Fifty-five million years ago, a furry, hoofed mammal about the size of a dog ventured into the shallow brackish remnant of the Tethys Sea and set its descendants on a path that would lead to their complete abandonment of the land. These early ancestors of cetaceans (dolphins, porpoises, and whales) thereafter set on an evolutionary course that is arguably the most unusual of any mammal that ever lived. Primates and cetaceans, because of their adaptation to exclusively different physical environments, have had essentially nothing to do with each other throughout their evolution as distinct orders. In fact, the closest phylogenetic relatives of cetaceans are even-toed ungulates.
Given this independence, what possible relevance could the study of cetaceans have for understanding primate behavioral evolution?
And what could we possibly learn about primates by comparing them to cetaceans that we could not learn from studying primates themselves? The answer to these questions is straightforward By comparing cetaceans and primates we can differentiate between the characteristics that are unique to primates and those that result from general factors that have shaped behavioral evolution in mammals. These two groups' disparate evolutionary histories and consequent organizational differences stand in stark contrast to their shared level of