Evolutionary Biology

A branch of biology that deals with the descent by modification of plants and animals from earlier generations.

Evolutionary biology rests on two principles: variation and selection. Natural selection was proposed by Charles Darwin in his 1859 publication, The Origin of Species. It is a process that promotes or maintains adaptation by filtering out among the variations in progeny those most fit to survive, and thus gives creatures the appearance of purpose or design. What was missing for Darwin was a theory of inheritance that would explain the basis and preservation of variations on which natural selection could act. Simultaneous with Darwin ’s work, but unknown to him, the Augustinian monk Gregor Mendel developed just what was needed in his study of peas. In 1900, Mendel’s genetic theory of heredity was rediscovered by evolutionary biologists. After several decades of research by geneticists such as R. A. Fisher, J. B. S. Haldane, and Sewall Wright, and culminating in the work of Theodosius Dobzhansky in 1937, Mendelian genetics was fully integrated into Darwin ’s theory of natural selection in what is now called the modern or synthetic theory of evolution. In 1953, James Watson and Francis Crick discovered the molecular structure of DNA, the hereditary material contained in the chromosomes of the nucleus of each cell. DNA in turn consists of two long chains of nucleotides coiled into a double helix. A gene is a sequence of nucleotides required for the production of a specific protein; the information needed is encoded in the specific sequence of these nucleotides. The DNA molecule is copied during routine cell division (mitosis) as well as during sexual reproduction (meiosis), thus preserving and transmitting hereditary information. Miscopying and other forms of genetic mutation constitute a major source of biological variation.

In recent decades, the modern synthesis has been extended to include paleontology, comparative anatomy, biogeography, embryology and molecular genetics. Research areas include the processes of speciation, gradual versus punctuated evolution, protein evolution, the neutrality theory of molecular evolution, the molecular evolutionary clock, multiple forms of selection at the level of gene, organism, kin, group, and species, and the possibility of additional sources of biological novelty besides mutation and selection. There are also a variety of scientific theories pushing the frontiers of evolutionary and molecular biology from the perspective of physics, including chaos, complexity, and self-organization, particularly through the work of Stuart Kauffman. Moreover, research on human evolution is focusing on what distinguishes our species from other early hominids, including such possibilities as bipedalism, brain size, language and tools, as well as on the biological basis of morality.

Related Topics:

	Genetics
	Evolution

Contributed by: Dr. Robert Russell