Do you believe everyone shares a common humanity?

Yeah. I use the life cycle as evidence. Everything has its place, even spiders but it isn't just people. Every death equals a birth and everything dies/lives the same way. Also feels pain the same way. It could be meaningful I suppose.. but could be meaningless too, that's all a matter of perception.

Sure, and most of the time it's irrelevant. Octopuses ultimately burn oxygen too, but what the fuck is that supposed to mean to me?

No.