Changes in structure and function over successive generations (or across geological time) as a result of a number of mechanisms. These changes may lead to new adaptations within an existing population (microevolution) or those that constitute speciation or extinction (macroevolution). One interpretation is that the changes are a gradual accumulation of small, favourable alterations due to natural selection acting on variability in phenotypes created by point mutations in genes and by genetic recombination (phyletic gradualism). This is the view espoused by the Modern synthesis. An alternative, and more controversial but older, interpretation (punctuated equilibrium) is that change is more saltatory or catastrophic, and thus accounts for macroevolution in a more convincing way than the Modern synthesis. While it does not deny the mechanisms upon which the Modern synthesis rests, it stresses as well the roles of random genetic drift in isolated populations and the possibility of mutations in whole chromosomes as causal agents in evolutionary change. Enduring debates about the nature of biological evolution include, for example, the mechanisms of speciation and how it might relate to cultural evolution. Debates aside, biological evolution continues to have a continuing fascination for the general public. It was perhaps the poet and playwright Louis MacNeice (1907-1963) who captured its enduring attraction and mystery in his book Zoo (1938) as follows: “The pleasure of dappled things, the beauty of adaptation to purpose, the glory of extravagance, classical elegance or romantic nonsense or grotesqurerie.”
See Adaptation, Convergent evolution, Cultural evolution, Cultural evolution and biological evolution, Evolution, Founder effect (or principle), Genetic drift (or random walk), Genetic (or DNA) recombination, ‘Hopeful’ monsters, Macroevolution (horizontal evolution) and microevolution (or vertical evolution, Modern synthesis, Mutation (biology), Phyletic gradualism and punctuated equilibrium, Phylogeny, Population (biology and ecology), Speciation, Theory of natural selection