Tracing a direct line of ancestry back along this branch is difficult because the fossil record is a patchy mosaic of incomplete skeletons. Few early humans died at the right time and place for their remains to be preserved. Entire species probably became extinct without leaving a single toe bone for us to dig up in the smattering of places we are looking.
Our earliest Homo ancestors most likely descended from Australopithecus afarensis , best known for the 3. A jawbone found in Ledi-Geraru, also in the Afar — marks the debut of Homo in the fossil record at 2. By the time the fossil record begins to pick up around two million years ago, there were at least three early Homo species loping around Eastern Africa — Homo habilis , Homo rudolfensis , and Homo erectus.
What drove this early radiation is not clear, although many point to a changing climate — a common precursor to species booms. As East Africa dried around 2. Homo habilis , with its prominent snout, was the most primitive looking of the three. Although stone tools dating back to 3. For a long time, Homo habilis fit the bill as one of our direct relatives. Homo habilis was an early side-branch, possibly splitting off from the 2.
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Homo rudolfensis was a later offshoot, while Homo erectus — as we shall see — has assumed a central position in the story of human evolution over the last two million years. All Homo species that crop up later than two million years ago — including us — are thought to have Homo erectus as their forebear.
It was tall — up to cm — with long legs, short arms, and a larger brain than its predecessors. It made hand axes and mastered the use of fire. Homo erectus was also the first to venture out from its African homeland. Early Homo erectus fossils sometimes referred to as Homo ergaster first appeared in East Africa around two million years ago. In Asia, Homo erectus gave rise to at least one species: Homo floresiensis , a dwarfed early human that lived on the Indonesian island of Flores 60—, years ago.
Older floresiensis -like fossils, also on Flores, date to , years ago and stone tools on the island to one million years ago. Whether Homo erectus made it into Western Europe is unclear — certainly no fossils have been found to suggest they did. But by about 1.
How did we get here? Where did we all come from?
Meanwhile, Homo erectus was busy colonising much of the African continent. Homo naledi , whose as-yet-undated remains were plucked from a cave system in South Africa, is one possible descendant. Homo erectus was also spawning lineages that definitely did traipse into Western Europe, and others that would go on to become the globetrotting modern humans. One of these descendants — Homo heidelbergensis — was the second species after Homo erectus to migrate out of Africa after it evolved probably first as Homo rhodesiensis. But most remains show it spreading north and west into the colder climes of Europe, including Great Britain, thanks in part to its stocky build.
Homo heidelbergensis was a skilled hunter — it made spears to fell large game such as horses and elephants — and was the first to build simple shelters. Two important lineages come from Homo heidelbergensis : an African lineage leading to modern humans, and a European line that leads to Neanderthals Homo neanderthalensis , Denisovans and possibly other species that were contemporaries of early Homo sapiens. Neanderthals were the first on the scene: the oldest remains put their emergence back at around half a million years ago. From their European homeland, they moved east as far as Siberia in Central Asia, but never crossed into Africa.
Neanderthals were a sophisticated bunch. They hunted large game, plucked fish, molluscs and dolphins from the seas, and possibly sewed rudimentary animal-hide clothing using large bone needles. They also constructed mysterious rock structures in underground caves, but no one knows why. Ultimately, however, Neanderthals became extinct around 40, years ago, although they may have held on as late as 28, years ago in southern Spain.
Homo sapiens , like our Homo heidelbergensis and Homo erectus ancestors before us, evolved in Africa — around , years ago — and then travelled north into Eurasia. Most current accounts, drawn from the fossil record and studies of both ancient and modern human DNA, suggest that they did this not once, but twice. The first migration had Homo sapiens reaching the Middle East , years ago, and China as early as 80, years ago.
Homo sapiens rapidly dispersed into Europe and Asia, reaching Australia by 55, years ago, and the Americas , years ago. For decades, the demise of Neanderthals in Europe was chalked up to the arrival of the more competitive — or downright bloodthirsty — Homo sapiens. But the advent of ancient DNA analysis over the last decade has shaken up this tidy version of history. By cajoling ancient DNA from millennia-old fossils, palaeogeneticists have uncovered a more intriguing tale of interspecies trysts: humans with Neanderthals, Neanderthals with Denisovans, Denisovans with humans, and possibly others.
"Where did we come from, Mommy?"
Sequencing of the Neanderthal genome from Croatian remains in revealed the first evidence that humans and Neanderthals mated. The first encounter probably occurred in the Middle East around 50, to 60, years ago, as Homo sapiens migrated out from Africa.
Later matings in Eastern Europe and Asia have been proposed, and an earlier Middle Eastern encounter between Neanderthals and the first wave of human migrants also took place. Humans also interbred with the Denisovans, a group known from limited remains — a finger bone and a few teeth — recovered from a Siberian cave and dating to around , years ago.
Primates and then apes are thought to have appeared in the last million years. Two-footed apes came along about seven million years ago, upright but possibly still tree swingers. The first human or homo species, three million years ago - no more tree swinging and it includes homo erectus, Neanderthals and now homo naledi as well as up to 20 other known species.
Us, or homo sapiens, modern humans, appeared just , years ago, a mere fleck of evolutionary time.
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The traditional view is that by the time we evolved, other human species were mostly extinct and that's because we, homo sapiens, were smarter. We had better weapons, we had language, we had culture.
In short, we were obviously superior. Well, turns out, that might be wrong.
Origins – Where Did We Come From?
A year before homo naledi was discovered, Darren Curnoe from the University of New South Wales with Chinese colleague Ji Xueping found another new human species in Southwest China, as featured in the electric pictures documentary Enigma Man. The so-called Red Deer Cave people from the Yunnan Province also look like ancient cousins who were extinct long before we appeared, but the fossils date to just 13, years ago, meaning they may have co-existed with modern humans for tens of thousands of years. So when you add up the other human species known to have crossed over with modern humans like the Red Deer Cave people and the Neanderthals as well as recent discoveries of others like the Denisovans found in Siberia and the tiny hobbits found in Indonesia, it starts to feel like the Planet of the Apes.
In fact if I speculate, I would imagine that there are probably going to be dozens of more discoveries of new species over the next sort of perhaps 50 years.
Some experts believe that all these so-called other species like Neanderthals are actually just us, another variety of homo sapiens, which leaves the evolutionary ladder intact. OF ADELAIDE: Interpretations of those findings differ between various scholars or researchers and those differences range from labelling practically each new find a new species, so give it a specific status, to interpretation that simply says: all those finds fit into the general stream of human evolution.
Now we know that it was not so. At first I was amazed. Maybe there were periods of co-existence, there was probably warfare, but recent genetic testing proves there was also interbreeding. About 30 per cent of the Neanderthal genome lives on in non-Africans, each person carrying up to four per cent.
Geneticists have also found some of us carry DNA from as-yet-unidentified archaic human species. So all of us carry at least some ghost DNA from these long lost species, their living fossils inside us. Neanderthals are thought to have given modern humans red hair and improved immunity.
Denisovans gave Tibetans the gene to survive high altitudes in the Himalayas. Such unexpected intimacy and diversity in our evolutionary story begs the question: were we so different from them? Why were we the only species to survive?
Some of those other species lasted maybe two million years or more. Why did they disappear? They've gone. Just us today. Were we really special or just incredibly lucky?
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