After Darwin and Natural Selection

AFTER DARWIN AND NATURAL SELECTION

Darwin largely ignored issues related to human evolution in his work because of the controversies associated with the idea that humans evolved from lower animals. It was first believed that humans existed on earth for just a few thousand years. Then, there were archaeological digs that stretched for many thousands of years, indicating that human ancestors existed for thousands of years before that. Java man was discovered in the 1890s, which served as a bridge between Neanderthals and modern man.

Thomas Henry Huxley wrote about the similarities between gorillas and humans, including similarities in brain structure. He wrote a book on the subject in 1863. Lyell and Wallace felt that there were similarities between apes and humans but felt that there was a common ancestor for each of the species of primates, including humans. Darwin later wrote that the differences between primate thinking and human thinking were a matter of degree rather than substance.

There were four major alternatives to the idea of natural selection that were espoused in the latter part of the 19th century. There was theistic evolution, orthogenesis, neo-Lamarckism, and saltationism. These are explained as follows:

• Theistic evolution—this basically tries to align science with modern religious beliefs and isn’t really a scientific theory at all.

• Neo-Lamarckism—this is the idea that use or disuse of a body structure allows it to be passed on or not passed on to the offspring.

• Orthogenesis—this involves the idea that there is a driving force that allows for evolution to go in a specific direction.

• Saltationism—this is the idea that a single mutation has the potential to change offspring into an entirely new species all in one step.

We will discuss Mendelian genetics in a few chapters. He discovered the laws of inheritance that became more popular around 1900. At the time, there were the Mendelians, who looked at variations in a species as they apply to the laws of inheritance. There were also the biometricians, who were more interested in the variation of specific characteristics within populations of organisms. These two camps opposed each other.

The two camps came together with the study of population genetics, which argued that larger changes in a population could come about by the natural selection and change in the frequencies