system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did humanity survive millennia of smoking and drinking during pregnancy if they are bad for fetuses?
gpt
Smoking may not be as old as you think. It was around, but it wasn't something everybody did. Certain cultures incorporated smoking into their rituals. The idea that smoking was something people would just *do* for the hell of it didn't become popular in Europe until after the Americas were 'discovered'.

> If drinking and smoking was considered safe for millennia

Safety, in the sense you are using it, is another relatively recent idea.

150 years ago people didn't know about *germs*. They had ideas about what was or was not *healthy* - usually wrong ideas, like bloodletting and miasma theory and 'humours', but they were at least thinking about it - but aside from things like "it's not safe to eat poisonous mushrooms", they weren't thinking of things in terms of safety.

We only figured out what genes do in the late 1800s. And less than a hundred years ago, miscarriages and stillbirths were often the *norm*... they still are, in some places. We've only known about *sperm* for 400 years or so, and until we had good microscopes we thought each one contained a tiny human that, once 'planted' in a woman, would grow to baby size. We didn't have an understanding of how the mother's health or genes affected the fetus until the last century or so.

There were just too many dots not yet connected between those things and the idea that what a pregnant woman ate or was otherwise exposed to could possibly harm the fetus. It wasn't something people thought about, because they didn't have a framework or context to think about it.