VI Evolution Catching evolution in action A hundred years ago Charles Darwin's theory of evolution natural selection was taught as the foundation of biology in public schools throughout the United States. Then something happened. In the 1920s, conservative religious groups began to argue against the teaching of evolution in our nations schools. Darwinism, they said, contradicted the revealed word of god in the bible and thus was a direct attack on their religious beliefs. Many of you will have read about the 1925 Scopes"monkey trial"or seen the move about it, Inberit the Wind. In the backwash of this contro- The evolution of protective coloration in guppies. In versy, evolution for the first time in this century disap below waterfalls where predation is high, guppies are dn ools peared from the schools. Textbook publishers and local colored. In the absence of the highly predatory pike cichlid school boards, in a wish to avoid the dispute, simply chose guppies in pools above waterfalls are much more colorful and not to teach evolution. By 1959, 100 years after Darwins attractive to females. The evolution of these differences can be book, a famous American geneticist cried in anguish, "A hundred years without Darwin is enough! "What he meant was that the theory of evolution by natural selection has be- come the central operating concept of the science of biol ogy,organic evolution being one of the most solidly vali omy and history, relying on observation and deduction dated facts of science. How could we continue to hide this rather than experiment and induction to examine ideas truth from our children, crippling their understanding of about past events. science? Nonetheless, evolutionary biology is not entirely an ob- In the 1970s, Darwin reappeared in our nation's schools, servational science. Darwin was right about many things part of the wave of concern about science that followed but one area in which he was mistaken concerns the pace Sputnik. Not for long, however. Cries from creationists for at which evolution occurs. Darwin thought that evolution equal time in the classroom soon had evolution out of our occurred at a very slow, almost imperceptible, pace. How classrooms again. Only in recent years, amid considerable ever, in recent years many case studies of natural popula uproar, have states like California succeeded in reforming tions have demonstrated that in some circumstances evolu- their school curriculums, focusing on evolution as the cen- tionary change can occur rapidly. In these instances, it is tral principle of biology. In other states, teaching Darwin ossible to establish experimental studies to directly test remains controversial volutionary hypotheses. Although laboratory studies on While Darwin's proposal that evolution occurs as the fruit flies and other organisms have been common for esult of natural selection remains controversial in many more than 50 years, it has only been in recent years that local school boards, it is accepted by practically every biol- scientists have started conducting experimental studies of gist who has examined it seriously. In this section, we will evolution in nature review the evidence supporting Darwins theory. Evolu To conduct experimental tests of evolution, it is first ne tionary biology is unlike most other fields of biology in essary to identify a population in nature upon which strong which hypotheses are tested directly with experimental selection might be operating( see above). Then, by manipt methods. To study evolution, we need to investigate what lating the strength of the selection, an investigator can pre- hat the past, sometimes many millions of years dict what outcome selection might produce, then look and ago. In this way, evolutionary biology is similar to astron- see the actual effect on the population 419419 Catching evolution in action A hundred years ago Charles Darwin’s theory of evolution by natural selection was taught as the foundation of biology in public schools throughout the United States. Then something happened. In the 1920s, conservative religious groups began to argue against the teaching of evolution in our nation's schools. Darwinism, they said, contradicted the revealed word of God in the Bible and thus was a direct attack on their religious beliefs. Many of you will have read about the 1925 Scopes "monkey trial" or seen the move about it, Inherit the Wind. In the backwash of this contro￾versy, evolution for the first time in this century disap￾peared from the schools. Textbook publishers and local school boards, in a wish to avoid the dispute, simply chose not to teach evolution. By 1959, 100 years after Darwin's book, a famous American geneticist cried in anguish, "A hundred years without Darwin is enough!" What he meant was that the theory of evolution by natural selection has be￾come the central operating concept of the science of biol￾ogy, organic evolution being one of the most solidly vali￾dated facts of science. How could we continue to hide this truth from our children, crippling their understanding of science? In the 1970s, Darwin reappeared in our nation's schools, part of the wave of concern about science that followed Sputnik. Not for long, however. Cries from creationists for equal time in the classroom soon had evolution out of our classrooms again. Only in recent years, amid considerable uproar, have states like California succeeded in reforming their school curriculums, focusing on evolution as the cen￾tral principle of biology. In other states, teaching Darwin remains controversial. While Darwin’s proposal that evolution occurs as the result of natural selection remains controversial in many local school boards, it is accepted by practically every biol￾ogist who has examined it seriously. In this section, we will review the evidence supporting Darwin’s theory. Evolu￾tionary biology is unlike most other fields of biology in which hypotheses are tested directly with experimental methods. To study evolution, we need to investigate what happened in the past, sometimes many millions of years ago. In this way, evolutionary biology is similar to astron￾omy and history, relying on observation and deduction rather than experiment and induction to examine ideas about past events. Nonetheless, evolutionary biology is not entirely an ob￾servational science. Darwin was right about many things, but one area in which he was mistaken concerns the pace at which evolution occurs. Darwin thought that evolution occurred at a very slow, almost imperceptible, pace. How￾ever, in recent years many case studies of natural popula￾tions have demonstrated that in some circumstances evolu￾tionary change can occur rapidly. In these instances, it is possible to establish experimental studies to directly test evolutionary hypotheses. Although laboratory studies on fruit flies and other organisms have been common for more than 50 years, it has only been in recent years that scientists have started conducting experimental studies of evolution in nature. To conduct experimental tests of evolution, it is first nec￾essary to identify a population in nature upon which strong selection might be operating (see above). Then, by manipu￾lating the strength of the selection, an investigator can pre￾dict what outcome selection might produce, then look and see the actual effect on the population. Part VI Evolution The evolution of protective coloration in guppies. In pools below waterfalls where predation is high, guppies are drab colored. In the absence of the highly predatory pike cichlid, guppies in pools above waterfalls are much more colorful and attractive to females. The evolution of these differences can be experimentally tested