How did Charles Darwin develop his theory?

In 1831, Charles Darwin, a young student of geology and botany, seized the opportunity he had of participating, as a naturalist, in an expedition around the world to continue his research.

He visited the Galapagos Islands.

In each of these islands, far apart from one another, he observed certain species that did not appear in the other islands of the archipelago.

Charles Darwin discovered that nearby islands had similar but nonidentical species of finches. Moreover, he noted that each finch species was well-suited for its environment and role. When he returned to England, he read carefully his remarks from the journey he had carefully recorded in the logbook every day.

Charles Robert Darwin (12 February 1809 – 19 April 1882)

After many years of study and reflection, Darwin concluded that all of nature was changing. According to him, the strongest and most intelligent individuals are best able to adjust to changed environmental conditions and transfer to their offspring maintenance-friendly properties.

He described his impressions in the book "The Voyage of the Beagle".

Other of Darwin's very significant works are: "On the Origin of Species", "The Descent of Man", "The Expression of the Emotions in Man and Animals", "The Power of Movement in Plants", "The Formation of Vegetable Mould through the Action of Worms"

Charles Darwin is best known for his contributions to the science of evolution. His proposition that all species of life have descended over time from common ancestors is now widely accepted and considered a foundational concept in science.