The book is introduced by means of imagining the life of Homo sapiens about 10,000 years back. The female clan leader (since females lived longer) is about to move the clan to a new location as she notices the depletion of resources in that part of the coast (even the sea otters were moving). The low human population allowed us to use up resources and simply move to new locations thus allowing nature to rectify the damage. We no longer can do that.