READ: Macro Evolution

Rates of Evolution

How fast is evolution? How long did it take for the giraffe to develop a long neck? How long did it take for the Galápagos finches to evolve? How long did it take for whales to evolve from land mammals? These and other questions about the rate of evolution are difficult to answer, but evidence does exist in the fossil record.

The rate of evolution is a measurement of the speed of evolution. Genetically speaking, evolution is how much an organism’s genotype (the genes that make up an individual) changes over a set period of time. Evolution is usually so gradual that we do not see the change for many, many generations. Humans took millions of years to evolve from a mammal that is now extinct.

Not all organisms evolve at the same rate. It would be difficult to measure evolution in your family because you are only looking at a small population over a few generations. However there are organisms that are evolving so fast that you may be able to observe evolution! Many scientists use bacteria or other species that reproduce frequently to study evolution. Species with short life cycles and that reproduce frequently evolve much faster than others. Bacteria evolve hundreds (or thousands or more) times faster than humans do. Bacteria go through many generations in a few days, so that we can actually witness evolution. A human takes about 22 years to go through one generation. But some bacteria go through over a thousand generations in less than two months.

CK-12 Foundation, Biology. http://creativecommons.org/licenses/by-nc-sa/3.0/