Averages are not essences. Darwin answered this false problem in a wonderfully simple way in his epochal book, On the Origin of Species , published in 1859. He admitted that if species never died, all life would form an unbroken continuum without natural boundaries to define categories and entities. But the vast majority of the species that have inhabited the earth have become extinct. Chimps and humans evolved as separate lineages, each with unbroken continuity from a common ancestor that lived some 6 million to 8 million years ago.
Nature provides no moral messages for our complex and confusing lives.
In this sense, we must regard the birthright of humanity as being truly inalienable in the most literal way. A person born into this biological entity cannot sell his or her membership for a mess of pottage or for all the world's gold and power. Every human being contributes equally to the full variation that defines our essence. In this sense, the most mentally limited person remains as fully and completely human as McGwire or Einstein. Stephen Jay Gould is a professor of geology, biology, and zoology at Harvard University.