Neanderthals (; German: [neˈ(ʔ)andɐtaːl]; Homo neanderthalensis or Homo sapiens neanderthalensis), alternatively spelt as "Neandertals", are an extinct species or subspecies of archaic humans who lived within Eurasia from circa 400,000 until 40,000 years ago.
Currently the earliest fossils of Neanderthals in Europe are dated between 450,000 and 430,000 years ago, and thereafter Neanderthals expanded into Southwest and Central Asia. They are known from numerous fossils, as well as stone tool assemblages. Almost all assemblages younger than 160,000 years are of the so-called Mousterian techno-complex, which is characterised by tools made out of stone flakes. The type specimen is Neanderthal 1, found in the Neander Valley in the German Rhineland, in 1856.
Compared to modern humans, Neanderthals were stockier, with shorter legs and bigger bodies. These are often explained as adaptations to conserve heat in a cold climate, but these could also be adaptations for sprinting in a warmer, forested landscape which they seemed to have preferred based on fossil distribution. Male and female Neanderthals had cranial capacities averaging 1,600 cm3 (98 cu in) and 1,300 cm3 (79 cu in), respectively, within the range of the values for anatomically modern humans. Average males stood around 164 to 168 cm (5.4 to 5.5 ft) and females 152 to 156 cm (5.0 to 5.1 ft) tall.
There has been growing evidence for admixture between Neanderthals and anatomically modern humans, reflected in the genomes of all modern non-African populations but not in the genomes of most sub-Saharan Africans. The proportion of Neanderthal-derived ancestry is estimated to be around 1–4% of the modern Eurasian genome. This suggests that some interbreeding between Neanderthals and anatomically modern humans took place after the recent "out of Africa" migration of around 50-70,000 years ago. Recent admixture analyses have added to the complexity, finding that Eastern Neanderthals derived up to 2% of their ancestry from an earlier wave of anatomically modern humans who left Africa some 100,000 years ago.