Last week
a man died of a heart attack while hooked up to an EEG. The parts of his brain associated with concentration, memory and dreaming all fired up while his heart was failing, and stayed fired up for about half a minute after it stopped beating. To all appearances, his life was flashing before his comatose eyes. An interesting thing to see, but a bit tricky to reproduce on other dying people to see if it's common among humans.
It turns out we don't have to. Back in 2013, 9 dying rats were hooked up to EKGs, and we saw that for half a minute after they 'died' their brains were extremely active; and that the sort of waves we saw are the kind associated with consciousness in humans. Now this opens up the intriguing possibility of testing any other primate besides a human; and if we see the same thing, then we know that it's common in every descendant of the ancestor of all primates and rodents (the odds of it independently evolving in humans and rats after that point not being worth discussing).
But now that we're diving down the cladogram, why stop there? We can finesse an amazing amount of research by running our first test on some farm raised salmon as they're being slaughtered. If we see it there, then we know that all the descendants of the first animal to evolve bones can be expected to have this happen when they die. And if not, we can work our way up the cladogram until we do find the first common ancestor that this occurred in.
Though to me, what would be the most interesting finding (if it actually happens) would be finding this in the brain of hagfish. Our last common ancestor with them is the first animal to evolve a spine. That would mean that every chordate from that time on had that happen to them when they died. Which would be fascinating.
But even if not. Even if the trait only shows up in the common ancestor of the rodents and the primates, it still leaves an intriguing question: what good does it do? How does the behavior of dying brains promote reproductive success? Or is this just an inevitable side effect of something else that is useful? I'm rather curious to see what they work out on that one.