That British Amateur Naturalist had it all Wrong

[Centurion1]

but what if weaker genetic material survives and reproduces?

No it doesn't, war is actually beneficial to reproduction of the strongest.

Yes, the best usually ends up dead. But who cares? Because of their status as ideal genes they've already found a partner and reproduced themselves. Whether they're still alive beyond that point is irrelevant.

not necessarily. Especially in western society most young men (18) are not married and have not reproduced yet. and im sorry to say many of the weaker men are then given desk jobs because they cannot fight. They rarely die. The stronger ones are left to be front line combat troops and in that position they have a higher chance of being killed before they can reproduce and pass on their genes.

Myth. People are actually just as tall as they ever were and could be genetically. It's just more stable diets have allowed us to grow to our maximum height.

True i didn't even think about it, like the difference between the mongol invader compared to the average chinese.