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Alfred Wallace: Theory of Evolution & Contribution

Instructor: Bridgett Payseur

Bridgett has a PhD in microbiology and immunology and teaches college biology.

This lesson explores Alfred Wallace's interest in evolution, his study subjects, and the development of his ideas. You'll learn how Wallace noticed the distribution of different species of animals and explained why new species could arise.

Theory of Evolution

Evolution is a word that conjures up grand ideas of single-celled organisms turning into dinosaurs turning into monkeys turning into humans. But what does the theory of evolution really tell us? And how did these ideas come together? What made past scientists want to begin looking for a common origin among different species?

Charles Darwin is famous for proving that all species have common ancestors. This is why we call him the father of evolution. But Darwin wasn't the only one to look for a common origin among different species.

Alfred Wallace studied how different species were distributed in different areas. This area of study is called biogeography. Wallace is known as the father of biogeography. He studied how and why different species were living in different places. Wallace studied many different species, especially those in Asia and the Amazon River basin in South America.

What Made Wallace Want to Study Evolution?

For many years, it was believed that the world and all living things on it had always been the same. For example, a frog had always been a frog. However, new ideas suggested that maybe this wasn't the case.

So what made Wallace study evolution? Well, he was inspired to study how species change over time for a variety of reasons. Firstly, he was interested in theories suggested by previous scholars who went against the establishment. One examples is Jean-Baptiste Lamarck, whose theo

In addition, Wallace, like Darwin, was inspired by an economics essay written by Thomas Malthus. The paper was titled 'Essay on the Principal of Population.' In his essay, Malthus explained that poverty-fighting policies would not work, because the population would continue to grow, and resources would not be able to keep up. While this may sound like an unlikely source of inspiration, both Wallace and Darwin noted that living organisms did not reproduce to their full potential, because there simply were not enough resources.

This brought up the question: Why do some individuals succeed at reproducing, but others don't? Wallace and Darwin both determined on their own that only those best suited to the environment could reproduce. It was similar to the idea that farmers would only breed the tastiest chickens, to ensure they only produced tasty chickens. Their ideas of species changing over time were so similar, that Darwin noted his letters from Wallace could serve as a nice introduction to his own book, On the Origin of Species.

There were, of course, some differences in Wallace's and Darwin's theories. While Darwin thought evolution was driven by competition between individuals, Wallace believed that the environment was the driving force. Basically, Wallace believed that species changed over time so they could fit into new environments. Another difference between Wallace's and Darwin's theories was that Wallace did not think that sexual selection played a major role in evolution. In both instances, we now know that Darwin was probably correct.

Speciation

Wallace, having studied biogeography, was particularly interested in how new species emerged. He guessed that if there was something preventing interbreeding between two groups of a population, this could lead to major changes between the groups. This idea was one of Wallace's greatest contributions and became known as the Wallace Effect.

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