to understand process rather than to describe content. In other words, what an organism does is more empirically verifiable (and thus, reliable) than the internal processes leading to the observable.
Over the course of thirty years, Charles Darwin studied animals and plants. On the Galapagos Islands he found animals that were like those of the South American continent, but not exactly alike. He realized that they must have come to the islands from the mainland, and then changed into new species. He also observed the animals and plants of South America, oceanic islands, and the Far East, observing other animals in similar environments that did not always look exactly alike. For example, the emus of Australia and the rheas of South America looked alike, but not exactly alike, and yet they occupied the same kind of habitat. If animals were formed for a specific habitat, why would different species be found in similar habitats? By the time his Origin of Species was published in 1859, Darwin was convinced that all living things arose by evolution, the change in living things over very long periods of time.
Based on his observations and studies, Darwin developed his theory of evolution. Although modified by knowledge since the publication of his ground-breaking work, Darwin's ideas still form the cornerstone of modern evolutionary thought. His observations, or evolutionary l
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