Comment by orwin

Since pretty much the beginning of agriculture until very recently (and with some localized exceptions on some coastlines, depending on the available fishes), fatty acid just werent available. "Margarine" isn't coming from nowhere, and it is _very_ telling that it was "invented" (or rather, re-discovered) during the first industrial revolution. A vegetarian today will eat overall more saturated fat and animal proteins than the vast majority of people in agrarian societies pre-1950.

Over way more generations.

In any case, i think its the reverse actually. Plants bio-accumulate way, way less than animals, and eating to much fish or meat leads to issues with lead accumulation, or hormonal imbalance (which is less of an issue in europe, since we don't allow growth hormones in our meat). Since animal protein are sightly more bio-available, i also think vegans are foolish, and the truth is clearly in the middle, and you should eat both animal and vegetal proteins (as long as you don't follow the US government guideline on protein intake: the values are what my sister recommended for semi-pro athletes when she worked as a nutritionist).