Inception of Darwin's theory

Charles Darwin returned from his journey on the survey voyage of the Beagle. He was known for his work with fossil collections and geologist studies. His father gave him money to work as a gentleman naturalist.

Darwin’s first tasks were to find experts to describe his collections and share his discoveries with the Geological Society of London. Reports by scientists like Richard Owen and John Gould showed that extinct species were linked to living ones. Birds from the Galápagos Islands were different but related. This made Darwin think that species could change over time.

He wrote down his early ideas in his Red Notebook and started notebooks about how species might change. He even drew a branching tree to show how one species could lead to many others. Darwin also watched an orangutan at the zoo and saw how much its expressions looked like a human’s. This helped him believe there was not a big difference between humans and animals.

He studied how farmers choose which animals to breed and saw that this changed the animals a lot over time. He thought about how animals’ habits might change over many generations. While working on these ideas, he felt unwell and thought about marrying his cousin Emma Wedgwood.

Reading about a writer named Malthus, Darwin began to think about how animals might struggle to survive. This helped him form his theory. He compared how farmers choose traits in animals to what nature might do by chance. He married Emma and was elected to the Royal Society in 1839. From there, he continued to develop his big ideas about how species change over time, known as the development of Darwin's theory.

Background

Charles Darwin was not the first to think that species could change over time. In later versions of his famous book On the Origin of Species, Darwin talked about earlier thinkers who had similar ideas. He mentioned that Lamarck was one of the first to get a lot of attention for this idea. Darwin also noted that his own grandfather, Dr. Erasmus Darwin, along with Goethe and Geoffroy Saint Hilaire, had similar thoughts around the same time.

Darwin grew up in a Unitarian family and became very interested in natural history. While studying at Edinburgh University, he worked with Robert Edmund Grant and learned about ideas of change in species. Later, at Christ's College, Cambridge, he loved collecting beetles and studied plants with John Stevens Henslow. During his trip on the Beagle, Darwin was influenced by Charles Lyell's ideas about slow changes in the earth over time. He wondered how different kinds of life fit into what he saw, but he did not come up with his big idea about evolution during that trip. He felt that until he could explain how animals and plants fit so perfectly into their homes, it was too early to prove that species change.

Return to England

When the ship Beagle returned, Charles Darwin arrived back in England on October 2, 1836. He went to his family home in Shrewsbury and then to Cambridge for help with his collections from the trip. He met scientists who helped him describe and sort his findings.

Darwin met anatomist Richard Owen, who studied the fossils Darwin brought back. Owen found that some animals that no longer lived were related to animals still living in the same places. Bird expert John Gould looked at bird samples from the Galápagos Islands and saw they were different species depending on where they lived, not just small changes. These discoveries started to shape Darwin’s ideas about how species might change over time.

Transmutation

Darwin wanted his ideas to follow the rules of science. He talked about his work with two scientists, John Herschel and William Whewell. At that time, many scientists were thinking about how animals and plants change over many years.

Darwin kept a notebook where he wrote down his ideas and things he saw on his travels. In March 1837, after speaking with scientist John Gould, Darwin started to think that animals and plants might change in big steps, not just little steps. He noticed that some birds and animals in faraway places looked similar but were different kinds. This helped him begin to form his ideas about how species change over time.

Transmutation notebooks

In July 1837, Charles Darwin started using his Red Notebook. He also began two new notebooks: his "A" notebook on geology, and his "B" notebook about how species change over time. In the "B" notebook, Darwin wrote his early ideas about evolution.

The "B" notebook started with questions about why some animals look very similar to their parents, while others have differences. Darwin thought that even small changes in young animals could help species adapt to new places. He also wondered how animals could get to new areas, like islands, and how this might create new species.

In February 1838, Darwin started another notebook called the C notebook. In it, he studied how animals like those in zoos were bred. He saw similarities between humans and animals and began to think that all living things might be connected.

Thoughts of marriage

Charles Darwin was staying near his friend Hensleigh Wedgwood. In June 1838, his cousin Emma Wedgwood visited, and they had happy times together.

Darwin felt unwell and decided to travel to Scotland for a break. He visited places like Edinburgh and Glen Roy, where he studied old paths near the valley. After feeling better, he returned home and thought deeply about marriage. He made a list of reasons to marry and reasons not to. He decided that marriage was better, imagining a cozy life with a loving wife instead of working alone in a smoky city. He later visited Emma again and shared some of his big scientific ideas with her, though he was still unsure about some parts of his theory.

Malthus and natural law

After returning to London in August 1838, Charles Darwin read a book. The book showed that populations grow faster than resources, leading to competition. Darwin saw that this idea could also apply to animals.

He realized that when there are more animals than food or space, only the animals best suited to survive would live on. This helped him develop his theory about how new species form over time.

Proposal

Charles Darwin kept thinking and working, but he often didn't feel well. On November 11, he went back to Maer Hall and asked Emma to marry him.

They talked about their different ideas. Emma wrote to him, saying she was worried they might not agree on important matters. She told him she believed being honest about doubts was okay, but she hoped they would not cause problems between them. She asked him to read a special part of the Bible, where Jesus tells his friends to love each other. This was important to her because she believed strongly in faith, especially after her sister Fanny passed away. She hoped Darwin would also find belief.

Darwin wrote back kindly, and Emma felt better. She was happy he was serious about these matters and thought they agreed. Even so, they would still have some differences to think about.

Emma’s father promised money to help them start their life together, and they planned to live in London for a while before deciding where to settle down.

Theory

Charles Darwin spent his time looking for a new home. At night, he thought about how small changes in animals could, over a long time, lead to big differences. He believed that nature chose the best changes, helping species to change step by step. He also thought that parts of the body that no longer had a purpose, like the small tail bones in humans, were reminders of our past.

Darwin also read about ideas from other thinkers. One idea, from a writer named Malthus, said that people often have more children than the land can support. This creates competition for food and space. Darwin used this idea to help explain how species might change over time. He thought that nature, like people who breed animals, could choose which traits were best for survival.

Marriage

On December 29, 1838, Charles Darwin moved into a rented house at 12 Upper Gower Street. He wrote to his future wife, Emma, about their new home.

On January 29, 1839, Charles married Emma in Maer, Staffordshire. Their special ceremony worked for both Anglican and Unitarian traditions. After the wedding, they travelled back to London. That same day, Charles wrote in his journal about getting married and returning to London at the age of 30.

See the development of Darwin's theory for what happened next.