No... That's not true. You're off by over one hundred years for the Western world. The UK passed the Cruelty to Animals act in 1876

https://en.wikipedia.org/wiki/Cruelty_to_Animals_Act,_1876

The act states that:

> "Researchers would be prosecuted for cruelty, unless they conformed to its provisions, which required that an experiment involving the infliction of pain upon animals to only be conducted when "the proposed experiments are absolutely necessary for the due instruction of the persons [so they may go on to use the instruction] to save or prolong human life"

It also contains punishments for not giving animals anesthestia, which is a ridiculous waste of resources if "people didn't even think animals felt pain until the 1980s."

Similar timeline on babies. But I think it's important to distinguish "scientists" from "people" in this case. My mom witnessed my brother's circumcision, on the day of his birth. She knew without a doubt that he was in immense pain, which the doctor flatly denied. Similarly, people who work with animals have known that they feel pain since time immemorial.

https://en.m.wikipedia.org/wiki/Pain_in_babies

This is one of these things that most people who deal with animals (so - almost everybody) knew for millenia but philosophers debated over cause it's interesting and you can show off how smart you are and quote classics.

You will have a very hard time taming an animal if you think it feels no pain.