Sweetness isn't just triggered by sugar, but yeah.. still, our threshold for tasting sweetness (energy) is much higher than that for tasting bitterness (toxins), because energy is not really useful when it comes bundled with poison.

Alligator meat is fine (Was there really ever a time when alligators where tricky to kill though? I mean, at least compared to, say, lions or wolves, which consider humans a food source instead of being afraid of them like alligators are), but shark and whale meat don't seem like good ideas:

Sharks: http://en.wikipedia.org/wiki/Mercury_in_fish#Levels_of_conta...

Whales: http://www.hsi.org/issues/whaling/facts/human_health_concern...

> Pro-whaling nations insist that whale meat is healthier than beef. But the truth is that whales are particularly vulnerable to environmental contaminants, including organochlorines—such as polychlorinated biphenyl (PCBs), dichlorodiphenyltrichloroethane (DDT) and dioxin—and heavy metals, such as methylmercury. Each of these environmental contaminants tends to accumulate in the bodies of top predators, including sperm whales, orcas, pilot whales, and false killer whales