How Long Does Evolution Take?

Part of the Darwin exhibition.

CELLS alive!Unlike most larger organisms, viruses and bacteria like E. coli reproduce very rapidly--they simply split in two every few minutes or hours, with both offspring continuing to divide and multiply.

Evolution has no single schedule. Sometimes, new species or varieties arise in a matter of years or even days. Other times, species remain stable for long periods, showing little or no evolutionary change. However, the characteristics of organisms that reproduce every few hours, such as bacteria, can potentially evolve much faster than in organisms with generations that are measured in months or years, such as horses.

CELLS alive!Such short spacing between generations can help speed up the evolutionary process.