The risk of pain is not something that everyone is averse to. Risk can be exciting, which explains why many people take up risk sports such as boxing, free-fall parachuting and snow-boarding. For centuries, explorers risked starvation, disease, along with death by growing, by attack from wild animals and by attack from those whose territory they invade. There are many for whom being able to survive in the most hostile environment provides the greatest thrill, and those for whom the threat of danger is the spice of life.