And so in 1975, the grizzly bear was put on, as I said - on the endangered species list as threatened. And new measures were taken, for instance, bear-proofing garbage, creating new regulations to - essentially to try and keep people and people's food away from the bears, let the bears adjust to eating the abundant wild food that's available in Yellowstone and allow them to be more wild, to be independent of humans as sources of foods for the good of both sides. And that has been quite successful.

By the cold Darwinian logic of natural selection, evolution codifies happenstance into strategy.

Wallace's sales agent, back in London, heard mutterings from some naturalists that young Mr. Wallace ought to quit theorizing and stick to gathering facts. Besides expressing their condescension toward him in particular, that criticism also reflected a common attitude that fact-gathering, not theory, was the proper business of all naturalists.

But private lands development around the periphery of the parks - Grand Teton and Yellowstone - is a crucial issue because if those private lands are transformed from open pastures, meadow, forest land to suburbs, to little ranchettes, to shopping malls, to roads, to Starbucks - if those places are all settled for the benefit of humans, then the elk are not going to be able to migrate in and out of Yellowstone Park anymore. And if the elk can't migrate into the park, then that creates problems for the wolves, for the grizzlies, for a lot of other creatures.

Whether you like the label 'Anthropocene' or not, whether you find the prospect of what it signifies inevitable or appalling (or both), the time has come to address its implications, as these thoughtful, battle-tested authors attempt to do. The time has long since come.

Islands are where species go to die.

If you're Maasai Mara National Park in Kenya, if you're in Serengeti National Park in Tanzania, you don't get out of your vehicle and go walking around amid the lions and the leopards. You stay in your Land Rover. You stay in your safari van, and you look out the windows or you look out the pop top at these animals. I know by experience how badly that can work out if you violate those guidelines.