Charles Darwin

Young Charles Darwin & His Journey(1831-1836)

So Darwin signed on for a 5-year voyage around the world to chart the coastline of South America and some of the islands of the Pacific Ocean. He served as the naturalist on the British ship the HMS Beagle. During his journey Darwin collected thousands of plant and animal samples. He kept careful note of his observations while traveling to some very interesting places.

In 1831, 21 year-old Charles Darwin graduated from college. Like many young people just out of college, Darwin didn’t know what he wanted to do with his life. His father wanted him to become a doctor, but seeing blood made him sick. Although he eventually earned a degree in theology, Darwin was most interested in the study of plants and animals.

Galapagos Islands

This observation puzzled Darwin. Once back in England, Darwin hypothesized that many of the species on the Galapagos Islands were descended from South American species. They may have been brought to the Galapagos by storms or other circumstances. Over many generations, the species on the Galapagos adapted to different ways of life on the different islands, such as, the types of food each species relied on for survival. Eventually they became a separate species from their ancestors from South America.

One unique place Darwin visited on his trip was the Galapagos Islands. The islands are found 600 miles west of Ecuador in South America. Darwin noticed that life on the Galapagos were similar to species in South America, but not exactly the same.

Darwin’s Tree of Life

All life is connected through evolution (change over time)

Darwin’s Book: The Origin of Species (1859)

Provided an abundance of evidence and the theory of Natural Selection which explains how evolution happens.

Influences on Darwin

• Geology & Charles Lyell

• Selective Breeding (Artificial Selection)

• Population Control & Thomas Malthus

• Alfred Wallace & his Essay

Charles Lyell & Geology

During Darwin’s journey on the H.M.S. Beagle he had an opportunity to read the first volume of his good friend, Charles Lyell’s newly published book The Principles of Geology. Lyell proposed in his book that the earth was very old, that it had been slowly changing for millions of years, and that it was still changing. These changes were taking place from weathering, erosion and deposition. Most of the geologists of the time did not think the Earth was old enough to allow for slow changes.

After Darwin returned home from his voyage, he spent a great deal of time studying his notes, reading, and conversing with colleagues. He incorporated the ideas from Lyell’s book about the earth into his own thoughts on how life changes on earth. Using Lyell’s hypothesis, Darwin concluded that gradual geologic changes over long periods of time could cause life to change over that same long period of time.

Charles Lyell (1797-1875)

If the earth is extremely old and can change slowly overtime, life must change with it.

Selective Breeding (Artificial Selection)

Darwin also studied the selective breeding of domestic animals and crops. By selecting parents with the most desirable traits, farmers and animal breeders can raise more desirable offspring. Breeders, for instance, select cattle for increased milk production (Holstein), for high-butterfat milk (Jersey), or for meat (Hereford). Animal breeders and farmers determine which members of the population shall reproduce and which shall not. Any domesticated plant or animal bred to produce desirable characteristics is the result of artificial selection. The striking changes produced over relatively few generations are powerful proof that species can evolve. Darwin suspected that a selection process also occurred in nature. If we can select for useful traits in organisms through selective breeding; why can’t nature select traits in organisms that make them more successful to survive.

JerseyHolstein Hereford

Selective Breeding (animals)

Selective Breeding (plants)

If humans can select traits in species why can’t nature

Thomas Malthus & Population Control

Shortly after Darwin returned to England, he read An Essay on the Principles of Population by the economist Thomas Malthus. Malthus stated in his essay that the human population was growing so fast that the supply of resources could not keep up with demand. Malthus reasoned that the human population increases exponentially. For example, if each pair of parents produced four children, the new generation would have 4 individuals to replace the 2 that had produced them. The next generation would have 8, the next 16, and so on. This type of population growth will eventually exceed its available resources. According to Malthus, when a population exceeds its resources, disasters such as war, starvation, or widespread disease limit the population’s growth.

Darwin recognized that Malthus’s principles applied not only to humans, but to all species. Any species can produce many offspring. He also knew that the populations of all species are limited by starvation, disease, competition, and predation. Only a limited number of individuals survive to reproduce. Darwin reasoned that the offspring of the survivors inherit traits that help the offspring survive in their environment.

Thomas Malthus (1766-1834)

If humans over reproduce so do animals in nature, but competition keeps populations in check

Alfred Wallace & His Essay

In 1858, Alfred Wallace, a young British naturalist and explorer, wrote Darwin from Malaysia while he was on expedition. Wallace was seeking Darwin’s advice about a theory he had. At the time Darwin was one of the leading naturalists of England. However, Wallace had no idea of Darwin’s life work on his theory of natural selection because Darwin had only shared his ideas with a few close colleagues. Wallace sent Darwin an essay on his theory and it turned out that Wallace had struck upon the theory of natural selection that Darwin had been researching for 20 years. Wallace’s short sketch was far from the massive body of evidence Darwin had collected, but its core ideas were similar.

Darwin and Wallace agreed that Wallace’s essay should be published along with a summary of Darwin’s theory. A year later, in 1859, Darwin published his book under the title The Origin of Species. Darwin’s book was fully supported by examples and 20 years of research and influence. His theory on how evolution works was eventually accepted around 1865 by most of the leading scientists of his time. Without Wallace’s prompting, Darwin might never have published his theory during his lifetime.

Alfred Wallace (1823-1913)

Also came up with Natural Selection, but didn’t have as much evidence.