What observation initialized the concept of natural selection?

The concept of natural selection was significantly influenced by the observation of finch beak variety, particularly on the Galapagos Islands. Charles Darwin studied these finches and noted how variations in their beak shapes and sizes corresponded to the types of food available on different islands. For example, finches with larger, stronger beaks were better adapted to cracking open hard seeds, while those with smaller beaks were more suited for feeding on softer fruits. This variation in beak morphology illustrated how certain traits could provide an advantage in specific environments, leading to differential survival and reproduction.

These observations laid the foundation for Darwin's theory of natural selection, which posits that organisms with favorable traits are more likely to survive and reproduce, passing those advantageous traits to the next generation. The finches became a classic example of adaptive evolution, showcasing how small, inheritable variations can drive the process of evolution based on environmental pressures.