Evolution

Paleolithic period or Old Stone Age, the earliest period of human development and the longest phase of mankind's history. It is approximately coextensive with the Pleistocene geologic epoch, beginning about 2 million years ago and ending in various places between 40,000 and 10,000 years ago, when it was succeeded by the Mesolithic period. By far the most outstanding feature of the Paleolithic period was the evolution of the human species from an apelike creature, or near human, to true Homo sapiens (see human evolution). This development was exceedingly slow and continued through the three successive divisions of the period, the Lower, Middle, and Upper Paleolithic. The most abundant remains of Paleolithic cultures are a variety of stone tools whose distinct characteristics provide the basis for a system of classification containing several toolmaking traditions or industries.

Natural selection is the gradual natural process by which biological traits become either more or less common in a population as a function of the effect of inherited traits on the differential reproductive success of organisms interacting with their environment. It is a key mechanism of evolution. The term "natural selection" was popularized by Charles Darwin who intended it to be compared with artificial selection, which is now called selective breeding.

About six million years ago in Africa, the chimpanzee lineage and our own split. What happened to us after that split? The hominid lineage did not march in a straight line to Homo sapiens. Instead, the early hominid lineage gave rise to many other (now extinct) hominids. Examining the fossils, the artifacts, and even the DNA of these relatives has helped us understand how this complex hominid tree evolved, and how modern humans came to exist.

This video discusses how variations in organisms become adaptations that drive the evolution of a species.

This lesson will give an in depth explanation of Reproductive Barriers. This lesson will look at Macroevolution and the Reproductive Barriers associated.