Inception of Darwin's theory

When Charles Darwin returned from his journey on the survey voyage of the Beagle, he was already known for his work with fossil collections and geologist studies. His father gave him money to work as a gentleman naturalist instead of becoming a clergyman. Darwin’s first tasks were to find experts to describe his collections, write about his experiences, 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, and birds from the Galápagos Islands were different but related to their places. This made Darwin think that species could change over time. He wrote down his early ideas about evolution in his Red Notebook and started notebooks about how species might change to fit their world. 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, just like nature might do. He also thought about how animals’ habits and minds might change over many generations. While working on these ideas, he got very busy and sometimes felt unwell. He also thought about marrying his cousin Emma Wedgwood.

Reading about a writer named Malthus, Darwin began to think about how animals might struggle to survive without help. This helped him form his theory. He compared how farmers choose traits in animals to what nature might do by chance. He got married to 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 suggest 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 traveled to his family home in Shrewsbury and then went to Cambridge for advice on organizing his collections from the voyage. He met with scientists who helped him describe and catalog his findings.

Darwin met with anatomist Richard Owen, who studied the fossils Darwin had collected. Owen discovered that some extinct animals were related to living species in the same areas. Ornithologist John Gould examined bird specimens from the Galápagos Islands and found they were different species depending on their locations, not just slight variations. These discoveries began to shape Darwin’s thoughts about how species might change over time.

Transmutation

Darwin wanted to make sure his ideas followed the scientific methods used by other scientists. He talked about his work with two important scientists, John Herschel and William Whewell. At that time, many scientists were thinking about how species change over time.

Darwin kept a special notebook where he wrote down his thoughts and observations from his travels. In March 1837, after talking to scientist John Gould, Darwin began to think that species might change suddenly instead of slowly. He noticed that some birds and animals in different places seemed to be related but were different species. This helped him start forming his ideas about how species might change over time.

Transmutation notebooks

In mid-July 1837, Charles Darwin started filling up his Red Notebook. He then began two new notebooks: his "A" notebook on geology, and his "B" notebook, which was the first in a series about the "transmutation of Species". In this notebook, Darwin wrote down his early ideas about evolution.

The "B" notebook began with questions about why some animals produce copies of themselves while others produce offspring that are different. Darwin thought that while adult animals might not change much, the differences in their young could help species adapt to new environments. He also wondered how animals could reach new places, like islands, and how this might lead to new species forming.

Darwin also started a new notebook called the C notebook in February 1838. In this one, he looked at how domestic animals, like those in zoos, were bred. He noticed similarities between humans and animals and began to think about how 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 enjoyed 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 that helped him understand nature better. This book showed that populations grow faster than resources, leading to competition. Darwin saw that this idea could also apply to animals, not just people.

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

Proposal

Charles Darwin continued to think and work, but he often felt unwell. 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 very 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 days looking for a new home. At night, he thought about how many small changes in animals could, over 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 served 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, so there is 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 excitedly wrote to his future wife, Emma, about their new place, calling it "Macaw Cottage" because of its brightly colored walls and furniture.

On January 29, 1839, Charles married Emma in Maer, Staffordshire in a special ceremony that worked for both Anglican and Unitarian traditions. Right after the wedding, they hurried to the train station and celebrated their new life together with sandwiches and a bottle of water during the journey 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 the ensuing developments, in the context of his life, work and outside influences at the time.