Sunset
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
Well, the animals and plants are different. And humans need specific nutrition to be healthy and being able to carry babies to term.
Or maybe there is a specific disease that kills off all pregnancies unless a whole village collaborates to prevent a human from temporarily being affected by it.
Think Zika virus that can only be countered by eating a very rare plant that needs to be prepared in a specific way to preserve the anti-viral properties?
Or that there is no anti-viral solution, so they resort to manual methods of protecting the individual for first X amount of time, which would be a real challenge in a non-industrial society.