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New genetic research suggests that the European population at the end of the last Ice Age was barely large enough to escape extinction - http://horizon-magazine.eu/article/ice-age-europeans-roamed-small-bands-fewer-30-brink-extinction_en.html

Almost as if at one stage European humanity was limited to a few ark-sized family groups ...

Sometimes I think it was just the B Ark.

Quote from: Duncan Head on September 09, 2015, 01:10:49 PM
Sometimes I think it was just the B Ark.

Poor bloody cavemen.

Such population reductions may well be what drives evolution as characteristics of the small groups tha survive become dominant when things get better and the population expands. So if the levels of sunlight are poor then groups with light skin survive better until there are no dark skinned people left and when the weather improves and the group grows exponentially everyone is white,nhas a long nose, thick body hair. Evolution by survival of the fittest does not work when everyone survives.
Roy

And what would cause levels of sunlight to be so poor that only a tiny population survived?

What I am thinking of is that there are many traditions of a world-annihilating catastrophe (or even more than one) which are survived by a very small segment of the population (occasionally no more than one individual of each gender).  Might these conceivably have a factual basis?

Living in Scotland seems to contribute to levels of sunlight being so poor few survive.

There has been some research into this topic already, and one interesting fact was that core drills into the ice sheet have found several ash layers, suggesting volcanic activity as a possible cause of rapid cooling of the temperature and poor light leading to both plant and animal extinctions.

And there was me thinking it was deep fried mars bars

The question is what caused the sudden rash of volcanic activity.  We have seen individual volcanoes affect climate over the British Isles quite dramatically (1782-3 and 1815-16) but the climate quickly switches back as the ash is precipitated out of the atmosphere and the population is only marginally affected.  To get enough ash into the atmosphere to cause long-term disastrous effects to life requires a worldwide outpouring by volcanoes such as seems to have occurred in 1629 BC, leading to the dendrochronological 'year of no growth' in 1628.

Any stimulus that would evoke eruptions from volcanoes worldwide would need to be sufficiently forceful to do quite a lot of collateral damage to human and animal populations.  I think the subsequent ash cloud just made life harder for the survivors rather than itself being the main agent of population depletion.

Ash clouds can remain in the upper atmosphere for years. When Krakatoa exploded the ash thrown up was so dense that it caused spectacular sunrises and sunsets for at least three years around the world. There were reports that the nights were so bright for several years after the event that golfers could still play golf at midnight in Scotland. When the Island of Thera detonated in the Mediterranean all kinds of strange weather events occurred, it may have been the cause of the Biblical floods and also the plagues mentioned that occurred in Egypt (Blood rain etc).

I did see one documentary that described an explosion by Krakatoa or similar during the 5^th century.  It postulated that the resultant years of bad harvests were behind both the migration of tribes from Asia to Europe and the Roman Empire's inability to fend them off. 

Don't know how well supported this scenario is amongst those who know more about the subject than me.   

Quote from: valentinianvictor on September 10, 2015, 02:47:44 PM
Ash clouds can remain in the upper atmosphere for years. When Krakatoa exploded the ash thrown up was so dense that it caused spectacular sunrises and sunsets for at least three years around the world. There were reports that the nights were so bright for several years after the event that golfers could still play golf at midnight in Scotland.

Perfectly true.  My point is that this density of ash - the output from one large-scale eruption - did not kill off more than a barely noticeable fraction of the human population and affected crop harvests in the UK for one year only.  Other effects were indeed spectacular but rapidly ceased to be deleterious.

Quote
When the Island of Thera detonated in the Mediterranean all kinds of strange weather events occurred, it may have been the cause of the Biblical floods and also the plagues mentioned that occurred in Egypt (Blood rain etc).

"Around the time of the radiocarbon-indicated date of the eruption, there is evidence for a significant climatic event in the Northern Hemisphere. The evidence includes failure of crops in China (see below), as well as evidence from tree rings, cited above: bristlecone pines of California; bog oaks of Ireland, England, and Germany; and other trees in Sweden. The tree rings precisely date the event to 1628 BCE." - Wikipedia Minoan Eruption entry.

And it would seem that it was not just Thera ... a continuous period of three to nine days of darkness (Egyptian and Hebrew accounts vary) and a subsequent hemisphere-wide die-off of crops and total inhibition of tree growth for close to a year needs a lot more ash cover than a single volcano can provide - or it requires some other cause, which does not per se exclude massive volcanic activity and may in fact have contributed to it.

However even this did not take the European population down to a scattering of platoon-strength groupings.  For that, we are perforce looking at a much more significant event, one which postponed the development of wargaming for millennia ...

The more interesting recent volcano which had significant climatic effects had its bicentenary this April, Tambora, a far bigger event altogether than the 1883 Krakatoa eruption. See the Tambora 1815 Wikipedia page, plus an interesting report on the event from The Economist which latter has a handy interactive map (click on it to go to the map's separate page) showing all known major eruptions from year 0 to 2000 AD. However, Tambora's effects seem to have been combined with the lingering effects of another, but unidentified, eruption in 1809 (known from ice core studies only). And as both pages show, ash is only one component in all this anyway, and perhaps not all that significant a one for longer-term effects.

Quote from: Duncan Head on September 09, 2015, 01:10:49 PM
Sometimes I think it was just the B Ark.

Ever the optimist, Duncan - only sometimes...

In 1783, Laki on Iceland blew its fissures in what is considered the deadliest single eruption in historical times.  It caused a seven-year famine in Iceland itself and wiped out about half the livestock and between a quarter and a third of the population.  Sulphurous gases killed an estimated 23,000 people in the British Isles in 1783-4.  It is estimated that Laki killed six million people worldwide.  Complicating calculations is the fact that Grímsvötn was also erupting from 1783 to 1785.

We may note that even on Iceland, where the multiple eruption originated and had its deadliest effect, at least two thirds of the population survived and the genetic pool remained basically unaltered.

Quote from: Sharur on September 10, 2015, 11:49:22 PM

And as both pages show, ash is only one component in all this anyway, and perhaps not all that significant a one for longer-term effects.

All of this points to a catastrophe of tremendous proportions - not just one eruption or even a few simultaneous eruptions - being required to create the Ice Age population bottleneck.