It seems our ancestors were relatively few in number

The New York Times has published an interesting article describing what genomes have taught us about our ancestors. Here’s a short extract.

From the composition of just two human genomes, geneticists have computed the size of the human population 1.2 million years ago from which everyone in the world is descended.

They put the number at 18,500 people, but this refers only to breeding individuals, the “effective” population. The actual population would have been about three times as large, or 55,500.

Comparable estimates for other primates then are 21,000 for chimpanzees and 25,000 for gorillas. In biological terms, it seems, humans were not a very successful species, and the strategy of investing in larger brains than those of their fellow apes had not yet produced any big payoff. Human population numbers did not reach high levels until after the advent of agriculture.

Geneticists have long known that the ancestors of modern humans numbered as few as 10,000 at some time in the last 100,000 years. The critically low number suggested that some catastrophe, like disease or climate change induced by a volcano, had brought humans close to the brink of extinction.

If the new estimate is correct, however, human population size has been small and fairly constant throughout most of the last million years, ruling out the need to look for a catastrophe.

There’s more at the link. Recommended reading.

In related news, it seems that four out of five European men (and thus, of course, most Caucasian men in the USA, who are largely descended from Europeans who settled here) can trace their descent to an influx of farmers from the Near East about ten thousand years ago. The Daily Mail reports:

Most Britons are direct descendants of farmers who left modern day Iraq and Syria 10,000 years ago, a new study has shown.

After studying the DNA of more than 2,000 men, researchers say they have compelling evidence that four out of five white Europeans can trace their roots to the Near East.

The discovery is shedding light on one of the most important periods of human history – the time when our ancient ancestors abandoned hunting and began to domesticate animals.

The invention of farming led to the first towns and paved the way for the dawn of civilisation.

The Leicester University study looked at a common genetic mutation on the Y chromosome, the DNA that is passed down from fathers to sons.

They found that 80 per cent of European men shared the same Y chromosone mutation and after analysing how the mutation was distributed across Europe, were able to retrace how Europe was colonised around 8,000BC.

Prof Mark Jobling, who led the study: ‘This was at the time of the Neolithic revolution when they developed a new style of tools, symmetrical, beautiful tools.

‘At this stage about 10,000 years ago there was evidence of the first settlements, people stopped being nomadic hunter-gatherers and started building communities.

‘This also allowed people to specialise in certain areas of trade and make better tools because there was a surplus of food.’

European farming began around 9,000 BC in the Fertile Crescent – a region extending from the eastern Mediterranean coast to the Persian Gulf and which includes modern day Iraq, Syria, Israel and southeast Turkey.

The region was the cradle of civilisation and home to the Babylonia, Sumer and Assyrian empires.

The development of farming allowed people to settle down for the first time – and to produce more food than they needed, leading to trade and the freedom to develop new skills such as metal working, building and writing.

Some archaeologists have argued that some of these early farmers travelled around the world – settling new lands and bringing farming skills with them.

But others have insisted that the skills were passed on by word of mouth, and not by mass migration.

The new study suggests the farmers routinely upped sticks and moved west when their villages became too crowded, eventually reaching Britain and Ireland.

The waves of migrants brought their new skills with them. Some settled down with local tribes and taught them how to farm, the researchers believe.

‘When the expansion happened these men had a reproductive advantage because they were able to grow more food so they were more attractive to women and had more offspring,’ said Prof Jobling.

Again, there’s more at the link.

It’s fascinating to think that we – the human race, today many billions strong – grew from such small, fragile beginnings. Just think how many accidents or disasters could have wiped out the small community of humans at any time in the past. What would this world be like today if we hadn’t prospered and grown as we have? Would intelligent dinosaurs be researching what wiped out the humans?

Peter