Why Study Fossils? thie hps catered times among ver ebrates. Birds and but pterosaurs, I grew up on the streets of New York City, such as the one in a family of modest means and little for- pictured,became mal education, but with a deep love of extinct with the di learning. Like many urban kids who be- nosaurs about 65 come naturalists, my inspiration came million years ago from a great museum-in particular, fre the magnificent dinosaurs on display at the American Museum of Natural History. As we all know from Jurassic Park and other urces,dinomania in young children (I was five when I saw my first dinosaur)is not rare-but nearly all children lose the Stephen Jay Gould passion, and the desire to become a pale Harvard University ontologist becomes a transient moment between policeman and fireman in a chro- nology of intended professions. But I per- geological time, occur by a natural process by studying modern organisms. But history sisted and became a professional paleontol- of evolutionary transformation-"descent is complex and unpredictable--and prine ogist, a student of life's history as revealed with modification, "in Darwins words. I ples of evolution(like natural selection) by the evidence of fossils(though I ended was thrilled to learn that humans had arisen cannot specify the pathway that life's histo- up working on snails rather than dino- from apelike ancestors, who had themselves ry has actually followed. Paleontology holds saurs. ). Why? evolved from the tiny mouselike mammals the archives of the pathway-the fossil I remained committed to paleontology that had lived in the time of dinosaurs and record of past life, with its fascinating histo- because I discovered, still as a child, the seemed then so inconspicuous, so unsuc- ry of mass extinctions, periods of rapi onder of one of the greatest transforming cessful, and so unpromising change, long episodes of stability, and con- ideas ever discovered by science: evolution. Now, at mid-career (I was born in 1941) stantly changing patterns of dominance and I learned that those dinosaurs, and all crea- I remain convinced that I made the right diversity. Humans represent just one tiny, tures that have ever lived, are bound to- choice, and committed to learn and convey, largely fortuitous, and late-arising twig on gether in a grand family tree of physical re- as much as I can as long as I can, about evo- the enormously arborescent bush of life changes of life, through billions of years in a great deal about the process of evolution all bushes y is the study of this grandest of Molecular Biology can even estimate the rates at which evolution is occurring Biochemical tools are now of major importance in efforts to in different groups of organisms reach a better understanding of how evolution occurs Within the last few years, for example, evolutionary biolo- Development gists have begun to"read"genes, much as you are reading Twentieth-century knowledge about growth and develop- this page. They have learned to recognize the order of the letters"of the long DNA molecules, which are present in ment further supports Darwin,s theory of evolution. Strik every living cell and which provide the genetic information ing similarities are seen in the developmental stages of nany organisms of different species. Human embryos, for for that organism. By comparing the sequences of"letters" example, go through a stage in which they possess the the dNA of different groups of animals or plants, we can same structures that give rise to the gills in fish, a tail, and specify the degree of relationship among the grou detailed ment of an organism (its ontogeny)often yields informa- more even a stage when the embryo has fur! Thus, the develop- family trees can then be constructed. The consistent pattern on about the evolutionary history of the species as a emerging from a growing mountain of data is one of pro- whole (its phylogeny) species showing more differences in their DNa than closely related ones, just as Darwin's theory predicts. By measuring Since darwin's time. new discoveries of the fossil the degree of difference in the genetic coding, and by inter- record, genetics, anatomy, and development all support preting the information available from the fossil record, we Darwin's theory 16 Part I The Origin of living thingsMolecular Biology Biochemical tools are now of major importance in efforts to reach a better understanding of how evolution occurs. Within the last few years, for example, evolutionary biolo￾gists have begun to “read” genes, much as you are reading this page. They have learned to recognize the order of the “letters” of the long DNA molecules, which are present in every living cell and which provide the genetic information for that organism. By comparing the sequences of “letters” in the DNA of different groups of animals or plants, we can specify the degree of relationship among the groups more precisely than by any other means. In many cases, detailed family trees can then be constructed. The consistent pattern emerging from a growing mountain of data is one of pro￾gressive change over time, with more distantly related species showing more differences in their DNA than closely related ones, just as Darwin’s theory predicts. By measuring the degree of difference in the genetic coding, and by inter￾preting the information available from the fossil record, we can even estimate the rates at which evolution is occurring in different groups of organisms. Development Twentieth-century knowledge about growth and develop￾ment further supports Darwin’s theory of evolution. Strik￾ing similarities are seen in the developmental stages of many organisms of different species. Human embryos, for example, go through a stage in which they possess the same structures that give rise to the gills in fish, a tail, and even a stage when the embryo has fur! Thus, the develop￾ment of an organism (its ontogeny) often yields informa￾tion about the evolutionary history of the species as a whole (its phylogeny). Since Darwin’s time, new discoveries of the fossil record, genetics, anatomy, and development all support Darwin’s theory. 16 Part I The Origin of Living Things by studying modern organisms. But history is complex and unpredictable—and princi￾ples of evolution (like natural selection) cannot specify the pathway that life’s histo￾ry has actually followed. Paleontology holds the archives of the pathway—the fossil record of past life, with its fascinating histo￾ry of mass extinctions, periods of rapid change, long episodes of stability, and con￾stantly changing patterns of dominance and diversity. Humans represent just one tiny, largely fortuitous, and late-arising twig on the enormously arborescent bush of life. Paleontology is the study of this grandest of all bushes. geological time, occur by a natural process of evolutionary transformation—“descent with modification,” in Darwin’s words. I was thrilled to learn that humans had arisen from apelike ancestors, who had themselves evolved from the tiny mouselike mammals that had lived in the time of dinosaurs and seemed then so inconspicuous, so unsuc￾cessful, and so unpromising. Now, at mid-career (I was born in 1941) I remain convinced that I made the right choice, and committed to learn and convey, as much as I can as long as I can, about evo￾lution and the history of life. We can learn a great deal about the process of evolution I grew up on the streets of New York City, in a family of modest means and little for￾mal education, but with a deep love of learning. Like many urban kids who be￾come naturalists, my inspiration came from a great museum—in particular, from the magnificent dinosaurs on display at the American Museum of Natural History. As we all know from Jurassic Park and other sources, dinomania in young children (I was five when I saw my first dinosaur) is not rare—but nearly all children lose the passion, and the desire to become a pale￾ontologist becomes a transient moment between policeman and fireman in a chro￾nology of intended professions. But I per￾sisted and became a professional paleontol￾ogist, a student of life’s history as revealed by the evidence of fossils (though I ended up working on snails rather than dino￾saurs!). Why? I remained committed to paleontology because I discovered, still as a child, the wonder of one of the greatest transforming ideas ever discovered by science: evolution. I learned that those dinosaurs, and all crea￾tures that have ever lived, are bound to￾gether in a grand family tree of physical re￾lationships, and that the rich and fascinating changes of life, through billions of years in Why Study Fossils? Flight has evolved three separate times among ver￾tebrates. Birds and bats are still with us, but pterosaurs, such as the one pictured, became extinct with the di￾nosaurs about 65 million years ago. Stephen Jay Gould Harvard University