microevolution

noun

1. (countable, uncountable)Small-scale changes in the history of life, such as changes in allele frequencies in a population (over a few generations); also known as change at or below the species level.

   ““It basically hasn’t become this massive chewing and grinding machine that it becomes later,” Mr. Martin said. The change would have been the result of microevolution, or an evolutionary change occurring within a species.”