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This wouldn't work for "longevity" because "longevity" isn't a bell curve. If "longevity" were a bell curve, we would see some humans at the 150 years old mark

by bsder 5y ago

This wouldn't work for "longevity" because "longevity" isn't a bell curve. If "longevity" were a bell curve, we would see some humans at the 150 years old mark. We do not. Human longevity has a "cliff" that it won't go past. Selective breeding could get you arbitrarily close to whatever that cliff actually is, but no further. To get further than that cliff, you would have to fix all the issues that cause it. There is no guarantee (and practically an anti-guarantee) that selective breeding would ever accomplish that.

setr 5y ago
> If "longevity" were a bell curve, we would see some humans at the 150 years old mark. We do not. I agree with everything else (including that its not a bell curve), but this particular reasoning seems off — it could still follow a bell curve even if we never see the rarer items… because we’re only talking about approximating a bell curve. Just as height’s bell curve suggests a 30ft human could eventually occur, but we’d never actually expect it to actually happen in reality (because confounding factors will start to trigger) - but we still say height follows a bell curve.
- bsder 5y ago
  No, the bell curve for height does not suggest a 30ft human would ever occur. That would be somewhere around 90+ standard deviations out--that's so wildly improbable as to be effectively 0. A "mere" 7 standard deviations is effectively 1 in a billion. And that's somewhere around a 7 1/2 foot tall human (who we do see occasionally). "Standard deviation of lifespan" (a somewhat erroneous idea since we're not actually on a bell curve) is somewhere around 10 years. 150 years old is 7 standard deviations--improbable but not impossible. If we're following a bell curve, 1 in a billion people should be 140 years+ and 1 in 10,000 should be 120 years+. The fact that we don't see these probabilities is extremely strong evidence we're not on a bell curve. And not being on a bell curve immediately throws out huge chunks of statistical "rules".

by bsder 5y ago

setr 5y ago

> If "longevity" were a bell curve, we would see some humans at the 150 years old mark. We do not. I agree with everything else (including that its not a bell curve), but this particular reasoning seems off — it could still follow a bell curve even if we never see the rarer items… because we’re only talking about approximating a bell curve. Just as height’s bell curve suggests a 30ft human could eventually occur, but we’d never actually expect it to actually happen in reality (because confounding factors will start to trigger) - but we still say height follows a bell curve.

bsder 5y ago
No, the bell curve for height does not suggest a 30ft human would ever occur. That would be somewhere around 90+ standard deviations out--that's so wildly improbable as to be effectively 0. A "mere" 7 standard deviations is effectively 1 in a billion. And that's somewhere around a 7 1/2 foot tall human (who we do see occasionally). "Standard deviation of lifespan" (a somewhat erroneous idea since we're not actually on a bell curve) is somewhere around 10 years. 150 years old is 7 standard deviations--improbable but not impossible. If we're following a bell curve, 1 in a billion people should be 140 years+ and 1 in 10,000 should be 120 years+. The fact that we don't see these probabilities is extremely strong evidence we're not on a bell curve. And not being on a bell curve immediately throws out huge chunks of statistical "rules".