk to schizophrenia. That may give us the means to control the outcome.None of the expert commentators mention this but schizophrenia-, ADHD-, autism- and mania-related genes are not only negative. A mild level of schizophrenia is associated with outstanding creativity, ADHD and autism with intense focus, and manic traits will high energy..What and who we are.Our genes, in tandem with unknown environmental factors, do determine what and who we are.However, our current ability to predict outcomes from our genes is quite limited, particularly if they depend on many genes, so don’t put much weight on what they imply. Also, the negative things associated with genes often come along with good things.Finally, ignore the politics around your upbringing or your socio-economic status. They play almost no role in how anyone turns out..*Garth Zietsman is a professional statistician with 40 years’ experience applying his skills to social, medical and economic issues..*This article was originally published by Daily Friend and has been republished with permission.

Hitler DNA analysis sparks reflection on what our genes say about us: Garth Zietsman

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