Let us imagine a nice elderly couple, spending their retirement travelling the galaxy observing wildlife.
Earth's one of their favourites but it's been a few centuries since they visited.
Pa: It says here there are now 7 billion humans, that's quite an impressive effort, we should have a little party to celebrate.
Ma: Are you sure?
Pa: Ye, let's make a guest list.
Ma: Oh, well OK, if you wan't.
Pa: Dodo, we must invite a dodo, remember those lovely birds.
Ma: Na, none left.
Pa: What, what happened?
Ma: Humans ate them all.
Pa: Ah well, there never were many of them though.
How about a few passenger pigeons, remember the huge flocks that took days to pass?
Ma: Na, gone, eaten by humans.
Pa: Realy,,, oh.
Pa: Oh dear, what about chickens?
Ma: Oh ye there's billions of them, they might have trouble getting away for the party though.
Pa: I think we'll leave the birds for now, how about those glorious black rhinos?
Ma: Probably out of luck there, only a few left locked in zoos.
Pa: What? surely humans haven't eaten all of them?
Ma: Humans use their horns for penile enhancement.
Pa: Penile enhancement?
Is that really necessary? there's 7 billion of them!
Hey wait a minute, you're having me on aren't you, rhino horn wouldn't help with erections, would it?
Ma: No, and no.
Pa: Javan Tiger?
Ma: Gone, humans object to being eaten.
Pa: Sharks, I know there's still sharks, remember we watched that movie on the trip over here.
Ma: Well there are sharks but they get a bit nervous for their fins around humans.
Ma: Don't you want to continue with your list.
Pa: Ah no, I think I'll leave it till later.
Ma: Well don't leave it too long.