What (if any) is the shortest evolutionary process observed by humans? [duplicate]

Question

So when I think of evolutionary processes, I think of it taking millions of years to happen. Like how humans evolved from monkeys or birds evolved from dinosaurs (I know that is super-duper simplified). Or how humans have parts that we don't need or use (the appendix, for example), but we don't have any records of a time when it was. But I wonder if there have been any evolutionary processes that happened on a human timescale or if we have evidence of something evolving in, say, thousands of years instead of millions? I think this would be interesting to learn about.

Answer 1

Definition of evolution

The whole problem boils down to the definition of the term "evolution". Typically, evolution is defined as a change in allele frequency over time. See wikipedia > allele if needed.

Answer with definition "evolution = change in allele frequency over time"

Using this definition, any event of death or birth is an evolutionary event. As such, in the human species, there are about 6 evolutionary events per second! This number will vary a lot among species / lineage of course.

Do you want to consider another definition?

If you are willing to use another definition, I am happy to investigate how common are events matching this definition. Please make sure to clearly define the term so as to leave out possibility for subjective appreciation. If you need inspiration for definitions, you might want to have a look at this post.

Sidenote: Evolutionary experiments

You might be interest in evolutionary experiments. An evolutionary experiment consists at putting individuals in a lab, let them breed under some circumstances and let them evolve. Of course, doing such experiment with elephants would be pointless as the generation time is so long. Common species that we use for such experiments include E.coli, S. cervisae (yeast) and D. melanogaster (fruit fly). Some of these experiments can be as short as a few days while others have been running for decades.

Somewhat related posts

• How come most animals never seem to evolve over millenia?
• Evolutionary chronology - if any, which species have evolved in the last 100 years
• Why don't we keep evolving until we are super-human?

For a very introductive source of information in evolutionary biology, you can have a look at the website that @BryanKrause recommended: evo101

Answer 2

How are you defining "evolutionary event"? You can do a lab experiment to generate antibiotic-resistant bacteria from antibiotic-sensitive parents strains in a few days or weeks, I think.

Humans drive the dodo to extinction over the course of a few centuries.

In Lake Victoria: https://www.nytimes.com/1996/08/27/science/lake-victoria-s-lightning-fast-origin-of-species.html

Now an international team of researchers, using remote sensing to probe the sediments at the lake's bottom, have found evidence that what is now Lake Victoria was a dry, grassy plain just 12,000 years ago. For evolutionary biologists, the implications are enormous. The discovery means that the 300 unique fish species that have been documented in the lake must have evolved in the unthinkably short interval since the current lake began to form, a geological instant ago.

Another example:https://payseur.genetics.wisc.edu/IslandEvolution.htm

Gough Island, located in the South Atlantic about 3000 km southwest of South Africa, is home to the largest wild house mice in the world. These animals are about twice the mass of wild mice in the United Kingdom. Body size evolution has been rapid: mice were recently introduced to the island (in the 19th century) and a major size increase was observed over just a 40-year period. The drastic size change of Gough Island mice has been attributed to low temperature, extended longevity, reduced predation, and carnivorous eating habits. In a highly unusual behavior, these mice cooperatively feed on live and dead chicks of severely endangered albatrosses.