Evolutionary biology

For the textbook, see Evolutionary Biology (textbook).

Evolutionary biology is the subfield of biology that studies the evolutionary processes that produced the diversity of life on Earth starting from a single origin of life. These processes include the descent of species, and the origin of new species.

The discipline emerged through what Julian Huxley called the synthesis of understanding from several previously unrelated fields of biological research, including genetics, ecology, systematics and paleontology.

Current research has widened to cover the genetic architecture of adaptation, molecular evolution, and the different forces that contribute to evolution including not only natural selection but sexual selection, genetic drift and biogeography. The newer field of evolutionary developmental biology ("evo-devo") investigates how organisms develop (from a single cell through an embryo to an adult body) to find out the ancestral relationships between organisms and how the processes of development evolved.

Subfields

The study of evolution is the unifying concept in evolutionary biology. Evolutionary biology is a conceptual subfield of biology that intersects with other subfields that are delimited by biological organisation level (e.g., cell biology, population biology), taxonomic level (e.g., zoology, ornithology, herpetology) or angle of approach (e.g., field biology, theoretical biology, experimental evolution, palaeontology). Usually, these intersections are combined into specific fields such as evolutionary ecology and evolutionary developmental biology.

History

Main article: History of evolutionary thought

The statistician Ronald Fisher (1890 – 1962) helped to form the modern evolutionary synthesis of Mendelian genetics and natural selection.

Evolutionary biology, as an academic discipline in its own right, emerged during the period of the modern evolutionary synthesis in the 1930s and 1940s (Smocovitis, 1996). It was not until the 1970s and 1980s, however, that a significant number of universities had departments that specifically included the term evolutionary biology in their titles, often in conjunction with ecology and behaviour. In the United States, as a result of the rapid growth of molecular and cell biology, many universities have split (or aggregated) their biology departments into molecular and cell biology-style departments and ecology and evolutionary biology-style departments (which often have subsumed older departments in botany, zoology and the like). The subdiscipline of palaeontology is often found in Earth science/geology/geoscience departments.

J. B. S. Haldane (1892 – 1964) helped to create the field of population genetics.

Microbiology has recently developed into an evolutionary discipline. It was originally ignored due to the paucity of morphological traits and the lack of a species concept in microbiology. Now, evolutionary researchers are taking advantage of a more extensive understanding of microbial physiology, the ease of microbial genomics, and the quick generation time of some microbes to answer evolutionary questions. Similar features have led to progress in viral evolution, particularly for bacteriophages.

Many biologists have contributed to our current understanding of evolution. Although the term had been used sporadically starting at the turn of the century, evolutionary biology in a disciplinary sense gained currency during the period of "the evolutionary synthesis" (Smocovitis, 1996). Theodosius Dobzhansky and E. B. Ford were important in the establishment of an empirical research programme for evolutionary biology as were theorists Ronald Fisher, Sewall Wright and J. S. Haldane. Ernst Mayr, George Gaylord Simpson and G. Ledyard Stebbins were also important discipline-builders during the modern synthesis, in the fields of systematics, palaeontology and botany, respectively. Through training many future evolutionary biologists, James Crow, Richard Lewontin, Dan Hartl, Marcus Feldman, and Brian Charlesworth have also made large contributions to building the discipline of evolutionary biology.

Current research topics

Current research in evolutionary biology covers diverse topics, as should be expected given the centrality of evolution to understanding biology. Modern evolutionary biology incorporates ideas from diverse areas of science, such as molecular genetics and even computer science.

First, some fields of evolutionary research try to explain phenomena that were poorly accounted for by the work of the modern evolutionary synthesis. These phenomena include speciation, the evolution of sexual reproduction, the evolution of cooperation, the evolution of ageing, and evolvability.

Second, biologists ask the most straightforward evolutionary question: "what happened and when?". This includes fields such as palaeobiology, as well as systematics and phylogenetics.

Third, the modern evolutionary synthesis was devised at a time when nobody understood the molecular basis of genes. Today, evolutionary biologists try to determine the genetic architecture of interesting evolutionary phenomena such as adaptation and speciation. They seek answers to questions such as how many genes are involved, how large are the effects of each gene, to what extent are the effects of different genes interdependent, what sort of function do the genes involved tend to have, and what sort of changes tend to happen to them (e.g., point mutations vs. gene duplication or even genome duplication). Evolutionary biologists try to reconcile the high heritability seen in twin studies with the difficulty in finding which genes are responsible for this heritability using genome-wide association studies.

Graphical representation of the modern "Tree of Life on the Web" project.

One challenge in studying genetic architecture is that the classical population genetics that catalyzed the modern evolutionary synthesis must be updated to take into account modern molecular knowledge. This requires a great deal of mathematical development to relate DNA sequence data to evolutionary theory as part of a theory of molecular evolution. For example, biologists try to infer which genes have been under strong selection by detecting selective sweeps.

Fourth, the modern evolutionary synthesis involved agreement about which forces contribute to evolution, but not about their relative importance. Current research seeks to determine this. Evolutionary forces include natural selection, sexual selection, genetic drift, genetic draft, developmental constraints, mutation bias and biogeography.

An evolutionary approach is also key to much current research in biology that does not set out to study evolution per se, especially in organismal biology and ecology. For example, evolutionary thinking is key to life history theory. Annotation of genes and their function relies heavily on comparative, i.e., evolutionary, approaches. The field of evolutionary developmental biology ("evo-devo") investigates how developmental processes work by using the comparative method to determine how they evolved.

Journals

Some scientific journals specialise exclusively in evolutionary biology as a whole, including the journals Evolution, Journal of Evolutionary Biology, and BMC Evolutionary Biology. Some journals cover sub-specialties within evolutionary biology, such as the journals Systematic Biology, Molecular Biology and Evolution and its sister journal Genome Biology and Evolution, and Cladistics.

Other journals combine aspects of evolutionary biology with other related fields. For example, Molecular Ecology, Proceedings of the Royal Society of London Series B, The American Naturalist and Theoretical Population Biology have overlap with ecology and other aspects of organismal biology. Overlap with ecology is also prominent in the review journals Trends in Ecology and Evolution and Annual Review of Ecology, Evolution, and Systematics. The journals Genetics and PLoS Genetics overlap with molecular genetics questions that are not obviously evolutionary in nature.

See also

• Artificial selection
• Comparative anatomy
• Computational phylogenetics
• Evolutionary computation
• Evolutionary dynamics
• Evolutionary neuroscience
• Evolutionary physiology
• Evolutionary psychology
• Genetics
• On the Origin of Species
• Phylogenetic comparative methods
• Quantitative genetics
• Selective breeding