"Poisons can be bad for some things and good for others, including humans," said Michael Novacek, senior vice president of the American Museum of Natural History, at an opening of a new poison-themed exhibition Tuesday (Nov. 12).

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The strongest of poisons occur in evolutionary arms races, Siddall explained. For example, opossums can feed upon some venomous snakes thanks to a resistance to the snakes' venom. In response, the snakes over generations have amped up the toxicity of their venom to keep these marsupial predators at bay. Meanwhile, the opossums continue to evolve resistance to the ever-stronger venom, he said.