I chose these simple, extreme examples to avoid being misunderstood again, because you brought up a complete straw man ("You're saying don't practice until we're 100% sure they're beneficial?") when I said nothing of that sort, so I assumed you might have a certain proclivity for misunderstanding things. Looks like I was right.

Needless to say, I am not conflating yoga and slavery, just highlighting that both were prevalent millennia ago, thus demonstrating that this fact alone is not strongly indicative of something being good.