Out of Africa

"The conventional timeline of human evolution and migration continues to crumble in the face of new research."
Gemma Tarlach, science writer, Discover Magazine

"That's just because of the way that the differences can accrue over time between the genetic lineage and the species, right? You're always going to have individuals and populations within a species that go extinct and leave no living descendants."
"So they represent basically lost lineages of people leaving Africa, and their descendants slowly expanding into parts of Europe and Asia, but then for whatever reason, those populations went extinct. And subsequently, somewhere around 40,000 to 70,000 years ago, we have groups of modern humans beginning to leave Africa again, and they're essentially the ancestors of all of us that are of non-African descent."
"The context of that find really challenged people's thinking, but now, 15 years later, it's not as challenging, because we really see this process of dispersal happening again and again for the past two million years."
"So likely Homo Florsiensis represents descendants of some of those earliest dispersals of humans out of Africa, long before even the common ancestors of humans and Neanderthals evolved and left Africa."
"[The signal of Neanderthal in modern non-African human DNA is] rather small, and there have been clear selective sweeps against Neanderthal DNA in our DNA. So what that means is essentially it wasn't really as compatible as any other two populations of modern humans breeding together." 
"The fact that [the Jebel Irhoud bones] date to that [early] time pretty much excludes them as a potential ancestor of anyone living today."
Matthew Tocheri, anthropologist, Canada Research Chair in Human Origins, Lakehead University

"The common myth that we drove them [Neanderthals] to extinction is just that, it's a myth."
"There's no evidence at all in the archaeological or fossil record of modern humans interacting with Neanderthals."
"There is no way to know from what part of that population [in Europe and Asia] the first modern humans did so [left Africa]."
David Begun, paleoanthropologist, University of Toronto

Two views of a composite reconstruction of the earliest known Homo sapiens fossils from Jebel Irhoud (Morocco) based on micro computed tomographic scans of multiple original fossils.

Philipp Gunz, MPI EVA Leipzig

At one time the scientific hypothesis called the multi-regional theory held that modern humanity resulted from an evolutionary process over the space of two million years taking place simultaneously in archaic human populations existing in Africa, Europe and Asia. That theory eventually surrendered to the more probable one that human origin could be traced to its beginnings in East Africa. More recent studies indicate that human and Neanderthal evolution diverged 500,000 years ago, scant Neanderthal DNA remaining in the human genetic code, of less than five percent.

The view that humans of today all share their origins from a small group of East African ancestors resulting in all of humanity essentially stemming from the same family tree and sharing an attractively theorized grandmother named Mitochondrial Eve, was seen as a great anthropological leveller; that we evolved as a single race. That the Caucasus did not produce Caucasians and nor did Asians originate in Asia; we all evolved from the original East African strain of humanity.

And the human record, thanks to new  strides in genetics and fossils along with biomechanics has led paleoanthropologists to believe humans as a species are older than believed to have been the case.

That the human species 'left' Africa on many occasions over the anthropological time record, evolving in different regions at variant rates, not in one fell swoop of an immense migration in a finite period of time. The Neanderthals and the littler-known Denisovans appeared, according to this new agreement between scientists, to have died out on their own, similarly to every other hominin population that once lived, with the exception of Homo sapiens.

The previously-subscribed-to timeline went back to 200,000 years earlier in East Africa when a small population of Homo sapiens, anatomically modern, having descended from an ape became behaviourally 'modern' in the last 100,000 years, colonizing the entirety of Africa, moving to the Middle East, Europe, Asia and in time, North and South America. An increasingly consistent fossil record of manufactured tools and a progression of artwork helped to tell the story of emerging conceptual thought.

The romance of the Great Rift Valley as the cradle of evolutionary humankind was the locus encouraging the shaping of the human mind and body and where the four "Fs" of evolution emerged: fighting, fleeing, feeding and mating. That is, in the popular imagination of paleontologists of the time. What has remained constant, however, while research advances a more accurate understanding of evolution is that origins in Africa remain certain, even though the scope has been recognized as somewhat more complicated.

The Moroccan hillside where anthropologists found the remains.

Shannon McPherron, MPI EVA Leipzig

In June, a discovery reported in Nature initiated a wholesale re-think when bones from a site called Jebel Irhoud in Morocco, thought to represent Neanderthals, were later identified as human when additional bones were unearthed, augmented by an improvement in scientific dating techniques of the sedimentary layer in which they were discovered, shown to be up to 350,000 years in primitive antiquity. The traditional story of evolution underwent a transformation reflecting the presence of anatomically modern Homo sapiens in Morocco dating that far back.

The lead taken from that discovery was that the emergence of humanity was not confined to a certain East African savanna, more in all likelihood the entire continent of Africa, representing a full fifth of the planet's land mass. Most of those human populations, it seems, simply failed to survive. Similar discoveries have been unearthed in Europe with genetic combinations no longer existing in modern humans, indicating a pattern of ancient humans migrating out of Africa and in so doing becoming isolated and in time, extinct, leaving behind a fossil record.

Fossils discovered in Indonesia in 2003 known as Homo Floresiensis represent one example; those discovered in Indonesia overlapping with the fossils of modern humans as little as a few thousand years ago created a conundrum for anthropologists. That they simply failed to survive as a species lends a new air of discovery relating to Neanderthals as well, dispelling the long-held theory that the superior Homo sapiens involved in conquest of a challenger for resources, exterminated Neanderthals.

This is a schematic representation of the evolutionary scenario for mitochondrial and nuclear DNA in archaic and modern humans. Neanderthal mitochondrial DNA recovered in this study suggests an intermediate migration out of Africa before 220,000 years ago.

Credit: Annette Günzel, © Max Planck Institute for the Science of Human History