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“What”, asks clinical psychologist Oliver James, “would lead to acceptance of the null hypothesis of the Human Genome Project as regards psychological traits?”.
The answer to this question is “a scientific literature that looks very different indeed to the existing one”. In his letter, James exploits the complex nature of behavior genetics to sow confusion about what geneticists have found. In an attempt to clear up some of that confusion, below is a point-by-point rebuttal to each one of his arguments.
James: “The hypothesis of the Human Genome Project (HGP) was that differences in DNA sequences would significantly explain why one individual is more likely to possess a trait than another. This has been proven to be true for some physical differences, such as anatomical ones, like height. But, so far, there are no psychological traits – none at all – which have been shown to be significantly influenced by specific variations in DNA (James, 2016).”
It is very odd to concede that genes influence height, but then deny that the same is true for psychological traits, because the evidence for both inferences comes from exactly the same scientific methodology. All kinds of behaviour-genetic investigations (twin studies, family pedigree studies, adoption studies, and newer DNA-based studies) show consistent results when it comes to height and to psychological traits such as IQ, personality, and many other psychological measures. Physical and psychological traits are both under substantial genetic influence. I will get to James’s statement about “specific variations in DNA” below.
Read full, original post: Jump the gun and you will be shot down
