If you go to the Galápagos, and even if you go, as I did, in a herd of clumsy American tourists, you will at some point feel like a field biologist. Regulations dictate that you be accompanied by licensed guides, and ours reminded me of my favorite college professors: authoritative and rhetorical most of the time, with sudden bursts of passion when they get a whiff of their pet topic.

Within an hour of my arrival, one of the guides launched into the difference between the islands’ endemic, native and introduced species. Endemic species arrived naturally but struggled to survive in the strange environment. Over many generations, they gradually adapted and are now found, in their modified form, nowhere else