Before Darwinism was generally accepted, the natural world was thought to be structured according to the chain of being. Evolutionary theories have revolutionized this imperialistic view, and the process we now know as natural selection explains a great many mysteries to us. One such enigma is the flamingo's smile, which is a perfect example of the way in which function (in this case feeding in saline lakes) and form (the inverted beak that enables the flamingo to feed more successfully) are inseparable. The 31 essays in this collection share the theme of quirkiness and meaning and explore the idea that natural oddities - the snail that changes sex, the jellyfish that feeds upside down - are extraordinary for a vital reason: they have found their evolutionary niche.