The Pleistocene Epoch

Science, IT, Nature

In the next installment (Part 4) of Shanti’s new series, Humans Are Still Young, we meet the first homo sapiens

Pleistocene glacial lake varves
Pleistocene glacial lake varves at Sandend Bay, Scotland. Wikimedia Commons.

After the The Cenozoic Era comes the Pleistocene Epoch, from 1,800,000 to 12,000 years ago. Pleistocene biota are extremely close to modern ones. Many genera and even species of Pleistocene conifers, mosses, flowering plants, insects, mollusks, birds, mammals and others, survive to this day. Yet the Pleistocene is also characterized by the presence of distinctive large land mammals and birds. Mammoths and their cousins, the mastodons, long-horned bisons, sabertoothed cats, giant ground sloths and many other large mammals characterize Pleistocene habitats in North America, Asia and Europe.

The last part of the Pleistocene sees the evolution and expansion of our own species, Homo sapiens.

The genus ‘Homo’ is the youngest twig from a 2.5 million year old branch from a 4.6 billion year old tree, a seedling in a 13.8 billion year old universe. You and I are a recent leaf, or maybe even a flower on that twig!

Anatomically modern humans appear in Africa sometime prior to 200,000 years ago, but I would not have felt at ease with them!

By the close of the Pleistocene, these modern humans are spread through most of the world. They inhabit Eurasia and Oceania by 40,000 years BP (Before Present) and the Americas at least 14,500 years BP.

Around 50,000 BP they have developed full behavioral modernity, including language, music and other cultural universals. I wondered when I started writing this series if they were also the first ones to develop qualities like love and awareness. Would I have felt comfortable with them, not just a prey, in the valley of the Vézère river in the Dordogne in France, lovingly called, by my friend Antoine, ‘La vallée de l’homme’?

Their skull has grown big… but what about their heart?

It is during the Pleistocene that the most recent episodes of global cooling or ‘ice ages’ take place. The present Pleistocene Ice Age is the last of five Ice Ages during the Earth’s history. An age is called an Ice Age when at least one permanent large ice sheet,i.e. Antarctica, exists continuously.

No completely satisfactory theory has been proposed to account for Earth’s history of glaciation. The cause of glaciation may be related to several, simultaneously occurring factors, such as astronomical cycles, called Milankovitch cycles, atmospheric composition, plate tectonics and ocean currents. The combined effect of the three orbital cycles of the Earth around the Sun causes long-term changes in the amount of sunlight hitting the earth at different seasons, particularly at high latitudes.

During an Ice Age, many of the world’s temperate zones are alternately covered by glaciers during cool or glacial periods, and uncovered during the warmer or interglacial periods, when the glaciers retreat. During interglacial times, such as at present, drowned coastlines are common. At one point during the Pleistocene Ice Age, sheets of ice covered all of Antarctica, large parts of Europe, North America, South America and small areas in Asia. It is estimated that, at the maximum glacial extent, 30% of the Earth‘s surface was covered by ice.

While Homo sapiens evolved, many vertebrates, especially large mammals, succumbed to the harsh climate conditions of this period.

Humans lived as hunter-gatherers. Until about 12,000 B.P. you could count about 1 million people worldwide. They exploited whatever flora and fauna were native and available in the various regions they inhabited and colonized. Around that time, and in tune with a warming climate in this interglacial period, the Holocene epoch, humans gradually changed from mobile or semi-sedentary foragers into farmers.

But their situation wasn’t the same everywhere! In his wonderful book, Guns, Germs and Steel: The Fates of Human Societies, Jared Diamond argues that the gaps in power and technology between human societies today originated in environmental differences.

Authors are regularly asked by journalists to summarize a long book in one sentence. For this book there is such a sentence: ‘History followed different courses for different people because of differences among peoples’ environments, not because of biological differences among people themselves.’

Although agriculture arose in several parts of the world, Eurasia gained an early advantage due to the greater availability of suitable plant and animal species for domestication. Eurasia’s large landmass and wide east–west width increased these advantages. Its large area provided more plant and animal species suitable for domestication. Equally important, its east–west orientation has allowed groups of people to wander and empires to conquer from one end of the continent to the other while staying at the same latitude. This was important because similar climate and cycle of seasons let them keep the same ‘food production system – they could keep growing the same crops and raising the same animals all the way from Scotland to Siberia. Doing this throughout history they spread innovations, languages and diseases everywhere.

The plentiful supply of food and the dense populations that it supported made division of labor possible. The rise of non-farming specialists, such as craftsmen and scribes, accelerated economic growth and technological progress. These economic and technological advantages eventually enabled Europeans to conquer the peoples of the other continents in recent centuries by using guns and steel, particularly after the devastation of native populations by the epidemic diseases from germs.

The advent of agriculture prompted trade and cooperation and led to much more complex societies. Because of the significance of this date for human society, the next epoch is called the Holocene or the Human Era.

To be continued…

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Shanti is the creator and compiler of this series, including At Home in the Universe and 1001 Tales.

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