Humans are a timekeeping species, and much of our history can be traced to the ways we parse the moments of our lives. - Neil Shubin

Take the entire 4.5-billion-year history of the earth and scale it down to a single year, with January 1 being the origin of the earth and midnight on December 31 being the present. Until June, the only organisms were single-celled microbes, such as algae, bacteria, and amoebae. The first animal with a head did not appear until October. The first human appears on December 31. We, like all the animals and plants that have ever lived, are recent crashers at the party of life on earth.

What do billions of years of history mean for our lives today? Answers to fundamental questions we face—about the inner workings of our organs and our place in nature—will come from understanding how our bodies and minds have emerged from parts common to other living creatures. I can imagine few things more beautiful or intellectually profound than finding the basis for our humanity, and remedies for many of the ills we suffer, nestled inside some of the most humble creatures that have ever lived on our planet.

For thousands of years, mankind considered itself the pinnacle of life’s creation on a planet sitting in the center of the universe. Science changed that perception. Leavitt, Hubble, and others helped us see that we live near the margin of a vast galaxy, in a universe of galaxies, with our planet one of many worlds. Darwin and the biologists had their say too. Our entire species is but one little twig on an enormous tree of life filled with all life on earth. But each discovery that moves us from the center of creation to some obscure corner brings an entirely new relation between us, other species, and the entire universe.