The Story of Darwin

of a large number of genes in a population. This was believed to be how new species could be developed. We will talk about the evolution of moths in populations where being a certain color offered better protection against predators. This indicated that natural selection could actually happen quite quickly.

Modern synthesis of evolutionary thought came about in the twentieth century. This combined natural selection, genetic variation, and Mendelian inheritance into modern evolutionary thinking. There was a shift away from pure natural selection to ideas related to genetic drift within a population. A species came to be defined as a population of organisms that could breed together and that were reproductively different and isolated from others in the population.

In the middle of the twentieth century, there was a rise in molecular biology and the discovery of DNA and genetic codes. Biochemists Emile Zuckerkandl and Linus Pauling developed the molecular clock theory, which was that sequence differences between related proteins in different species could help define how far apart they were in terms of species divergence.

By the late twentieth century, there came to be a more gene-centered view of evolution. It was believed that sexual reproduction helped to create better resistance among the offspring to parasites and other pathogenic organisms. Sexual reproduction creates genetic diversity, which is felt to be better for the species overall. Whether or not sexual reproduction is truly better for a species or not is still the subject of debate.

Most of evolutionary thought was developed without the background of microbiology. Because of advances in the study of the genes in microbes, called microbial genomics, small microorganisms can be studied as to the differences in the species. Horizontal gene transfer was identified in 1959, which is the way that pieces of genetic material can be transferred between different bacterial species, which in many cases, leads to antibiotic resistance. This phenomenon is believed to play a role in creating new species of microorganisms.

THE STORY OF DARWIN

As you have seen, Charles Darwin did not develop his theories on evolution and the origin of species in a vacuum. His weren t the first words on evolution in the world and they haven t been the last words on the subject. Even so, he did a remarkable job of studying certain populations and wrote a landmark book On the Origin of Species.

Darwin gained a reputation as an important fossil collector and geologist. He studied naturalism rather than become a clergyman. He became convinced in the idea of the

transmutation of species after learning about bird specimens gathered from the Galapagos Islands. He also studied orangutans in the zoo as to their facial expressions; he studied animal breeding and how that changed the fitness of subsequent litters of domesticated animals.

He initially studied under Robert Edmund Grant and learned of Lamarck s ideas and the work of his grandfather Erasmus Darwin, showing a common ancestor to modern animals and plants. He collected beetles and took his voyage to other parts of the world on a ship called the Beagle. He did not develop his evolutionary ideas because of his work on the Beagle, however.

While on the Beagle, he collected numerous fossils and zoological specimens. Afterward, he looked around for zoologists to help him catalog his specimens. It was actually ornithologist John Gould who took on the bird specimens Darwin had collected; it was Gould who recognized that the birds collected were actually about 12 different species of finches.

Darwin was extremely concerned that his work met the accepted scientific methodology of the day. He did not want to simply present theories; he wanted facts to back them. There were many who believed in theistic evolution at the time and, while he was a religious man, he wanted to be very scientific about his findings.

He came to understand that, while individual organisms did not change over time, their offspring could change because of the reproductive process. Those offspring that adapted better could bring forth offspring that also fared better when it came to adaptation. He felt that geographic isolation led to reproductive isolation of species that lived there. This would lead to divergence of species and to what he called geographic speciation. It was exactly these circumstances that existed on the Galapagos Islands.

Darwin actually wrote about a number of things besides the origin of species. He wrote about barnacles, geological topics including earthquakes, and orangutans in the zoo. He was ill throughout most of his adult life but still kept a busy working life, ultimately writing his seminal work on the origin of species more than 20 years after his voyage on the Beagle.