The Quaternary is the last period of the Cenozoic It started 2.59 million years ago and understands to this day.
Until recently the Quaternary did not include age or floor Gelasiano, which began 2,588 million years ago, ends 1,806, and was framed in the last part of the Pliocene. The adjustment was made for consistency with the main changes in life, climate and the Earth's oceans, since the episodes of Gelasian glaciation fit better in this period.
The Quaternary, the age of ice and man
The Quaternary is divided into two epochs: Pleistocene, the first and longest of the period, which includes the glacial centuries, and the Holocene, the recent or postglacial era that reaches today.
The Pleistocene is sometimes called "the era of Man", because the genus Homo evolved in this period. In the next period, the Holocene, human beings were able to develop an organized life in social groups that we call civilization.
•" He Pleistocene It starts 2,588 million years ago and ends about 12,000 years ago, in 10,000 BC. C. The ice spread in the form of glaciers over more than a quarter of the earth's surface, reaching in some areas up to the 40th parallel. The level of the seas dropped about 100 meters and life had to adapt to new conditions or disappear. In the ice-free regions, the dominant flora and fauna were essentially the same as those of the previous period, the Pliocene.
A glacier system was centered over Scandinavia, extending south and east through northern Germany and western Russia, and southwest on the British Isles. The second great glacier system of the northern hemisphere covered most of Siberia. Another glacier system covered Canada and extended to the United States.
Naturally, the Arctic and Antarctic regions were also covered with ice, as were most of the high mountains around the planet. The topographic effects caused by the action of glaciers during the Pleistocene are still noticeable in much of the world.
Six large glaciations occurred throughout the Pleistocene. Among them there were as many interglacial periods in which the weather became warmer. Now we are in the last interglacial period. For now.
In the cold areas lived mammoths, reindeer, giant deer and polar bears. The vegetation was similar to the tundra, with lichen and moss. In the interglacial stages there were horses, rhinos and felines with large fangs. A part of the fauna adapted to climatic changes, such as bison, foxes, elk and wildcats. In North America many species of mammals became extinct, including the llama, the camel, the tapir, the yak and the horse. Towards the end of the Pleistocene, some large mammals, such as the mastodon, the saber-toothed tiger, the giant deer and the lazy terrestrial, had become extinct throughout the planet.
While ice and snow accumulated in the high latitudes, in the lower rains increased, allowing plant and animal life to flourish in areas of northern and eastern Africa that today are barren and arid. Evidence has been discovered that the Sahara was occupied by nomadic hunters, as well as by giraffes and other ruminants during the late Pleistocene.
As for human evolution, the Pleistocene is equivalent to Paleolithic. At first the species Homo habilis, harvester and scavenger appeared, who manufactured rough stone tools. Homo erectus, with greater brain, appeared 2 million years ago. He made more sophisticated weapons, hunted in groups, talked and probably learned to use fire.
Homo neanderthalensis was a species adapted to the cold that appeared 230,000 years ago. Some authors consider it a subspecies or adaptation of Homo sapiens, whose oldest remains are about 315,000 years old and is the only species of Homo that has not yet become extinct.
•" He Holocene it is the most recent period of the Quaternary period and, therefore, of the Cenozoic Era, so recent that it lasts until today. It began about 12,000 years ago, in 10,000 BC. C, when the thaw caused the sea level to rise more than thirty meters. This caused Britain, Indonesia, Japan, Taiwan, New Guinea and Tasmania to separate from their respective continents. The Bering Strait, which separates Siberia from Alaska, formed and the area of the current Sahara desert began to dry slowly, which had hitherto had mild climate, rains and vegetation.
The Holocene in an interglacial period that can end in a new glaciation. It is a time of warm weather in which the current geographical distributions of fauna and flora are based. Variations and cycles occur in which the global temperature rises or falls below 1 ° C.
Extinctions have continued during the Holocene and have accelerated in the last 100 years by human presence. On Earth there were five major extinctions, so the current one is called the sixth extinction.
At the beginning of the Holocene, humans had already begun to organize into social groups located in caves or huts, which made language and, with it, knowledge evolve rapidly. Wolves were tamed to turn them into dogs and new tools were made such as bows, arrows, axes, knives, harpoons, fishing tackle or canoes.
About 10,000 years ago, the inhabitants of the fertile Middle East began to combine hunting and fishing with agriculture and livestock, which led to the abandonment of nomadic life. They settled in stable places forming towns or cities (civitas, in Latin) and from there comes the word "civilization". They made ceramic objects and began to dominate metals: first copper, then bronze and finally iron.
Although, as a geological period, it covers to this day, the Holocene is usually studied until the Invention of writing. The first writing known is attributed to the Sumerians of Mesopotamia, some 5,000 years ago. From this moment begins what we call "history"But that is another history.
• Human evolution
• Quaternary glaciations
• The great river that was forgotten under the Sahara
|The Neogen: Miocene and Pliocene|