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Friday, 10 August 2018

The Human Diaspora

Today, our planet has some 8 billion humans. That human explosion started after the end of the last Ice Age, some 20,000 years ago. The Last Glacial Maximum had decimated global human population between 20,000-40,000 years ago. Africa, China and Europe each only had a few thousand people left. Humanity barely survived its population bottleneck. (Nature-2011)

This decimation in human population to only thousands, coincides with the "abrupt genetic changes" from "anatomically modern humans" to "behavioural modern humans", "around 40,000–50,000 years ago". It's also easier to understand religious creation stories (eg, Adam and Eve) in case of a global human population of only thousands.

The last glacial period facilitated human migration as the ocean and sea levels were some 120-140 metres lower. The Southern Dispersal route - or coastal migration hypothesis - makes sense: from Ethiopia to Yemen and from Oman either to Iran or Iraq. There humans met and interbred with the Neanderthal, who escaped the European Ice Age and "expanded into Southwest and Central Asia". This explains the 2.5% Neanderthal DNA in humans outside Africa.

The global deglaciation following the Last Glacial Maximum caused extreme climate change: post-glacial sea levels rose by some 120-140 metres from about 20,000 to 8,000 years ago. Also see my 2016 blog the Great FloodWiki: "Outside these [5 major ice] ages, the Earth seems to have been ice free even in high latitudes".

Post-glacial climate change turned the ancient Green Sahara into the current Sahara or Great Desert between 11,000 and 5,000 years ago (2017 study by University of Arizona). This event coincides with the emergence of the "black-headed" Sumerian people in Iraq city-states, like Ur. The Sumerian people were already skilled sailors (eg, AO, DSHaaretz). 

A 2018 study on mitochondrial DNA clusters shows that nothing much survives a major Ice Age: "The study's most startling result, perhaps, is that nine out of 10 species on Earth today, including humans, came into being 100,000 to 200,000 years ago." (Phys-2018). 

Jesse Ausubel, director of the Program for the Human Environment at The Rockefeller University, gave an interesting comment on this 2018 study: "Viruses, ice ages, successful new competitors, loss of prey—all these may cause periods when the population of an animal drops sharply. In these periods, it is easier for a genetic innovation to sweep the population and contribute to the emergence of a new species."

To some extent, humans have engineered their own survival by delaying a new glacial period several times (eg, Bloomberg-2016, NYT-2003, my 2015 blogmy 2018 blog). It's ironic that so many people complain about the dangers of global warming without realising that this global warming was crucial in human survival.

Ironic (1996) by Alanis Morissette - artist, lyrics, video, Wiki-1, Wiki-2


Note: all markings (bolditalicunderlining) by LO unless stated otherwise