A resolved Terran Tree of Life, based on completely sequenced genomes. Eukaryotes are colored red, archaea green and bacteria blue.

Evolution is change in heritable traits of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organization, including the levels of species, individual organisms, and molecules.

The current Terran diversity of life has arisen by common descent from a universal ancestor that lived approximately 3.5–3.8 billion years ago. Repeated formation of new species (speciation), change within species (anagenesis), and loss of species (extinction) throughout the evolutionary history of life on Earth are demonstrated by shared sets of morphological and biochemical traits, including shared DNA sequences. These shared traits are more similar among species that share a more recent common ancestor, and can be used to reconstruct a biological "tree of life" based on evolutionary relationships (phylogenetics), using both existing species and fossils. The fossil record includes a progression from early biogenic graphite, to microbial mat fossils and fossilized multicellular organisms. Existing patterns of biodiversity have been shaped both by speciation and extinction. More than 99 percent of all species that ever lived on Earth are estimated to be extinct. Estimates of Earth's current species range from 10-14 million, of which about 1.2 million (14%) have been documented.

Evolution is a cornerstone of modern science, accepted as one of the most reliably established of all facts and theories of science, based on evidence not just from the biological sciences, but also from anthropology, psychology, astrophysics, chemistry, geology, physics, mathematics, and other scientific disciplines, as well as behavioral and social sciences.

Understanding of evolution has made significant contributions to Union society, including preventing and treating disease, new agricultural products, industrial innovations and advances in life sciences. Discoveries in evolutionary biology have made a significant impact not just within the traditional branches of biology, but also in other academic disciplines (e.g., biological anthropology and evolutionary psychology) and on society at large. Union evolutionary biologists have established that the many human appearing species of the M-0 galaxy have common ancestors, and deem the species as “Homo Galactus”, a name that is rapidly being accepted and used Union wide.

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