What on Earth Evolved? : 100 Species That Changed the World / Christopher Lloyd 415 p.

I picked this up for my husband and kids, and they never got a chance to look at it. Lloyd picks his top most important species based on his own (admittedly arbitrary) criteria: longevity, geographical spread, environmental impact, etc. Each species gets a short article, with nice illustrations and well-chosen anecdotes. It's fun to see what gets higher rank: smallpox or apples? vanilla or herpes? And can you guess his number -one pick? Spoiler: it doesn't have 2 legs!