As they all sat at Francis’s kitchen table, loading blinis with toppling mounds of sour cream and caviar, Hunter somehow persuaded them that Lucy’s health was not the only reason to knock back a shot of vodka. His acquisition of the remaining shares of YouGenetics provoked another toast and, when he found out about Olivia’s old antagonism with Bill Moorhead, he insisted that they must raise a glass ‘To the downfall of pompous men and false friends!’

‘So, what are you writing your paper on, Olivia?’ asked Hunter.

‘Oh, I’m working on a paper about schizophrenia, with my father, Martin Carr. He’s a psychoanalyst. I’m looking into the genetics, while he’s writing up some case studies. And we’re also trying to get a neuroscientist on board.’

‘What’s the lowdown?’ said Hunter.

‘Well,’ said Olivia, ‘briefly, there’s an impressive list of environmental stresses correlated with schizophrenia: war, bullying, the early death of a parent, physical and sexual abuse, migration, deracination, racism, and so on. They’re strongly associated with schizophrenia on their own, or possibly in combination with a multitude of marginally implicated genes, but there’s no evidence that the genes on their own can cause schizophrenia. Also, even if genetic expressions are switched on or off by stresses, the results would still shed only a hazy light on the question of inheritability since many of the mutations in schizophrenics are “de novo”, occurring for the first time in that person and, therefore, by definition, not inherited.’

‘What about twin studies?’ said Hunter. ‘Aren’t they the gold standard for a lot of this genetic analysis?’

‘They’re often treated that way,’ said Olivia, ‘but lots of clinical psychologists, like my brother Charlie, question the Equal Environment Assumption on which they rest. They attribute outcomes to purely genetic causes by ignoring favouritism, scapegoating, imposed narratives and, in the case of identical twins, the effects of often being dressed in the same clothes, being in the same class at school, having the same friends, being mistaken for each other and experiencing “ego fusion”. Genetic enthusiasts try to get around these social and psychological facts by saying that the genes of identical twins “create” confounding non-genetic influences, as if two infant twins, lying next to each other in the same pram, cast out a powerful genetic force field that compels their mother to dress them identically, while the rest of the world turns to stone. The mother herself is not, in this persuasive scenario, subject to any environmental, financial, social or psychological forces, or indeed genetic influences of her own, but is just controlled by her monozygotic twins’ genetic “creativity”. It’s the kind of circular argument, assuming what it set out to prove, that appears again and again in twin studies, like a wagon formation protecting a beleaguered dogma.’