Genetic drift - It is defined as the change in the frequency of a gene variant pr allele in a population due to natural random sampling of organisms during evolution. The alleles in the offspring are from the parents, and chance has a role in determining whether a given individual survives and reproduces. A populations allele frequency is the fraction of the copies of one gene that share a particular form. Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation.

Radiocarbon dating- It was a technique firsr proposed by Professor Willard Libby in 1940s. It is a method based on the fact that radiocarbon is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting radiocarbon then combines with atmospheric oxygen to form radioactive carbon dioxide. It comes into planta through photosynthesis. Then animals acquire 14C by eating these plants. When the animal or plant dies, it stops exchanging carbon with its environment, and then onwards the amount of 14C it contains begins to decrease as the 14C undergoes radioactive decay. Measuring the amount of 14C in a sample from a dead plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died. The older a sample is, the less 14C there is to be detected, and because the half-life of 14C (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by radiocarbon dating are around 50,000 years ago, although special preparation methods occasionally permit dating of older samples.