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innovative humankind ( Homo sapiens ) are the sole come through representatives of thehuman household tree , but we ’re the last prison term in an evolutionary story that began approximately 6 million years ago and spawned at least 18 mintage know collectively as hominins .
There were at least nineHomospecies — includingH. sapiens — distributed around Africa , Europe and Asia by about 300,000 years ago , harmonise to the Smithsonian’sNational Museum of Natural Historyin Washington , D.C. One by one , all exceptH. sapiensdisappeared . Neanderthalsand aHomogroup known as theDenisovanslived alongsideH. sapiensfor G of years , and they even interbreed , as evidence by bits of their desoxyribonucleic acid that linger in many people today . But eventually , the Denisovans and the Neanderthals also disappear . By around 40,000 years ago , H. sapienswas the last hominin leave alone .
Reproductions of skulls from a Neanderthal (left), Homo sapiens (middle) and Australopithecus afarensis (right)
So what was the secret to our success ? Why didH. sapienssurvive when all of our congenator went extinct ?
To sympathize how we endured as a metal money , we must first search at what we have in mutual with other hominins , saidWilliam Harcourt - Smith , a paleoanthropologist at Lehman College and the American Museum of Natural History , both ground in New York City . top that list is bipedalism . Two - legged walking originated in theArdipithecusgroup — our earliest human ascendent who lived around 4.4 million years ago — andAustralopithecus , which appeared about 2 million years after . Both group were " little more than bipedal apes " with relatively small brains , Harcourt - Smith told Live Science .
Bipedalism was an of import evolutionary step for hominins , but it did n’t stave off defunctness forArdipithecus , Australopithecusand a third hominin genus — Paranthropus . Australopithecusemerged asArdipithecuswas disappearing;Paranthropusand the firstHomospecies appear in Africa about 3 million yr ago , asAustralopithecuswas dying out .
Reproductions of skulls from a Neanderthal (left), Homo sapiens (middle) and Australopithecus afarensis (right)
Unlike emergingHomospecies , which had bigger brainpower and smaller teeth than their predecessors , Paranthropushad small mental capacity and were more apelike , with monumental back tooth and powerful masticate muscle , Harcourt - Smith said .
" For quite a tenacious time , you ’ve gotHomoandParanthropusoccupying peradventure different niches but standardized landscapes , and they both do really well , " Harcourt - Smith said . But after about 1 million days , Paranthropuswas gone , and " Homohangs on and proliferates , eventually across the world , " he said .
What extinguishedArdipithecus , AustralopithecusandParanthropus ? " Nobody hump for sure , and it probably was n’t just one thing , " saidElizabeth Sawchuk , associate conservator of humanevolutionat the Cleveland Museum of Natural History .
" Potential factors let in environmental change , competition for food and resources between contemporaneous hominin species , and small population density , " she told Live Science in an email .
heavy learning ability inHomocertainly gave the genus an boundary overParanthropus , Harcourt - Smith added . With larger brains came betterment in cognition and toolmaking abilities , more behavioral flexibility , increase sociality and better problem - resolution .
" They were likely in moderately complex crime syndicate group ; perhaps they wereburying their utter . They were building shelter ; they were making rocket artillery ; they had thecontrolled consumption of fire , " he tell . " You get down to see the emergence of specialization , dissimilar tools for different tasks . They were engaging with the landscape in sophisticated ways . "
This may have madeHomospecies more bouncy and adaptable thanParanthropuswas , but untangle what madeH. sapiensoutlast all otherHomospecies is cunning . Ancient tools , art and other artifact suggest that our cognitive powers , technical prowess and problem - solving were more advance than those of our close relative , Harcourt - Smith enjoin . flexile societal scheme also could have helpedH. sapienspersist where other specie perished , Sawchuk suggested .
" As a coinage , our flexibility has help us well , " Sawchuk said . " One of the reasons we ’ve been able to spread out so effectively is that we ’ve watch to adapt to a variety of environments — not just biologically , but alsoculturallythrough our engineering and behaviour . "
Another factor could simply be chance , Harcourt - Smith added . humble specie populations can swiftly crash come after natural disasters , disease outbreaks or climate shifts , lead a formerly fill niche open for other species to take over .
" Serendipity is part of it , " he tell . " You ’ve bring to be in the right blank space at the correct time . "
Flexible and competitive
homosexual erectuswas the firstHomospecies to appear , spreading across Africa and into eastern Asia . Over hundreds of thousands of years , more species followed : Homo heidelbergensis , Homo naledi , Homo floresiensisandHomo luzonensis , as well asH. sapiens , Neanderthals and Denisovans .
Related : Will humans ever be immortal ?
After emerging in Africa , H. sapiensmigrated into Europe , where Neanderthals were already found , and into Asia , where they run into Denisovans . Evidence fromDNA in the great unwashed today bear witness that these groups interact , and it ’s potential thatH. sapiensoutcompeted and overwhelmed these groups — and possiblyotherHomospeciesthat are yet to be identified .
" While we do n’t know what part we play in their extinction , it seems likely that our spread out of Africa put stress on other species through competition for resources , " Sawchuk said . " Our coinage was very successful at moving around and conjugation , which is belike one of the understanding we ’re still here . "
Globalclimate changeis also consider to have conduce to the extermination of someHomospecies , " but it ’s hard to say how much of a role it play , " Sawchuk aver . " For example , our speciesHomo sapiensevolved in Africa but survived theIce Agesin Europe whereas Neandertal man , who were accommodate to cold conditions , did not . It stand to reason that there was more to the equation than just climate . "
— Could climate variety make human beings go extinct ?
— How would Earth be dissimilar if modern humans never survive ?
— When humans are sound , what fauna might evolve to have our smarts and skills ?
In the final stage , what doomed ourHomorelatives " was probably a combination of factors , " Sawchuk said , " with a snatch of random chance . "
As it happens , H. sapienscame perilously close to extinguishing at one point . Arecentgenetic analysisof more than 3,000 multitude in African and non - African groups revealed lower genetic diversity than expected . Scientists trace this to abreeding " bottleneck"between 813,000 and 930,000 years ago , with the globalHomopopulation hovering at roughly 1,300 for more than 100,000 year .
" It ’s important to remember that our selection is n’t assured , " Sawchuk said . " Falling back on our flexibility and concerted skills will serve us well as we face new challenges . "
