Seems to be getting a few down votes. No one likes to be called dumb. But I do think its an issue worth exploring. I think he’s underestimating the IQ of irish by a few points, I see 95 to 97 in a few places. Alcoholism and extreme poverty/ malnutrition might have kept them down for a few centuries under the british potato regime. But I think thats been corrected for in the last 50 years or so and the micks are still a few points down compared to the english. I could not find a number for welsh IQ or Cornish IQ but Scottish IQ seems to be about 97 which sounds about right, i.e. similar to the Irish. I believe he’s making too much of a distinction between Q celts and P celts. They were largely the same gang of people conquering and intermarrying with the local older populations. I know a little about successive european migrations, maybe not enough to speak too definitively. But it seems to me ireland and britain have almost all the same founding populations only in slightly different proportions. Britons have plenty of that pre-indoeuropean stock he’s referring to. SE England seems to have a bit more germanic DNA. The english are essentially germanic-welsh rape babies, which seems to have given them a little edge. But maybe more importantly than any of these origin stories is in fact the pressures of the last 2000 years or so. I do think things like the black plague could have been influential. Also catholicism and non reproducing priestly casts. Perhaps the celtic clann political structure was too egalitarian? Perhaps the germanics culled a lot of the weaklings when they invaded the brithonics? Perhaps the fact that britain was more populated made britons subjected to more competition?