Curated by RSF Research Staff
Homo sapiens Direct Ancestors Migrated Out of Africa 2 million years ago
There has been a constant stream of discoveries in the last twelve months which suggest a need to move back the dates for our early ancestor’s migration out of Africa. Modern human fossils uncovered in Asia, as well as new DNA studies, have pushed back the occupation of that continent from 60,000 to 120,000 years ago. Stone tools and hominin fossils discoveries suggest that archaic Homo sapiens inhabited parts of Eurasia well before 200,000 years ago, at least 300,000 to 400,000 years ago.
These suggested revisions to the human story may sound quite major, but they are extremely conservative considering the greater body of evidence available. There is a good reason to believe our early ancestors migrated out of Africa 2,000,000 years ago, for some peculiar reason the public almost never hears about this in the mass media. It may at first sound so extreme that it must be a fanciful revision, but it is incredibly reasonable and supported by a wealth of sound scientific evidence.
“It was not until around 2 million years ago that human ancestors first migrated out of Africa and spread throughout the Old World.” – Rolf Quam, Associate Professor of Anthropology, Binghamton University, State University of New York
Today scientists almost unanimously believe that modern humans can trace their origins back to a population of hominins that appeared in the African fossil record around 2 million years ago, Homo ergaster. That Homo ergaster is our direct ancestor has never been established for certain, and there has always been a second strong contender, Homo erectus. We know that Homo erectus and Homo ergaster were once part of a single population, 2 million years ago they were simply two regionally separated populations within a single species.
Homo erectus did something that no other hominin before it had managed, it conquered the planet. Today fossils place members of this hominin species at sites as disparate as the Georgian Republic and Indonesia as early as 1.8 million years ago. Groups of Homo erectus made their way into almost all habitable regions in the hundreds of millennia which followed this initial expansion, a few skull fragments in America have even been claimed as evidence they were the first to reach that continent (though such claims remain highly contested).
Changes in environment or climate are understood to be the primary drivers of evolutionary adaptation, just as a need is the mother of innovation. Homo erectus would have faced incredible challenges as it moved into alien environments beyond the African continent. These intrepid explorers would have encountered unknown animals, many of them dangerous predators, explored unfamiliar landscapes such as icy tundra, deserts, tropical rainforests and coastlines while passing through a wide range of climates. Their survival would have been dependant on flexible thinking, innovation and rapid adaptation. When you apply basic logic, it seems obvious that Homo erectushad entered the evolutionary fast lane by exiting the familiar and relatively static environment within the African motherland.
Meanwhile, back in Africa, Homo ergaster would have been under little pressure to change, being highly adapted to the African landscapes and climate the forces responsible for human evolution would have been running in a low gear, restricted to at most negligible levels. Evolutionary changes would still inevitably occur for these hominins, but there is little reason to think it would have occurred rapidly or produced any profound modifications. There are numerous examples of well-adapted organisms in almost static environments that have barely changed over millions of years.
You are almost certainly wondering why academics favour the stay-at-home stick-in-the-mud Homo ergaster as a prime candidate for our Homo sapiens ancestor, rather than the dynamic and entrepreneurial Home erectus.
The decision to favour Homo erectus’s African cousin was based largely on assumptions, as hominins appeared first in Africa and evolved into new forms there over millions of years and the earliest definitively Homo sapiens fossils were found within that continents boundaries, it was assumed they evolved there from earlier hominins. There was, of course, a huge time gap between Homo ergasterand the emergence of Homo sapiens, there was also an enormous change in the morphology (physical form) during that separating period. The scientists needed fossils representing a series of transitional human forms that would connect these two populations.
With the discovery of Homo heidelbergensis, it seemed that the missing link, or one of them, had finally been uncovered. Sometime around 600,000 years ago, this large brained hominin named Homo heidelbergensis appeared in the fossil record across Africa, Europe and Asia. With a strong contender for a direct, immediate ancestor of Homo sapiens identified in Africa the case for an Out of Africa Homo sapiens model seemed almost certain. It seemed only a matter of time before an earlier hominin would be found that linked Homo heidelbergensis to Homo ergaster. That was of course until the best contender for Homo sapiens ancestor was knocked out.
Research revolving around a large collection of hominin fossils in Northern Spain (Sima de los huesos) has revealed that Homo heidelbergensis emerged after the split between the ancestors of modern humans and those of Neanderthals, with Homo heidelbergensis being exclusively an early form of Neanderthal. There are now no fossils representing a viable ancestor for modern humans anywhere in Africa earlier than 300,000 years ago. We also lack evidence of the evolutionary transition between Homo ergaster and Neanderthals, or Denisovans, in the African record.
When you put all this information together and apply logical deduction, the existing evidence points towards all three large brained hominin lineages emerging from Homo erectus somewhere far from Africa, perhaps East Asia. Sporadic migrations of transitional human forms gradually brought these populations into Africa in waves as climate changes drove them towards preferential locations. While Africa suddenly has a glaring lack of suitable transitional fossils, East Asian scientists are announcing a growing list of potential candidate finds.
“The tale is further muddled by Chinese fossils analysed over the past four decades, which cast doubt over the linear progression from African H. erectus to modern humans. They show that, between roughly 900,000 and 125,000 years ago, east Asia was teeming with hominins endowed with features that would place them somewhere between H. erectus and H. Sapiens.” Wu Xinzhi, palaeontologist at the Chinese Academy of Sciences’ Institute of Vertebrate Paleontology and Paleoanthropology
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