Friday, 28 November 2014

Our Chequered Past

I am red-haired, with blue eyes with a pale, freckled skin that burns easily, so it is clear that Tropical Africa is hardly my natural environment. In fact, I am a rather typical common or garden human specimen originating from North West Europe. So why do so many Northern Europeans have blue eyes, fair or red hair and a pale skin? Why are Scandinavians and the Dutch so tall in comparison to other people?


Stinne Andreasen put these questions to Peter K A Jensen of the University of Aarhus in Denmark. Dr Jensen has been involved in the study of the origins of humankind and our development for most of his life The answers to these questions he says are to be found thousands of years ago with all our ancestors. These were the first modern humans  who lived in the Southern part of East Africa many thousands of years ago.


All people on earth today can trace their ancestry and origins back 50-60 000 years ago to this place in Sub-Saharan Africa before spreading ourselves all over the world. Then, each one of us had brown eyes, dark hair and dark skin to protect us from the sun’s ultra violet rays.



So how did pale skin come about? Jensen reckons this began 10-15 000 when the first people from Africa settled in Europe at the end of the Ice Age so even then there was not much sunlight around and precious little in the winter. This was a problem as these first Northern Europeans needed sunlight to make Vitamin-D for their bodies. Over time they developed a lighter skin colour that could more easily absorb Vitamin-D from the sun than in the past.

At the same time reproduction and natural selection meant that partners with a lighter skin were attractive as they were exotic  in comparison to the darker skinned majority. In general it can be said  the closer to the Equator you live the darker your skin will be.

Of course there are exceptions; the Inuit do not need pale skin. They get enough Vitamin D from their diet, from seal, whale and liver, so do not need the vitamins from the sun.

In contrast Australian Aborigines are overwhelmingly light in colour; but that is because many are of mixed-descent, having European ancestors.

There are problems too when it comes to migrations into and out of places as regards skin colour. Australia has the highest incidence of skin cancer because pale skin cannot tolerate strong UV rays from the sun. In contrast immigrants from the South to the North often end up lacking Vitamin-D because their skin works too well at keeping out what little sun is available to the skin.



What about fair and red hair? We do not know as much about this as our skin, but there is a clear relationship between skin type and hair colour. Some of the gene mutations that give rise to very pale skin also give rise to fair and red hair. But it is more complex than just that.



And blue eyes? Again we do not know for certain why blue, grey and green eyes are so common in N Europe. The most rational explanation again is probably natural selection, reproduction and adaptation. Just as pale skin was exotic, so were blue eyes so they had a better chance of reproducing themselves than brown eyes. But the vast majority of humankind have brown eyes.



Northern Europeans’ height has increased in the past 100 years due certainly to improved social and living conditions and better nutrition but N Europeans are on average several centimetres taller than Italians or Spaniards. There has been little change in average heights since 1980s, so Europeans have probably reached their maximum possible heights given our gene pool. There are also climactic and topographic reasons in considering why some peoples are taller than others.


If you live in a hot dry place you need to be able to lose heat quickly to avoid overheating. A tall thin body ensures the body’s surface area is greater in relation to your mass and allows a faster loss of heat. The Masai are some of the world’s tallest people as they are built to survive the dry open savanna in Sudan, Kenya and Tanzania.


If you live in the Arctic you tend to be small and squat. The Inuit and Laplanders have a relatively small body surface area in comparison to their mass so it is easier to keep warm.



Why are Northern Europeans so heavy? Yes, they live in the richest and most developed part of the world. Yes, they eat too much and do not exercise enough. But that is not the whole reason. Our African ancestors weighed between 30-40 kilos.

Several hundred thousand years ago, before modern humans migrated from Africa, another group of people lived in Europe; they were called the Neaderthals. They were even heavier than us today around 25% heavier. They adapted well to the Ice Age climate and conditions but had, nevertheless, a physically hard and challenging every-day life. They were burly and tough with, well-devolped muscles and big bones. Most Northern Europeans have some of their genes too.

So modern Northern Europeans weigh less than Neaderthals but more than their parents or grandparents because we have got fatter. This tendency has grown in the recent past and will probably continue in the years to come.

Jensen ends by pointing out that with globalisation and recent mass migrations throughout the world, it is extremely likely that more Northern Europeans will have darker eyes, hair and skin in the future, but the pale Northern European is unlikely to become extinct as blue eyes, light hair and skin will become exotic and attractive again in the areas of natural selection and human reproduction.

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