Chapter 17: Charles Darwin and Evolutionary Thought

This chapter is basically an introduction to evolution. Despite popular belief, evolution did not begin with Charles Darwin. The theory was around long before Charles Darwin wrote his book, On the Origin of Species (1859). Darwin provided us with a reasonable explanation of how evolution could occur, natural selection. Why was the idea around for so long before a mechanism was suggested? Humans have long recognized certain aspects of evolution, such as:

1) Fossils leave evidence that the Earth has not always been as it currently appears. Species have gone extinct and apparently some species came after others (were not contemporaries of one another).

2) Biogeography – Organisms often display similarities to similar species that live in the same area, but are very different from those from other continents.

3) Comparative anatomy – Wings of bats, arms of humans and whale flippers have similar bones (homologous structures) while some snakes seem to have the remnants of pelvic bones.

4) Embryology – the embryos of many vertebrates go through similar stages.

 

Darwin observed much of this on his trip aboard the HMS Beagle. Upon his return, he worked for years on scientific writings until he was prodded by another writer (Alfred Wallace) to put his theory of natural selection into a book. Darwin’s theory of natural selection would become one of the most influential ideas ever proposed. While influential and impressive, it is rather simple in its logic. Stephen Jay Gould, during his life, was one of the most influential writers/thinkers on Darwin. Gould summarized Darwin into three main points:

1) All individuals display unique, genetic differences. Some of these differences help them survive in their world or attract mates.

2) All species, given enough time, will overpopulate. The result will be ultimate competition for resources and mates.

3) In part, those that survive and pass on their genes will do so because they are well adapted to their environment. ("Survival of the fittest," a term not used by Darwin, but often used to sum this point.)

 

Darwin was fighting the belief of a young Earth. Many people in his day thought the age of the Earth was measured in the thousands of years, not millions or billions. Later, when we cover geologic history, we will explain why we now view the Earth as being billions of years old. Don’t worry about reading this chapter, it is just a short intro to evolution.