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The varying definitions of sympatric speciation fall generally into two categories: definitions based on biogeography, or on population genetics. As a strictly geographical concept, sympatric speciation is defined as one species diverging into two while the ranges of both nascent species overlap entirely – this definition is not specific ...
The timeline of human evolution outlines the major events in the evolutionary lineage of the modern human species, Homo sapiens, throughout the history of life, beginning some 4 billion years ago down to recent evolution within H. sapiens during and since the Last Glacial Period.
There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric, peripatric, parapatric, and sympatric. Whether genetic drift is a minor or major contributor to speciation is the subject of much ongoing discussion.
Anatomically modern humans appear in Africa. [103] [104] [105] Around 50 ka they start colonising the other continents, replacing Neanderthals in Europe and other hominins in Asia. 70 ka Genetic bottleneck in humans (Toba catastrophe theory). 40 ka Last giant monitor lizards (Varanus priscus) die out. 35-25 ka Extinction of Neanderthals.
The aquatic ape hypothesis (AAH), also referred to as aquatic ape theory (AAT) or the waterside hypothesis of human evolution, postulates that the ancestors of modern humans took a divergent evolutionary pathway from the other great apes by becoming adapted to a more aquatic habitat. [1]
The first fully terrestrial vertebrates were reptilian amniotes — their eggs had internal membranes that allowed the developing embryo to breathe but kept water in. This allowed amniotes to lay eggs on dry land, while amphibians generally need to lay their eggs in water (a few amphibians, such as the common Suriname toad, have evolved other ways of getting around this limitation).
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
The hominoids are descendants of a common ancestor.. Homo sapiens is a distinct species of the hominid family of primates, which also includes all the great apes. [1] Over their evolutionary history, humans gradually developed traits such as bipedalism, dexterity, and complex language, [2] as well as interbreeding with other hominins (a tribe of the African hominid subfamily), [3] indicating ...