Generations of data, fewer differences in environmental factors between members (diets, lifestyle, diseases, etc) to obscure the effect. For long-term effects like this, ‘modern science’ hasn’t really existed long enough to get much data in comparison to centuries of generational trial-and-error
Edit: also, long-term effects measured now have a bunch of confounders due to lifestyle change and rapid technological and medical development, while their conditions were basically stationary. Scientists would kill for that kind of data now!
Generations of data, fewer differences in environmental factors between members (diets, lifestyle, diseases, etc) to obscure the effect. For long-term effects like this, ‘modern science’ hasn’t really existed long enough to get much data in comparison to centuries of generational trial-and-error
Edit: also, long-term effects measured now have a bunch of confounders due to lifestyle change and rapid technological and medical development, while their conditions were basically stationary. Scientists would kill for that kind of data now!