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> A lot of the lower life expectancy was sky-high infant mortality If that was true, then age composition would be roughly the same as is now, except for large

• ksaj 5y ago
  The weakness in that argument is that it presupposes childhood health indicators and adult health indicators are linear, which we know to not be the case. For example, the introduction and "ramping up" of testosterone and estrogen at puberty has a significant impact on the human condition that simply cannot apply to the prepubescent state, as does their subsequent decline in menopause and old age in general. Each stage of life comes with its own signals that can be serious health conditions if present in other stages of life, but completely normal and healthy at the appropriate stage. A tween with acne is rarely something to call the doctor about. But a 3 year old with acne certainly is. A colicky baby needs a soother or some other placation. But a colicky adult certainly needs medical intervention. So the idea that weak babies make weak adults and strong babies make strong adults doesn't work out as cleanly as this comment suggests.