Seeing as how we hunted multiple mega fauna to extinction, I'm gonna go ahead and say that humans have been eating meat for a very long time. Also there's shit tons of archeological evidence for our omnivorous diet going back hundreds of thousands of years, but... whatever.

I will never understand why people feel the need to try and prove humans are supposed to be herbivores. Who gives a fuck? There's ample evidence that your can eat a healthy vegan diet, who gives a shit about "supposed to" if you can eat vegan either way?