In textbooks and schools, evolution is often portrayed as a slow and tedious process that takes millennia to make substantial, noticeable changes in physiology. In actuality, this is not the case. Evolution can occur in rapid and sometimes violent displays of nature within the course of a few years, months, or even days.
Let’s first go back to the origin of the discovery of evolution, the Galapagos Islands, where Charles Darwin studied the changes in ground finches on different islands. Darwin used his observations to form the theory of evolution, which caused turbulent controversy at the time and entirely changed the way we think of the world's history. Some hundred years later, Peter and Rosemary Grant, a biologist couple, decided to verify Darwin’s findings with their own eyes. The couple traveled to one of the smallest and most untouched islands in the Galapagos, Daphne Major, and over a series of years, they recorded and studied every single finch on the island. The couple noted and observed all the previous findings of evolution on their routine trips to the Galapagos–until one fortunate day, a newcomer arrived.
A graduate student, who had joined the couple on one of their trips, noticed a finch that sang a strange song, one not familiar to the island of Daphne Major. The bird was much larger (giving it the nickname “big bird”) in beak and stature than all the others on the island, and the couple’s intricate knowledge that had been built up over several years allowed them to make the judgment that the finch wasn’t born on the island. Rather, the finch had traveled a remarkable 62 miles from the nearby Espanola island and was of the species Geospiza Conirostris.
The distance the finch had traveled from its home prevented it from traveling back to Espanola island to mate with a member of its same species, forcing it to mate with a species native to Daphne Major. The male Big Bird managed to find a mate despite his unusual song, with whom he produced a number of hybrid offspring. Once they reached maturity, however, the offspring didn’t have the same luck as their father. Their strange song repelled the other finches on the island, and they were unable to find mates of other lineages. The birds had no other option than to mate with the only other finches that looked like them: their siblings and parents. After the second round of mating had transpired, the offspring emerged as a brand new species. In just two generations, a new species had emerged because of traveling species, reproductive isolation, and inbreeding. Essentially, it's as if you were a slightly different species than your grandfather.
It’s highly probable that the “Big Bird lineage” isn’t the only new species of bird that emerged in the Galapagos islands, before or after Darwin's time. Researchers and scientists estimate that the majority of such species have appeared and gone extinct long before we had the chance to observe them. And although fleeting, instances of rapid evolutionary change in finches, or any other organism for that matter, provide the world with the competition and fitness necessary for the long, gradual, process of evolution that we’re familiar with to occur.