with a 100,000 year time line...
There have been many ice ages. Ice, in fact, is far more common on planet Earth than warming. We are, in fact, lucky when we are living while the planet is warm. There has never been a time (known) when Earth was too hot to support human life, except during its formation. But there have been many times when the Earth was too cold to support human life. If there ever appears a method by which humans can influence the temperature of the earth - and this author believes that method will never appear - then we should take actions to warm the planet, rather than to cool it, for once it begins to cool, it always goes all the way to ice age.

"Ice Age" is technically a very long period of oscillating glaciation, and using that definition, we are still IN the most recent ice age, (no quote marks) which began 2 million years ago. But "ice age" in common parlance means a period of time when snow and ice occupy a large portion of the surface of the earth - land and sea - accompanied by low air temperatures. That particular situation we originate at about 100,000 BC as an easy date to remember, and even so because "ice ages" also tend to last 100,000 years. We set the date of 20,000 BC as the maximum extent of glaciation, and we give its "end" at between 10,000 to 9,000 BC. I will extend the "end" to 5,000 BC, and you will learn, soon, why that is convenient.

The peak glaciation of this Ice Age covered the Northern hemisphere to the level of New England and the US to the level of states bordering the Great Lakes (like Michigan and Wisconsin), and as far South as Switzerland in Europe, so about one-third the planet at peak. Those human populations which had migrated South began returning soon after that peak. When glaciers melt and withdraw, more water forms from melting ice, and sea levels rise. By 5,000 BC the sea is high enough to cover the only remaining land bridge from The British Isles to Europe, and the English Channel is complete. I wanted you to remember when the English Channel formed, and by stretching the "end" of the Last Ice Age to the point where there is enough melting ice to fill it, supplies a marker for both.

Why do that? To improve memory. Click to read "How To Remember Historical Events".

During the second half of the period from 100,000 BC to 5,000 BC, other interesting things were happening. At 40,000 BC, Cro-Magnon Man (an early form of Homo Sapiens) appears in Europe, moving North from the Near East, and by 30,000 Neanderthal has died out, likely as a result. Also at this time, there is sufficient land bridge across the Bering Straits for walkers from Asia to become the first humans to enter the Western Hemisphere. They kept walking, right on down to the tip of South America (by 10,000 BC), leaving what we label Eskimos at the Northern extreme and a variety of Indian sub-groups strung-out along the rest of the way.

The ice age glaciation also moved North from Antarctica into Australia, but soon after 20,000 BC it was possible for humans to survive there. At about 15,000 BC the bow and arrow appears, the first long-range weapon. At 10,000 BC we note the extinction of woolly mammoths, mastodons, saber-tooth cats, and others in the Western Hemisphere, very likely related to the move of the expanding human population from one end to the other.

At 8,000 BC, in the Middle East, agriculture appears, focused around rivers, and once the fertile ground is sufficiently reliable, communities form which stay put. Domesticated animals follow. At 7,000 BC, the walled settlement of Jericho appears, pottery is first fashioned, and (along with it, as there is a high heat source) the appearance of metal working, at first in the form of copper. (Read: "The Stone Age, Bronze Age, Iron Age")

At 5,000 BC, a settlement will appear at Sumer within fertile river valleys, and these people will create the first writing and record the first history, (Read: "History Begins at Sumer.") while not far away, the Nile will achieve its present course, and a unique civilization will appear along its banks, flowing North to the Mediterranean.

And in 5,000 BC, the English Channel will form.

Areas may exist within a large glaciation without being covered by snow and ice because they are too dry to allow snow to form ice. Alaska is an example of that, remaining clear while all of Canada was covered by ice at 20,000 BC. A positive to that is that life may survive in such arid regions to repopulate the whole region. For instance, caves in Alaska show remains of black bears, brown bears, caribou, marmots, and brown lemmings, among others, corresponding to maximum glaciation covering Canada, and all of them had to be eating something.

The history of "ice ages" is a technically long and complicated business, and I have left 99.9% of that out. This is a short essay to cover the high points, provide an easy-to-remember time line, and hopefully act as a teaser to your learning more about ice ages and climate change, particularly the fact that it has made wide swings for millions of years before man even made an appearance. Humans have zero influence on climate change.

The Simplified Time Line:

100,000 BC circaLast Ice Age Begins
  20,000 BC circaMaximum Glaciation
  10,000 BCIce Age retreats to near present state; humans reach tip of So. America.
    5,000 BCEnglish Channel forms as seas rise high enough to do it. Sumer appears.

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