Final answer:
Darwin used fossil evidence, his observations of Galápagos tortoises, evidence from geology suggesting an older Earth, and biogeographical distribution to support his theory of evolution.
Step-by-step explanation:
Charles Darwin used several lines of evidence to support his theory of evolution, with his book On the Origin of Species presenting significant evidence. Four pivotal lines of evidence include:
- Fossil Evidence: Darwin found fossils such as the ground sloth, which suggested that organisms in the past looked different from present-day organisms.
- Observations of Galápagos tortoises: Their unique adaptations to specific environments on the islands supported the idea that species adapt over time to their habitats.
- Understanding the age of the Earth and geological changes: Influenced by Charles Lyell, Darwin reasoned that geological formations and fossil discoveries in unexpected places (such as sea life fossils high in the mountains) indicated a much older Earth that was constantly changing.
- Biogeography: The distribution of species and ecosystems in geographic space and through geological time showed patterns that were consistent with organisms evolving in particular habitats.
These observations collectively supported the concept that lifeforms evolve, a key component in Darwin’s theory of natural selection. Darwin’s detailed research provided not just singular evidence but an intertwined set of facts and observations that solidified his groundbreaking ideas on biological evolution.