As our climate changes, some animals seem to be able to adapt while others cannot. What makes adaptation possible? Can humans help it along?

As Professor Ruth DeFries aptly stated in her opening remarks at yesterday’s book launch for “The Big Ratchet,” if you look at satellite pictures of the earth, you see the imprint of the human species everywhere. Humans have come to dominate the planet. But how did this come to be? This question, among others, is what DeFries hopes to answer in her new book, “The Big Ratchet: How Humanity Thrives in the Face of Natural Crisis.” How did humans acquire the capability to spread out over the entire earth and control other species?