Being bitten by an Australian tiger snake is a wholly unpleasant experience. Within minutes, you start to feel pain in your neck and lower extremities -- symptoms that are soon followed by tingling sensations, numbness and profuse sweating. Breathing starts to become difficult, paralysis sets in, and if left untreated, you'll probably die. Remarkably, the venom responsible for these horrifying symptoms has remained the same for 10 million years -- the result of a fortuitous mutation that makes it practically impossible for evolution to find a counter-solution.