Que tal de donde todos vinimos!!!!!
- Scientists sequenced 300 genomes from 142 small ethnic populations
- Analysis showed all living humans descend from a single group in Africa
- Non-Africans split from African hunter gatherers 130,000 years ago
- Several groups in Africa also appear to have split and become isolated
There are an estimated 7.4 billion people around the globe, but every human living today can trace their genes back to a single group who appeared in Africa 200,000 years ago, new research suggests.
Scientists conducting one of the most detailed genetic studies of human DNA from populations around the world claim to have been able to pin down when our species spread around the world.
They found the group who left Africa and spread around the rest of the world split from the ancestors of modern African hunter-gatherer populations around 130,000 years ago.
Scientists have conducted a detailed analysis of DNA from 142 populations around the world that has enabled them to piece together how early Homo sapiens migrated around the globe. The map above shows the location of new genetic variants discovered with red being greatest
ABORIGINAL AUSTRALIANS DID NOT EXIT AFRICA EARLY
In the first major genomic study of Aboriginal Australians, researchers have confirmed that along with European and Asian ancestral groups, Papuan and Australian genomes too can be traced back to this migration.
The new evidence supports the idea that there was just ‘one exit event’.
However, once out of Africa, the Papuan and Aboriginal ancestors branched off early on, with some eventually reaching Australia, where they would remain isolated from the rest of the world for thousands of years.
A second study looking at the genomes of indigenous Papua New Guineans found they can trace 2 per cent of their genomes to an earlier but now extinct group of Homo sapiens that left Africa around 120,000 years ago.
This suggests the ancestors of those living in Papua New Guinea may have met and bred with these earlier pioneers before they died out.
However, most populations living outside Africa appear to not have encountered these earlier Homo sapien migrants.
Their study reveals that humans appear to have begun forming isolated groups around that time, fracturing and spreading across the continent and eventually around the world.
Modern non-Africans appear to have last shared an ancestor with members of the KhoeSan hunter-gather peoples found in South Africa around 131,000 years ago.
They last shared a common ancestor with the Mbuti, a group of indigenous pygmy tribes in the Congo of west Africa, around 112,000 years ago.
The researchers, whose work is published in the journal Nature, conclude that there was just a single wave of human migrations out of Africa that led to the modern populations around us today.
Dr Swapan Mallick, bioinformatics systems director in the department of genetics at Harvard Medical School who was first author of the study, said: ‘It had been unclear whether the group that expanded out of Africa represented a large subset of the populations within Africa.
‘This really shows that there was a lot of substructure prior to the expansion.’
Writing in the journal, the researchers added: ‘We infer that the population ancestral to all present day humans began to develop substructure at least 200,000 years ago.’
It comes as another study published alongside it, estimates that the ancestors of all modern humans living outside Africa began migrating out of the continent around 75,000 years ago.
The Harvard study, which was conducted as part of the Simons Genome Diversity Project, analysed 300 genomes from 142 different populations around the world.
The research suggests all modern humans living today emerged from a single population that spread out from African in one migration wave. As they spread around the globe some of these modern populations interbred with other extinct human species (illustrated)
These included 20 populations from ethnic groups in Africa along with many other small populations from around the world, which they could then compare to genomes from larger populations.
Professor David Reich, a geneticist at Harvard Medical School who led the study, said: ‘As humans, we are not just the people who live in industrialised countries, and we are not just the people who live in numerically large groups.
‘If we want to understand who we really are, we have to realise that some of the most interesting aspects of human variation are only present in under-represented, small populations.’
Traditional views of human migrations out of Africa have been based on fossils and suggest Homo sapiens may have left in multiple waves, but the new research suggests it was a single migration wave (illustrated). It has also provided greater clarity on diversity in Africa
WHAT THE FOUR STUDIES TELL US ABOUT HUMAN ANCESTRY
The Simons Genome Diversity Project study
After analysing DNA from 142 populations around the world, the researchers conclude that all modern humans living today can trace their ancestry back to a single group that emerged in Africa 200,000 years ago.
They also found that all non-Africans appear to be descended from a single group that split from the ancestors of African hunter gatherers around 130,000 years ago.
The study also shows how humans appear to have formed isolated groups within Africa with populations on the continent separating from each other.
The KhoeSan in south Africa for example separated from the Yoruba in Nigeria around 87,000 years ago while the Mbuti split from the Yoruba 56,000 years ago.
The Estonian Biocentre Human Genome Diversity Panel study
This examined 483 genomes from 148 populations around the world to examine the expansion of Homo sapiens out of Africa.
They found that indigenous populations in modern Papua New Guinea owe two percent of their genomes to a now extinct group of Homo sapiens.
This suggests there was a distinct wave of human migration out of Africa around 120,000 years ago.
The Aboriginal Australian study
Using genomes from 83 Aboriginal Australians and 25 Papuans from New Guinea, this study examined the genetic origins of these early Pacific populations.
These groups are thought to have descended from some of the first humans to have left Africa and has raised questions about whether their ancestors were from an earlier wave of migration than the rest of Eurasia.
The new study found that the ancestors of modern Aboriginal Australians and Papuans split from Europeans and Asians around 58,000 years ago following a single migration out of Africa.
These two populations themselves later diverged around 37,000 years ago, long before the physical separation of Australia and New Guinea some 10,000 years ago.
The Climate Modelling study
Researchers from the University of Hawaii at Mānoa used one of the first integrated climate-human migration computer models to re-create the spread of Homo sapiens over the past 125,000 years.
The model simulates ice-ages, abrupt climate change and captures the arrival times of Homo sapiens in the Eastern Mediterranean, Arabian Peninsula, Southern China, and Australia in close agreement with paleoclimate reconstructions and fossil and archaeological evidence.
The found that it appears modern humans first left Africa 100,000 years ago in a series of slow-paced migration waves.
They estimate that Homo sapiens first arrived in southern Europe around 80,000-90,000 years ago, far earlier than previously believed.
The results challenge traditional models that suggest there was a single exodus out of Africa around 60,000 years ago.
Together with three other studies published in Nature, the Harvard research aimed to test lingering questions about how many waves of migration out of Africa were made by Homo sapiens.
Fossilised remains have suggested that there were several excursions out of the continent while some genetic studies have suggested indigenous populations in Australia, Papau New Guinea and the Andaman Islands descend from a group that left Africa earlier than other non-Africans.
The new studies, however, suggest this is not the case and in fact all modern humans today appear to descend from a single group that split from African Homo sapiens around 130,000-125,000 years ago.
‘Our best estimate for the proportion of ancestry from an early-exit population is zero,’ said Professor Reich.
‘Taken together, all three studies leave wiggle room for, at most, around two percent.’
The researchers now hope to sequence DNA from other small populations in an attempt to expand the analysis.
They say there are thousands of ethnically distinct populations scattered around the globe, so to be definitive, their genomes will also need to be tested.
The researchers say modern populations of humans descend from a single group that emerged in Africa around 200,000 years ago. They say populations outside Africa show signs of interbreeding with Neanderthals (top) and Denisovans (bottom)
The study also found that genetics alone cannot account for the acceleration in cultural and intellectual development that has occurred in the past 50,000 years in humans (recreation of one of the early humans to migrate into Europe pictured)
Intriguing the researchers also found that genetics alone cannot account for the acceleration of cultural, economic and intellectual progress that has occurred in the past 50,000 years.
They say a range of factors such as environment, lifestyle and genes all came together to drive the progress and development made by the human race.
Professor Reich said: ‘Geneticists often search for examples where genetics are the explanation.
‘Here, paradoxically, genetic data are showing that there will be no clear genetic answers.
‘There does not seem to have been one or a few enabling mutations that suddenly appeared among our ancestors and allowed them to think in profoundly different ways.’
THE COMPLEX EVOLUTION OF MAN
55 million years ago – First primitive primates evolve
15 million years ago – Hominidae (great apes) evolve from the ancestors of the gibbon
8 million years ago – First gorillas evolve. Later, chimp and human lineages diverge
5.5 million years ago – Ardipithecus, early ‘proto-human’ shares traits with chimps and gorillas
4 million years ago – Australopithecines appeared. They had brains no larger than a chimpanzee’s
2.8 million years ago – LD 350-1 appeared and may be the first of the Homo family
2.7 million years ago – Paranthropus, lived in woods and had massive jaws for chewing
2.3 million years ago – Homo habalis first thought to have appeared in Africa
1.85 million years ago – First ‘modern’ hand emerges
1.8 million years ago – Homo ergaster begins to appear in fossil record
1.6 million years ago – Hand axes become the first major technological innovation
800,000 years ago – Early humans control fire and create hearths. Brain size increases rapidly
400,000 years ago – Neanderthals first begin to appear and spread across Europe and Asia
200,000 years ago – Homo sapiens – modern humans – appear in Africa
40,000 years ago – Modern humans reach Europe
Link original: http://www.dailymail.co.uk/sciencetech/article-3801995/The-source-humanity-single-group-appeared-Africa-200-000-years-ago-ancestors-humans-living-today.html