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Two species are described in the literature: A. ramidus, which lived about 4.4 million years ago [32] during the early Pliocene, and A. kadabba, dated to approximately 5.6 million years ago [33] (late Miocene). A. ramidus had a small brain, measuring between 300 and 350 cm 3.
[2] [3] Estimates on the number of Earth's current species range from 10 million to 14 million, [4] with about 1.2 million or 14% documented, the rest not yet described. [5] However, a 2016 report estimates an additional 1 trillion microbial species, with only 0.001% described.
Although earlier dispersals had occurred, probably over water, the migration accelerated dramatically about 2.7 million years ago during the Piacenzian age. [1] It resulted in the joining of the Neotropic (roughly South American) and Nearctic (roughly North American) biogeographic realms definitively to form the Americas.
[4] And: "The primary competing scientific hypothesis is currently recent African origin of modern humans, which proposes that modern humans arose as a new species in Africa around 100-200,000 years ago, moving out of Africa around 50-60,000 years ago to replace existing human species such as Homo erectus and the Neanderthals without interbreeding.
The genus Australopithecus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct 2 million years ago. During this time period various forms of australopiths existed, including Australopithecus anamensis, A. afarensis, A. sediba, and A. africanus.
Map of early human migrations based on the Out of Africa theory; figures are in thousands of years ago (kya). [1]The peopling of the Americas began when Paleolithic hunter-gatherers (Paleo-Indians) entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the ...
The ancestors of the modern Khoi-San expanded to Southern Africa before 150,000 years ago, possibly as early as before 260,000 years ago, [note 5] so that by the beginning of the MIS 5 "megadrought", 130,000 years ago, there were two ancestral population clusters in Africa, bearers of mt-DNA haplogroup L0 in southern Africa, ancestral to the ...
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 ...