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Monday, 22 June 2015

Ice Ages and the development of (human) life

A few weeks ago, I saw a BBC documentary on (probably) Belgian TV which created a clear link between the various ice ages and the development of human beings. After each ice age a more developed human species arrived on Earth. When talking about this, my son asked me when the new ice age will be arriving. Good question, as it had already slipped my own mind.

There have been at least five major ice ages in the earth's past: the Huronian, Cryogenian, Andean-Saharan, Karoo Ice Age and the Quaternary glaciation. Outside these ages, the Earth seems to have been ice-free even in high latitudes. Rocks from the earliest well established ice age, called the Huronian, formed around 2.4 to 2.1 billion years ago. The next well-documented second ice age, and probably the most severe of the last billion years, occurred from 850 to 630 million years ago (the Cryogenian period). (Wikipedia)

Scientists agree that Earth is some 4.5 billion years (Wikipedia). Earliest life on Earth - simple cells - is estimated to have developed some 3.6 billion years ago. Complex life is estimated at some 2 billion years ago. (Wikipedia). Interestingly, complex life thus started after the first known major ice age. The next major development in life was the move from multicellular life to simple animals which is estimated at 600 million years ago. Interestingly, this development starts after the second - most severe - ice age.

The Andean-Saharan (3rd) ice age occurred from 460 to 420 million years ago while the (4th) Karoo Ice Age occurred from 360 to 260 million years ago in the Karoo region of South Africa. After the third ice ages insects, amphibians and reptiles developed. After the fourth ice age mammals, birds and flowers developed. (Wikipedia 1Wikipedia 2)

The current ice age, the Quaternary glaciation, started about 2.58 million years ago. This period coincides with the earliest of humans which is estimated at some 2.5 million years ago (Wiki). Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000 and 100,000 year time scales called the cooler glacial periods and the warmer interglacial periods. The earth is currently in an interglacial, and the last glacial period ended about 10,000 years ago. (Wiki)

The answer to my son's question (1st paragraph) is disturbing as we are already in a new ice age. Yet we are also in an interglacial - warmer - period, called Holocene. A new glacial period is expected in some 80,000 years. The human impact on our climate ("global warming") may delay this peak with a few thousand years (NYT). In this context, the recent agreement amongst world leaders to curb global warming may even appear silly and possibly even against our human self-interest. 

According to the BBC documentary, there is a clear correlation between (inter)glacial periods and the development of the earliest homo species into our own species (homo sapiens). After each glacial period, a more intellectually advanced human species arrived. Intelligence was required to survive Earth's climate conditions. Now we have houses and heating. Still the impact of a new glacial period on human life may well be beyond our comprehension. 

The search for a habitable planet (e.g., NASA, Star Trek) gets a new meaning and purpose.