The Ice Cages Melt

The World Without Us —Alan Weisman— (Chapter 16: Our Geologic Record)         180 miles northeast of Yellowknife, Northwest Territories, Canada: a very round hole half a mile wide and 1,000 feet deep. A dried-up lake.       North of the 60th parallel, Canada contains more lakes than the rest of the world combined. Nearly half of Northwest Territories isn't land at all, but water.       Ice ages gouged cavities into which ice-bergs dropped when the glaciers retreated. When they melted, these earthen kettles filled with fossil water...       Evaporation is slow in cold climates, little more precipitation falls here than in the Sahara.         But: as the permafrost thaws around these kettles, glacial water held in place by frozen soil for thousands of years is seeping away.         In the Eocene, today's lichen-covered tundra was coniferous forest.         One of the oldest mammal species on Earth still lives here, a Pleistocene relic that managed to survive because it was extraordinarily equipped to brave weather that ice-age humans preferred to escape: the musk ox.         The pelage of the musk ox, known in Inuit as qiviut, is the warmest organic fiber known. It makes them impervious to cold but became their downfall when they were all but exterminated by hunters in the early 20th century who sold their hides in Europe.         If too much of the permafrost is undone, it would thaw deeply buried ice that forms crystalline cages around methane molecules.          An estimated 400 billion tons of frozen methane deposits, known as clathrates, lie a few thousand feet beneath the tundra, and even more are found beneath the world's oceans.         That very-deep-freeze natural gas is estimated to equal all known conventional gas and oil reserves. But it is so dispersed no one has come up with an economical way to mine it.         If it all floats away once the ice cages melt, that much methane might ratchet global warming to levels unknown since the Permian extinction, 250 million years ago.

The Beginnings

Guns, Germs, and Steel: The Fates of Human Societies - Jared M. Diamond– (Chapter 1: Up to the Starting Line)         Human history, as something separate from the history of animals, began in Africa about 7 million years ago (estimates range from 5 to 9 million years ago).       A population of African apes broke up into several populations, of which one proceeded to evolve into several populations, of which one proceeded to evolve into modern gorillas, a second into the two modern chimps, and the third into humans.     The gorilla line apparently split off slightly before the split between the chimp and the human lines.     The evolutionary line leading to us achieved a substantially upright posture by around 4 million years ago, then began to increase in body size and in relative brain size around 2.5 million years ago.               Protohumans are generally known as Australopithecus Africanus, Homo habilis, and Homo erectus, which apparently evolved into each other in that sequence.         Homo erectus, around 1.7 million years ago, was close to us modern humans in body size, but its brain size was still barely half of ours.         Stone tools became common around 2.5 million years ago, but they were merely the crudest of flaked or battered stones.         The first human ancestor to spread beyond Africa was Homo erectus, as is attested by fossils discovered on the Southeast Asian island of Java and conventionally known as Java man.                African and European skulls of half a million years ago were sufficiently similar to skulls of us moderns that they are classified in our species, Homo sapiens, instead of in Homo erectus.          The earliest unquestioned evidence of humans in Europe stems from around half a million years ago, but there are claims of an earlier presence.         11,000 B.C. This date corresponds approximately to the beginnings of village life in a few parts of the world, the first undisputed peopling of the Americas, the start of the Pleistocene Era and last Ice Age.         Plant and animal domestication began in at least one part of the world within a few thousand years of the start of the Recent Era 13,000 years ago.