10月12日 少々刺激的なネタがまな板に。「心」はＤＮＡ・遺伝が支配していると・・・。

DNA and Individual Difference — 99% the Same, Yet Uniquely You

Human DNA consists of three billion base pairs, and 99% of those are identical across all of humanity. The remaining 1%—roughly 30 million base pairs—accounts for every individual difference. Yet genes do not unilaterally dictate a life. What Dr. Robert Plomin calls 'DNA's whisper' is a collaborative process: at the moment a person makes a choice, the DNA that aligns with that choice switches on. Likes and dislikes are shaped by this mechanism, and their cumulative weight is what makes a person distinctively themselves.

Genetic Influence Grows with Age — from 20% in Early Childhood to 80% at 65

A 1983 study that tracked 500 pairs of twins over twenty years revealed a striking pattern: heritability rises sharply with age. In early childhood it stands at around 20%; in adolescence it climbs above 60%; and by age 65 it reaches 80%. Takeda Tetsuya (武田鉄矢) describes this as 'eighty percent of your older self resembling someone among your ancestors.' Parents contribute only 50% of a child's genes; the rest traces back through the full ancestral line, all the way to humanity's African origins. Small genetic nudges in childhood compound through environmental choices in a snowballing process Plomin calls 'genetic amplification.'

Why Elementary School Grades Lose Their Meaning After Middle School

In elementary school, academic performance is driven largely by the ability to read—to decode text—which is strongly shaped by parental influence. Children of avid readers tend to score well. But middle school shifts the demand to comprehension intelligence, and that is when the genetic switch for intelligence turns on. As the brain's neural networks expand, the heritability of intelligence surges, and children who dominated elementary school find themselves steadily overtaken by classmates. Takeda frames exams not as a tool for teachers to assign scores, but as a 'master-key search'—a way for children to discover which doors their particular key can open.

Same Family, Such Different Lives — the Mystery of the Clinton Brothers

Chapter 7 of Plomin's book asks why children raised in the same home can turn out so differently. The Clinton brothers offer the starkest illustration. Roger Clinton was known inside the White House as a 'good-for-nothing' and a 'headache,' eventually caught dealing and using drugs. Their parents gave both Bill and Roger the same politically oriented upbringing and made equal investments in both. Yet in adolescence, Bill's switch landed on 'I want to work for America' while Roger's landed on 'I want to profit from America.' That tiny divergence, replicated by chance three or four times over, produced a president on one side and a drug dealer on the other. Plomin's conclusion: the same coincidence cannot repeat identically through an entire childhood, so siblings inevitably diverge.

Genes Are Not Destiny but a 'Master Key' — and Behind Every Genius, a Touch of Madness

Takeda's recurring message is that genetics is not fate. Shohei Ohtani could only have been born to his parents, yet those same parents could never produce him again. The consoling cliché 'everyone can do it if they try hard enough' is, Takeda states flatly, a lie—and a harmful one, because it burdens children with blame for doors their key was never made to open. Genes are a master key; the wrong door should be abandoned, and finding the right door is what living is about.

Takeda draws on his own life: in college he encountered the poem 'Uta' (「歌」) by poet Nakano Shigeharu (中野茂春)—'Sing from the place where it barely feeds you'—and it ignited the defiant lyrical voice heard in songs like 'Anta ga Taisho' (「あんたが大将」). That, he says, was the moment his own genetic switch clicked on.

Plomin himself underwent genetic testing and found a high score for schizophrenia risk, yet that same predisposition correlates with exceptional creative thinking. Aristotle, Van Gogh, John Lennon, and Hemingway are said to share the tendency: genius and madness occupy the same genetic neighborhood. On Alzheimer's, roughly 10% of the population carries a risk gene, but the disease only develops when multiple environmental switches align simultaneously. Eliminating even one of those switches can reduce the risk—and on that note, the broadcast closed.