A daptive changes in the genetic characteristics of a population over time--but this adaptation is not necessarily “improvement.” This entry says "Evolution" and not "Evolutionary Theory" because evolution is not a theory anymore. Evolutionary operations and outcomes have been observed directly, today, as well as indirectly through field studies, DNA research, evidence-dating techniques, the fossil record, etc. The animal equipped with a new and helpful feature is likelier to live long enough to pass it down than an animal without it.

Elephants in China are more frequently born tuskless, now, due to pressure from poaching. See Speciation for an example of a family of Asian butterflies branching into different species today. Genetic mutations, which are rare and usually harmful, play less of a role in evolution than Darwin believed, and cultural forces that reinforce selection for certain characteristics a larger role. (See Natural Selection and Sexual Selection.) According to biologist Richard Dawkins, the eye has evolved independently at least forty times, echo location four times, the venomous sting ten times, electrolocation several times, flapping flight four times, jet propulsion twice, and sound production for social purposes too many times to count. See Convergent Evolution, Taxonomy.