Answer to Question #194420 in Evolution for Natie Nel

Question

Discuss the mechanisms of evolution and discuss human evolution

Answer 1

Discuss the mechanisms of evolution

There are five main mechanisms of evolution: mutation, genetic drift, gene flow, non-random mating, and natural selection.

Mutation is the source of new alleles. We cannot predict when or in which individual a particular gene will mutate. We can predict an average mutation rate, the probability that a mutation will occur in a given interval, for a species.

Genetic drift is a random change in allele frequencies over time, brought about by chance. Genetic drift is pronounced when a few individuals rebuild a population or start a new one, such as occurs after a bottleneck – a drastic reduction in population size brought about by severe pressure.

Individuals of the same species do not always stay in the same geographic area, or in the same population. A population can lose alleles when individuals leave it permanently, an act called emigration. A population gains alleles when individuals permanently move in, an act called immigration. Gene flow, the movement of alleles among populations, occurs in both cases. Gene flow is a microevolutionary process that counters the diversifying effects of mutations, natural selection, and genetic drift in a population.

A common form of non-random mating is inbreeding. It refers to matings between relatives. Inbreeding leads to a decrease in the frequency of heterozygotes. The most intense form of inbreeding is self-fertilization, which may occur in hermaphroditic organisms.

Natural selection is differential survival and reproduction among individuals of a population that vary in the details of shared traits. Some traits prove more adaptive than others in prevailing environmental conditions. Natural selection influences all levels of biological organization.

Discuss human evolution

Human evolution (or anthropogenesis) is the process that led to the emergence of modern humans, beginning with the evolutionary history of primates and leading to the emergence of Homo sapiens as a distinct species of the hominid family, which includes the great apes.

All hominoids and hominids originated in Africa. The human lineage (Homo) arose by 2 million years ago, with H. habilis as an early toolmaking species. Bands of H. erectus dispersed into Europe and Asia. Extinct Neandertals and modern humans are close relatives, but have distinct gene pools.

Modern humans, H. sapiens, evolved by 195,000 years ago. By the multiregional model, H. erectus populations in far-flung regions evolved into H. sapiens. The African emergence model has modern humans evolving from H. erectus in Africa, then dispersing into regions already occupied by H. erectus and driving them to extinction. Most data now support the African emergence model. Its underlying premise is that regional variations among human groups evolved very recently.