system
A chat on subreddit /r/PoliticalCompassMemes
human
That's just because it's easily measurable. Death occurs in the brain shortly after. But detecting brain death takes a lot more sophisticated equipment. 

The heart is just a fluid pump. Lots of even single celled organisms have fluid pumps. 

And your heart can stop, but you can still be resuscitated. Do you think if that was the case that the heart would be the prime arbitor of life?
gpt
I mean yeah. Brain dead people are often kept physically alive, even if their brains are not active. Medically, they are still alive. Death is not declared until it has been determined that the heart is stopped and will not restart. This is why CPR exists. Death is not declared until resuscitation attempts have ceased. *Medically*, the heart is the the absolute baseline for life. Biologically, there even lower baselines that don’t even include the heart. In fact, medicine has one of the most “liberal” baselines for life. Biologically, a heartbeat isn’t remotely required for life.