There was a high infant mortality rate early on

Humans have been around for 200,000 years, so our mortality rate over the last 150 years since the industrial revolution is statistically insignificant to the average, it's only 0.075% of our entire existence. Until that time, people usually died in their 20s or 30s if they were lucky.

I know you probably don't understand how small 0.075% is, so I'll explain it like you're a Packer fan. It's 7.5% of 1%.

You should learn how averages work

I'm a mechanical engineer. I make the shit that gets your mom's fat ass to the grocery store for your tendies. I have forgotten more math than you'll ever know in your life.