Rewriting the story of humanity’s origins: Fossil records suggest our ancestors evolved right across Africa and not just in one region
- Experts found humans were not fully formed when they spread across the world
- Primitive skulls and bones of homo sapiens do not show a linear progression
- Instead the development is much more patchy from primitive to modern
- It took hundreds of thousands of years before all humans began to look as we do
For years, scientists believed that humans evolved in a single spot in Africa and this large band of people spread around the world.
It is as though there was a ‘Garden of Eden’, where humanity first began, before going forth and multiplying.
But a new study says the fossil record does not support humans being fully formed when they spread across the world.
Instead early humans had a huge variation in the sizes and shapes of their heads, undergoing a series of genetic and cultural shifts that led to modern humanity.
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A new study says the fossil record does not support humans being fully formed when they spread across the world. Left: African skull from around 300,000 years ago Right: Skull from the Levant dating from around 95,000 years ago
Primitive skulls and bones of homo sapiens do not show a linear progression from primitive to modern.
Instead the development is much more patchy – showing that it took hundreds of thousands of years before all humans began to look as we do today.
Studies of the DNA of modern day Africans – the most genetically diverse continent on Earth – paints a similar picture.
It shows human populations across the continent are so different they must have been separated for huge chunks of time.
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Scientists now suggest there must have been, multiple areas where different groups of humans developed different physical features.
These early bands of early humans then interbred over millennia. Only then did modern humans as we know them develop.
The fossil record suggests early homo sapiens were a patchwork quilt of different groups.
Dr Eleanor Scerri, an archaeologist at Oxford University, who led the international research, told The Guardian: ‘This single origin, single population view has stuck in people’s mind … but the way we’ve been thinking about it is too simplistic.’
The spread of humans led to local adaptation and development of unique primitive technologies. This image shows Middle Stone Age cultural artefacts from northern and southern Africa
Modern humans have small, slender faces, large round braincases, and chins.
If these features only evolved in one group of humans, we might expect to see a series of skulls going from larger to smaller faces, and gradually bigger, rounder braincases.
The fossil picture is much more complicated.
For example, skulls dating to 300,000 years ago found at Jebel Irhoud in Morocco – have small faces like modern humans.
But instead of a spherical braincase, theirs is long and elongated.
Meanwhile early human fossils dating more recently to 160,000 years ago – at Herto in Ethiopia – had big ‘robust’ faces – unlike us – but with ‘globular’ braincases like ours.
Professor Chris Stringer of the Natural History Museum and Dr Scerri have put forward the case in the journal Trends in Ecology and Evolution.
The authors said early humans were largely kept apart by a combination of diverse habitats and shifting environmental boundaries, such as forests and deserts.
Many of the most inhospitable regions in Africa today, such as the Sahara, were once wet and green, with interwoven networks of lakes and rivers, and abundant wildlife.
Designers used the fossils to recreate what they think the first Homo sapiens across Africa looked like 300,000 years ago. But the new research suggests early humans had a huge variation in the sizes and shapes of their heads
Similarly, some tropical regions that are humid and green today were once arid.
The shifting nature of these habitable zones meant human populations would have gone through many cycles of isolation.
This led to local adaptation and the development of unique primitive technologies – stone tools – and genetic makeup.
Professor Stringer pioneered the idea one big human population developed in Africa and spread worldwide – but now concedes this does not fit the facts.
He said when we look at human bones over the last 300,000 years ‘we see a complex mix of archaic and modern features in different places and at different times.
‘We do see a continental-wide trend towards the modern human form, but some archaic features are present until remarkably recently.’
When it comes to the development of stone tools, the pattern is also mixed.
Sometimes sophisticated tools appear further back in the fossil record, while cruder ones appear more recently – suggesting innovations occurred at different spots on the map at different times.
Prof Chris Stringer added: ‘Although I am one of the researchers who originally helped to develop the view that our species, Homo sapiens, had originated in Africa, I have increasingly come to the realisation that our African origin was a complex process.
‘The great diversity of African fossils between 200,000 and 400,000 years ago suggests that multiple lineages existed on the African continent at that time.’
This artist’s impression shows the patchwork of diverse fossils, artefacts and environments across Africa indicate that our species emerged from the interactions between a set of interlinked populations living across the continent, whose connectivity changed through time
Dr Scerri, said the stone tools discovered across Africa also don’t show a clear progression from crude to sophisticated.
She added that while there ‘is a continental-wide trend’ to greater sophistication over time, she said: ‘this ‘modernization’ clearly doesn’t originate in one region or occur at one time period.’
Professor Mark Thomas said the genetic patterns found in modern day Africans also support the idea.
He said: ‘It is difficult to reconcile the genetic patterns we see in living Africans, and in the DNA extracted from the bones of Africans who lived over the last 10,000 years, with there being one ancestral human population.’
Dr Scerri said: ‘The evolution of human populations in Africa was multi-regional. Our ancestry was multi-ethnic. And the evolution of our material culture was, well, multi-cultural.’
The full findings of the study were published in the journal Trends in Ecology & Evolution.
WHAT DO WE KNOW ABOUT HUMANKIND’S JOURNEY OUT OF AFRICA?
The traditional view
The traditional ‘Out of Africa’ model suggests that modern humans evolved in Africa and then left in a single wave around 60,000 years ago.
The model often holds once modern humans left the continent, a brief period of interbreeding with Neanderthals occurred.
This explains why individuals of European and Asian heritage today still have ancient human DNA.
There are many theories as to what drove the downfall of the Neanderthals.
Experts have suggested that early humans may have carried tropical diseases with them from Africa that wiped out their ape-like cousins.
Others claim that plummeting temperatures due to climate change wiped out the Neanderthals.
The predominant theory is that early humans killed off the Neanderthal through competition for food and habitat.
How the story is changing in light of new research
Recent findings suggest that the ‘Out of Africa’ theory does not tell the full story of our ancestors.
Instead, multiple, smaller movements of humans out of Africa beginning 120,000 years ago were then followed by a major migration 60,000 years ago.
Most of our DNA is made up of this latter group, but the earlier migrations, also known as ‘dispersals’, are still evident.
This explains recent studies of early human remains which have been found in the far reaches of Asia dating back further than 60,000 years.
For example, H. sapiens remains have been found at multiple sites in southern and central China that have been dated to between 70,000 and 120,000 years ago.
Other recent finds show that modern humans reached Southeast Asia and Australia prior to 60,000 years ago.
Based on these studies, humans could not have come in a single wave from Africa around this time, studies have found.
Instead, the origin of man suggests that modern humans developed in multiple regions around the world.
The theory claims that groups of a pre-human ancestors made their way out of Africa and spread across parts of Europe and the Middle East.
From here the species developed into modern humans in several places at once.
The argument is by a new analysis of a 260,000-year-old skull found in Dali County in China’s Shaanxi Province.
The skull suggests that early humans migrated to Asia, where they evolved modern human traits and then moved back to Africa.
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