Tuesday, July 03, 2007

Global warming shapes society. Part 1 - Migration

One of the major effects of global warming is adjusted species-range. Plants and animals evolve to survive in a particular climate, and when it changes quickly species follow their preferred climate travelling up the latitudes towards their closest pole, as the planet heats up. They change their range. While many species tend to travel north or south, the only way is up for the American pika - their 1200 years migration from the great American plains has now found them high up in alpine terrain.

Which brings us to us. We are a species too, and we have our range, which is currently every continent bar Antarctica. Yet in the nascence of our evolution as Homo sapiens sapiens, around 150,000 years ago, our range was restricted to the Rift Valley in central Africa - for 50,000 happy years. What happened to make us leave the comfy ancestral home?

Climate change is what happened. :::[Vanity Fair: Out of Africa]

What set these migrations in motion? Climate change—today's big threat—seems to have had a long history of tormenting our species. Around 70,000 years ago it was getting very nippy in the northern part of the globe, with ice sheets bearing down on Seattle and New York; this was the last Ice Age. At that time, though, our species, Homo sapiens, was still limited to Africa; we were very much homebodies. But the encroaching Ice Age, perhaps coupled with the eruption of a super-volcano named Toba, in Sumatra, dried out the tropics and nearly decimated the early human population.


And then something happened. It began slowly, with only a few hints of the explosion to come: The first stirrings were art—tangible evidence of advanced, abstract thought—and a significant improvement in the types of tools humans made. Then, around 50,000 years ago, all hell broke loose. The human population began to expand, first in Africa, then leaving the homeland to spread into Eurasia. Within a couple of thousand years we had reached Australia, walking along the coast of South Asia. A slightly later wave of expansion into the Middle East, around 45,000 years ago, was aided by a brief damp period in the Sahara. Within 15,000 years of the exodus from Africa our species had entered Europe, defeating the Neanderthals in the process.

From the beginning climate change has had an all pervasive influence on our global migrations. And indeed, even on the music of U2. :::[Vanity Fair: Mommy, where Do Bonos Come From?]

The maternal ancestors of Africa-issue guest editor Bono were, like Graydon's, part of the second major migratory wave out of Africa. They moved northward out of the Near East, entering Europe around 30,000 to 40,000 years ago. During the worst of the last ice age, about 15,000 years ago, these ancestors were pushed into Iberia. After the ice age, Bono's ancestors moved northward and westward to populate the British Isles and Scandinavia.

(I always thought I could hear the atavistic strains of the windblown Iberian tundra of 15,000 BCE in New Year's Day).

Our history is one of being shaped by climate change, it's quite ironic that we now shape the climate ourselves. I wondered how it would all turn out:

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1 comment:

alvinwriter said...

These migration maps are very interesting. They really do show how people moved from place to place in response to the changing climate. Perhaps the one with the most effect on the distribution of modern humans today was what happened in the last ice age. Then, lower sea levels allowed people to cross bodies of water particularly in Southeast Asia, which was used as a bridge between Australia and Indochina. It's notable that scientists are now conducting a study on changes, particularly the upwelling of water of the Southern Ocean near Antarctica to see it's role in climate change. I wonder how this will affect the Southern Hemisphere? http://www.thenewsroom.com/details/510007/Science+and+Technology?c_id=wom-bc-ar

It's good to see you have TheNewsRoom here already. It certainly has lots to offer individuals and groups who promote awareness on global warming. If you have inquiries, they'll be happy to help you. Just send to jtowns@voxant.com.

- Alvin from The ScienceDesk at TheNewsRoom.com