![]() Earliest development of bilateral symmetry, mesoderm, head (anterior cephalization) and various gut muscles (and thus peristalsis) and, in the Nephrozoa, nephridia (kidney precursors), coelom (or maybe pseudocoelom), distinct mouth and anus (evolution of through-gut), and possibly even nerve cords and blood vessels. Xenacoelomorphs all have a gonopore to expel gametes but nephrozoans merged it with their anus. The last common ancestor of xenacoelomorphs, protostomes (including the arthropod, mollusc and annelid lineages) and the deuterostomes (including the vertebrate lineage) (the last two are more related to each other and called Nephrozoa). Diploblasts separated their early embryonic cells into two germ layers ( ecto- and endoderm). Planulozoa/ ParaHoxozoa: separation from the Placozoa and Cnidaria lineages.Īll diploblasts possess epithelia, nerves, muscles and connective tissue and mouths, and except for placozoans, have some form of symmetry, with their ancestors probably having radial symmetry like that of cnidarians. Separation from the Porifera ( sponges) lineage.Įumetazoa/ Diploblast: separation from the Ctenophora ("comb jellies") lineage. Multicellular animals may have existed from 800 Ma. These fossils are interpreted as being early sponges. The first fossils that might represent animals appear in the 665-million-year-old rocks of the Trezona Formation of South Australia. They live in colonies, and show a primitive level of cellular specialization for different tasks.ĭickinsonia costata from the Ediacaran biota, 635–542 Ma, a possible early member of Animalia. Proterospongia (members of the Choanoflagellata) are the best living examples of what the ancestor of all animals may have looked like. The Holozoa lineage of eukaryotes evolves many features for making cell colonies, and finally leads to the ancestor of animals (metazoans) and choanoflagellates. Sexual reproduction evolves ( mitosis and meiosis) by this time at least, leading to faster evolution where genes are mixed in every generation enabling greater variation for subsequent selection. Genus Homo and close human relatives and ancestors after splitting from Pan-the homininsįurther information: Eukaryote § Origin of eukaryotes Includes both Homo, Pan (chimpanzees), but not Gorilla. Humans, chimpanzees, and gorillas (the African apes) Great apes: humans, chimpanzees, gorillas and orangutans-the hominids "Downward-nosed" primates: apes and old-world monkeysĪpes: great apes and lesser apes ( gibbons) "Dry-nosed" (literally, "simple-nosed") primates: tarsiers and monkeys (incl. Supraprimates: primates, colugos, tree shrews, rodents, and rabbits Supraprimates, (most) hoofed mammals, (most) carnivorous mammals, cetaceans, and bats Mammals that give birth to live young (i.e., non-egg-laying) Limbs beneath the body and other mammalian traits Holozoa + Holomycota (Cristidicoidea and Fungi)Ĭhordates (Vertebrates and closely related invertebrates)Īmniotes (fully terrestrial tetrapods whose eggs are "equipped with an amnion") In cases of open questions with no clear consensus, the main competing possibilities are briefly outlined.Ī tabular overview of the taxonomic ranking of Homo sapiens (with age estimates for each rank) is shown below. The timeline reflects the mainstream views in modern taxonomy, based on the principle of phylogenetic nomenclature It includes brief explanations of the various taxonomic ranks in the human lineage. sapiens during and since the Last Glacial Period. Throughout the history of life, beginning some 4 billion years ago down to recent evolution within H. The timeline of human evolution outlines the major events in the evolutionary lineage of the modern human species, Homo sapiens, While Haeckel's tree is outdated, it illustrates clearly the principles that more complex and accurate modern reconstructions can obscure. The evolutionary history of species has been described as a " tree" with many branches arising from a single trunk. Chronological outline of major events in the development of the human species Haeckel's Paleontological Tree of Vertebrates (c. 1879).
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