Out of Africa - The journey

In the book, ‘The Scots - A genetic Journey’,  ISBN: 978 1 84158 941 1

Alistair Moffat and James Wilson write:- And I summarise:

Modern man started to move from the central rift valley in Africa about 70,000 years ago. For some time it was unclear what caused this to happen. Climate change was suspected. Recent archeological and geological evidence has recently emerged shedding new light on these events.

A little over 70.000 years ago Lake Toba filling the vast crater of a Super-Volcano twenty miles in diameter erupted. Mount Toba was located in the area of what is now Samartra. This appears to be the largest volcanic eruption recorded since modern man emerged about 150,000 years ago. The effect was devastating plunging the entire world into a six to ten year volcanic winter. As the skies darkened by the ash cloud, Little or no sunlight could penetrate, therefore plants withered and died. A blanket of ash fifteen centimeters thick covered the Indian sub-continent.

With little or nothing to eat animals died in their millions and the population of people, of Homo sapiens, appear to have teetered on the brink of extinction.

Scientist believe that the Toga left only a tiny group, perhaps just five or ten thousand people alive, and it seems that they survived in a refuge in the rift valleys of central Africa. Of these only a few were able to conceive and give birth and we are all of us descendants of this tenacious remnant....

Understanding the structure of DNA or DeoxyriboNucleicAcid quickly led to a clear sense of how it worked. DNA is one of the central building blocks of life and the key to individual identity. Studies from DNA populations around the world have revealed how similar all humans are compared to, say, fruit flies or chimpanzees. This is because humans are a very young species and there has been less time for changes to occur. People like us first came on the archaeological record in Africa about 150,000 years ago, a mere moment in evolutionary time. Other species are millions of years old.

It is important to understand that African DNA is special, it is more diverse than non-African DNA. The reason, humans have lived in Africa for far longer.

When the early communities of Homo sapiens in Africa were decimated some time around BC 70,000 by the super-eruption of the volcano Toba, a tiny number of only a few hundred survivors detached themselves from the main remnant groups and began to move north from the rift valleys. Thus began an immense journey that would ultimately populate the whole of the rest of the world.

When these groups reached the horn of Africa, they crossed to the Indian Ocean coast of the Arabian Peninsula. ‘The Gate of Tears’ as it is known that leads into the Red sea is only ten miles wide between modern Djibouti and the Yemen but, even over that distance, boats will have been needed to reach the far shore.

As the pioneers reached the Persian Gulf, some appear to have swung northwards to the lands watered by the river Tigris and Euphrates. This region, once known as Mesopotamia was the place from where modern human beings, Homo sapiens, eventually began to move into Europe and mid-Asia. These

lands were not devoid of inhabitance, for hundreds of thousands of years Neanderthals had lived and managed to survive both large and small Ice ages and Toba.

Many wondered if Neanderthals and Homo sapiens mixed, certainly Neanderthals eventually went extinct as a race of humanoids. Exiting recent research has revealed startling new information about human DNA. When the bands of Homo sapiens from Africa reached Mesopotamia and the Levant (Israel) around 60.000 BC, they encountered groups of Neanderthals - and on occasions mated with them.

Scientists at the Max Planck Institute in Leipzig have now sequenced the whole Neanderthal genome from the powdered bone fragments of three females who lived in Europe around 40,000 BC. They then compared their DNA with the genomes of five people from France, China, Western Africa, southern Africa and Papua New Guinea. There was no correlation with the two sets of African DNA but, sensationally, it became clear that between 1% and 4% of the DNA of the non-African lineages comes from the Neanderthals.

In August 2012 it was reported that genetic scientist working in the United States had found evidence that showed that modern man, moving out of Africa interbred with Neanderthal females produced offspring with stronger immune systems. Writing in the US journal ‘Science” they say that some of the genes that modern humans fight illness with, were inherited through cross breeding with Neanderthals. They said that many people have a little bit of Neanderthal in them. According to previous analysis up to 4% of the genetic inheritance of modern European and Asian people comes from interbreeding between our distant ancestors and their short muscular cousins. This research suggest that this mating was not just a casual affair. In fact, it was a meaningful relationship, at least for our immune system.

Lead researcher Professor Peter Parham, from Stanford University, California. said cross-breeding contributed to our gene pool. 'The cross-breeding wasn't just a random event that happened, it gave something useful to the gene pool of the modern human,'

Neanderthals, who lived in western Asia and Europe, co-existed with early modern humans for several thousand years before dying out around 30,000 years ago. Homo sapiens, Neanderthals and Denisovans split into different populations from a common African ancestor around 400,000 years ago.

The research, published today in the journal ‘Science’, focused on immune system elements called HLA  genes that are critical to the body's ability to identify and destroy harmful foreign invaders and are among the most variable and adaptable of human genes.

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These scientist say that some genes involved in recognising an attacking dangerous infection came from Neanderthals. We also inherited some immune protection from breeding with another ancient human relation living in eastern Asia - the Denisovans. Whilst the genes we received help us stay ahead of viruses to this day neither the Neanderthals nor Denisovans got much from the exchange, as they disappeared completely some 30,000 years ago.

These analyses give no information on whether or not Neanderthals living in Europe 20,000 years later interbred with our European ancestors and so far there is no evidence of this. These new findings do mean that most Scots and Britons will have inherited a small but variable proportion of their genes from these ancestral Neanderthals of the Near East. It is suggested 4% from Neanderthals and 6% from Denisovans. (the DNA of Papua New Guineans derive 95% of their HLA gene from Neanderthals and Denisovans).

DNA can trace the footprints of our dispersal out of Africa. Although movement east and south-east was rapid, it appears that perhaps 20,000 years passed before bands began to move north towards Europe. Perhaps the way to the west and north was blocked by desert or colder climatic conditions.

However, this site is devoted to PENDRED past not genetics. If you are interested in this fascinating subject I suggest reading Alistair Moffat and James Wilson book, The Scots - A Genetic Journey,  ISBN: 978 1 84158 941 1. Do not be misled by the title, most of the book is devoted to our common British journey to these islands.

The re-population on Britain.

At the end of the last ice age, (circa 9000BC) what are now the British Isles were joined to the European mainland as a mass of land extending north west from the modern-day northern coastline of France, Belgium and the Netherlands. Ice covered almost all of what is now Ireland and Great Britain with the exception of most of modern-day Munster and much of what we now call England.

Between 14,000 to 10,000 years ago, the last major Ice age drew to a close and as the ice melted, sea levels rose separating Ireland from the mainland, creating also the Isle of Man. Between 2000 and 4000 years later, Great Britain became separated from continental Europe. Britain was repopulated with people before the ice age ended and certainly before it became separated from the mainland. It is likely that Ireland became settled by sea after it had already become an island.

The first Farmers to arrive in Britain

Ian Sample, science correspondent guardian.co.uk, Tuesday 19 January 2010 wrote:-

Most British men are descended from ancient farmers. The first farmers to arrive in Britain outbred the native hunter-gatherer men and have left their mark in modern males' Y chromosome, farming in the blood: More than 60%

of British men have the Y chromosome that dates back to the origin of agriculture.

Most ethnically British men in Britain are descended from the first farmers that migrated across Europe from the Near East 10,000 years ago, scientists say.

Ancient farmers left their genetic mark on modern males by breeding more successfully than indigenous hunter-gatherer men as they made their way west, a study has found.

As a result, more than 60% of ethnically British men, and nearly all of those ethnically Irish in Ireland, can trace their Y chromosome back to the agricultural revolution, or more precisely the sexual success of the men behind it. These farmers' Y chromosome becomes more common in the West of England and reaches a national peak of 78% in Cornwall.

Men with surnames including Titchmarsh and Haythornthwaite are among the most likely to carry the farmers' Y chromosome, known as R1b1b2. The Y chromosome is passed down the male line only, from father to son.

"These farmers expanded into territories with small and sparse hunter-gather populations and moved on as time passed. The Y chromosome got caught up in that and it surfed the wave of expansion," said Mark Jobling, a geneticist at Leicester University and an author of the study.

The rise of farming is one of the most important cultural transformations in the history of modern humans. Increased food production allowed communities to settle rather than wander in search for food, a shift that heralded the huge expansion of the human population.

The first European farmers came from the "fertile crescent" that stretched from the eastern Mediterranean to the Persian Gulf, but experts have argued whether the westerly spread of agriculture was driven by the cultural transmission of ideas and technology, or by migrating farmers.

Researchers led by Jobling collected DNA samples from more than 2,500 men across Europe. Around 80% of the men had the R1b1b2 type of Y chromosome, making it the most common lineage on the continent.

A map showing the distribution of the chromosome across Britain reveals that it became increasingly common but less genetically diverse from the south east to the north west. The analysis, published in the journal PLoS Biology, suggests the R1b1b2 Y chromosome entered the country with the earliest farmers in the south east and gradually spread west as they migrated.

Genetic tests on women showed that most are descendants of hunter-gatherer females. "To us, this suggests a reproductive advantage for farming males over indigenous hunter-gatherer males during the switch from hunting and gathering to farming," said Patricia Balaresque, a co-author of the study.

"Maybe back then, it was just sexier to be a farmer."

The book, The Improbable Primate - How water shaped human evolution by Clive Finlayson, throws further light on the waterside ape theory elegantly presented by Sir David Attenborough in his two part radio program aired on BBC radio four in September 2016 who considered whether new evidence will help a once widely ridiculed theory of human origins move towards to mainstream acceptance.

In 1960, the eminent Oxford marine biologist Sir Alister Hardy proposed a revolutionary idea - our human ancestors had started their existence not on the wide savannahs of Africa, but had become accustomed to living alongside water, swimming and diving in the shallows, collecting the abundant food and learning to use language and fashion tools. Hardy asserted that this adaptation to living at the waterside would also account for a whole range of peculiarities about the human form, including the layers of fat beneath the skin, the relative lack of body-hair, the development of language and speech, and what has been called our 'runaway brains'.

Perhaps surprisingly, it was a screenwriter rather than a scientist, Elaine Morgan, who took up Hardy's theory and, for over 40 years, progressively refined the evidence for the idea. Most mainstream paleo-anthropologists ridiculed and rejected the Hardy-Morgan thesis for decades, but some influential scientists asked for the proposal to be approached with an open mind.

Sir David Attenborough first considered the controversial theory on Radio 4 in 2004. In this new series of two programmes, The Waterside Ape, he brings us up to date with the story and the evidence put forward since then - both for the hypothesis and also for its continuing detractors.

Back in 2004, Sir David asked Elaine Morgan how long it would take for the aquatic adaptation theory to become a mainstream account of human origins. She answered, "I'll give it ten years." As we review the new evidence, has she been

Further reading:

The Making of the British Landscape - From the Ice Age to the Present.

by Nicholas Crane.

The Improbable Primate - How water shaped human evolution by Clive Finlayson.

The Humans who went Extinct - Why Neanderthals died out and we survived by Clive Finlayson.