Pleistocene characteristics, subdivisions, flora and fauna

3396
David Holt

The Pleistocene it is the first geological division of the Quaternary period. It was characterized by the low temperatures that covered the planet and by the appearance of large mammals, such as the mammoth. Likewise, this time is an obligatory reference when studying the evolution of the human species, since it was during the Pleistocene when the ancestors of modern man appeared..

The Pleistocene is one of the most studied geological divisions and with the most fossil records, in such a way that the information available is quite extensive and reliable..

Typical Pleistocene landscape. Source: Mauricio Antón [CC BY 2.5 (https://creativecommons.org/licenses/by/2.5)]

Article index

  • 1 General characteristics
    • 1.1 Duration
    • 1.2 Little displacement of the continents
    • 1.3 Predominance of low temperatures
    • 1.4 Much of the planet was covered in ice
    • 1.5 Megafauna
    • 1.6 Human development
  • 2 Geology
    • 2.1 Geological effects of glaciations
    • 2.2 Decrease in sea level
    • 2.3 Bodies of water during the Pleistocene
  • 3 Climate
  • 4 Flora
  • 5 Fauna
    • 5.1 Megafauna
  • 6 Evolution of the human being
  • 7 Divisions
  • 8 References

General characteristics

Duration

The Pleistocene began approximately 2.6 million years ago and ended at the end of the last ice age in approximately 10,000 BC..

Little displacement of the continents

During this time, continental drift was very little and has remained that way ever since. By that time, the continents occupied the positions they currently have, in such a way that the distribution of the Earth did not undergo major modifications..

Low temperatures prevail

The Pleistocene climate was a succession of glacial cycles, which means that there were periods of glaciations, followed by others in which temperatures increased, known as interglacial periods. Thus it remained throughout the Pleistocene, until the end of the last ice age, known as Würn.

Much of the planet was covered in ice

According to information gathered by specialists, approximately 30% of the planet was perennially covered with ice during this time. The areas that remained this way were mainly the poles.

At the South Pole, Antarctica was completely covered in ice, as it is today, and at the North Pole, the lands of the Arctic Circle were also covered..

Megafauna

During the Pleistocene epoch, the great mammals such as the mammoth, the mastodons and the megatherium lived their maximum splendor, which practically dominated the landscapes of the planet. Its main feature was its large size.

Human development

In the Pleistocene the ancestors of modern man (Homo sapiens), such as Homo erectus, Homo habilis and the Homo neanderthalensis.

geology

During the Pleistocene epoch there was not much activity from the geological point of view. Continental drift appears to have slowed down compared to earlier times. According to specialists, the tectonic plates on which the continents sit have not moved more than 100 km from each other.

The continents were practically already in the positions they occupy today. Even areas that today are submerged under the sea were on the surface, forming bridges between continents..

Such is the case of the area that today is known as the Bering Strait. Today it is a water channel that connects the Pacific Ocean with the Arctic Ocean. However, during the Pleistocene it was a strip of land that communicated the westernmost tip of North America with the easternmost tip of Asia..

The Pleistocene was also characterized by the abundance of the phenomenon known as glaciations, through which the planet's temperature decreased notably and a large part of the territories of the continents were covered with ice..

Specialists have verified that during this time Antarctica was completely covered by a polar cap, as is the case today.

Vision of the Earth during an ice age. Source: Ittiz [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Likewise, it is known that the ice layer that formed on certain areas of the continents could reach a thickness of several kilometers, between 3 and 4 km.

Geological effects of glaciations

As a result of the many glaciations that the planet experienced during this time, the surface of the continents was affected by an erosive process. Likewise, the existing bodies of water in the interior of the continents were modified, even emerging new ones with the end of each ice age..

Decrease in sea level

In the Pleistocene, the sea level decreased markedly (approximately 100 meters). The main cause of this was the formation of glaciers.

It is important to mention that during this time, there were a lot of glaciations, so the formation of glaciers was quite common. These glaciers caused this decrease in sea level, which would be reversed during interglacial periods.

As expected, when there was an ice age, the sea level dropped. When this remitted and it was in the presence of an interglacial period, the sea level increased.

This resulted in the formation of structures called by specialists as marine terraces, which have the appearance of steps on the coasts..

The study of these marine terraces has been of great importance within the field of geology, since it has allowed specialists to deduce, among other things, the amount of glaciations that have occurred..

Bodies of water during the Pleistocene

The configuration of planet Earth was very similar to what it has today. In such a way that the oceans and seas were practically the same.

This is how the Pacific Ocean was and continues to be the largest body of water on the planet, occupying the space between the American continent and Asia and Oceania. The Atlantic Ocean was the second largest ocean, located between America and the African and European continents..

Towards the south pole is the Antarctic Ocean and at the north pole the Arctic Ocean. In both the temperatures are very low and are also characterized by the presence of glaciers and icebergs..

The Indian Ocean is located in the space between the east coast of Africa and the Malay Peninsula and Australia. To the south it connects with the Antarctic Ocean.

The bodies of water that did undergo certain modifications during the Pleistocene were those that were found in the interior of the continents, since, thanks to the glaciations and the melting of the ice sheets that covered certain areas of the continents, lakes and rivers could be seriously modified. All this according to the evidence collected by specialists on the subject.

Weather

The Pleistocene was a geological age that, for some specialists, must be known as the Ice Age. For others, this name is erroneous, since in the Pleistocene a series of glaciations followed one another, between which there were periods in which the ambient temperatures rose, known as interglacials..

In this sense, the climate and environmental temperatures were fluctuating throughout the period, although temperatures did not rise as much as in other periods of Earth's geological history..

The climatic conditions observed in the Pleistocene are a continuation of the climate of the previous epoch, the Pliocene, at the end of which the temperatures of the planet dropped considerably.

In this sense, the main characteristic of the Pleistocene climate were the glaciations that occurred, as well as the formation of thick layers of ice on the surface of the continents..

The latter was observed mainly in the strips of land closest to the poles. Antarctica was covered with ice for almost all of the time, while the northern extremes of the American and European continents were covered with ice during the glaciations..

During the Pleistocene there were four glaciations, separated from each other by interglacial periods. Ice ages have a different name on the European continent and on the American continent. These were the following:

  • Günz: known by this name in Europe, in America it is known as the Nebraska glaciation. It was the first glaciation that was recorded in the Pleistocene. It ended 600,000 years ago.
  • Mindel: known in the American continent as the Kansas glaciation. It happened after an interglacial period of 20,000 years. It lasted 190,000 years.
  • Riss: third glaciation of this time. It is known in America as the Illinois glaciation. It had its end 140,000 years ago.
  • Würm: it is known as the Ice Age. In the American continent it is called the Wisconsin glaciation. It began 110,000 years ago and ended approximately 10,000 BC..

At the end of the last ice age, a post-glacial period began that has lasted to the present day. Many scientists believe that the planet is currently in an interglacial period and that it is likely that in a few million years another ice age will unleash.

Flora

Life during this time was quite diverse, despite the climatic limitations that were observed with the glaciations.

During the Pleistocene on the planet there were several types of biomes, restricted to certain areas. In such a way that the plants that developed were those of each biome. It is important to note that many of these plant species have survived to this day..

Towards the northern hemisphere of the planet, within the Arctic Circle, the tundra biome developed, characterized by the fact that the plants that grow in it are small. There are no big, leafy trees. A characteristic type of vegetation of this type of biome are lichens.

Another biome that was observed in the Pleistocene and that still persists is the taiga, whose predominant plant form is coniferous trees, which sometimes reach great heights. According to fossil records, the presence of lichens, mosses and some ferns was also appreciated.. 

Similarly, the temperate meadows biome appeared, in which plants such as grasses were observed.

In the interior of the continents, in places where temperatures were not so low, plant forms such as large trees flourished, which later formed large forests.

It is worth noting the emergence of thermophilic plants. These are nothing more than plants that have the necessary adaptations to withstand extreme levels of temperature. As expected, the temperatures to which they had to adapt was cold, well below zero..

In this same vein, during this time deciduous trees also emerged, which lost their leaves in certain periods of time, especially during the coldest times..

It is important to note that with each glaciation that occurred, the landscape changed a little and during the interglacial periods, new plant forms emerged..

Fauna

During the Pleistocene, mammals continued to be the dominant group, thus maintaining the hegemony begun in earlier times. One of the highlights of the fauna in the Pleistocene was the emergence of the so-called megafauna. These were nothing more than large animals, which were also capable of withstanding the low temperatures prevailing at this time..

Likewise, other groups that continued their diversification during this time were birds, amphibians and reptiles, many of which have remained until today. However, as described above, mammals were the kings of this era..

Megafauna

It was made up of large animals. Among the best known representatives of this group we can mention the mammoth, the megatherium, the smilodon and the elasmotherium, among others..

Mammut

They belonged to the genus Mammuthus. In appearance they were very similar to the elephants that exist today. As it belongs to the order Proboscidea, its most representative characteristic was the great nasal prolongation, which is colloquially called the proboscis, whose proper name is proboscis. Likewise, mammoths had long sharp fangs that had a characteristic curvature that oriented them upwards..

Depending on whether they were near or far from areas with lower temperatures, their body was covered with thick fur. Their eating habits were herbivorous.

The mammoths became extinct in the following epoch, the Holocene. However, the abundant fossil records have allowed us to know a lot about this species.

Megatherium

Belonging to the order Pilosa, the Megatherium was related to the current sloths.

It was one of the largest animals that populated the earth. They had an average weight of 2.5 - 3 tons and were approximately 6 meters long. The collected fossils allow us to affirm that their bones were quite robust.

Like modern sloths, they had very long claws, with which they could dig for food. They were herbivores and are believed to have solitary habits.

Example of the megafauna. Source: DiBgd [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]

His body was covered by thick fur that protected him from the intense cold. He lived in South America.

Smilodon

They belonged to the Felidae family, so it is considered that they were relatives of the current felines. Its most prominent feature, apart from its large size, were the two long fangs that descended from its upper jaw. Thanks to these, the smilodon has been known worldwide as "saber-toothed tiger".

According to the collected fossils, it is believed that the males of this species could reach up to 300Kg in weight. Regarding their habitat, they lived mainly in North and South America. The site where the largest amount of smilodon fossils has been recovered is at Rancho La Brea in California, United States.

Elasmotherium

It was a large mammal, belonging to the Rhinocerotidae family, related to today's rhinos. Its characteristic element was a large horn that protruded from its skull and that at times could measure up to more than 2 meters.

It was herbivorous and fed mainly on grass. Like the other mammals of the time, its enormous body was covered by thick fur. It inhabited the area of ​​Central Asia and the Russian steppes.

Human evolution

During the Pleistocene the human species began to develop into modern man. The direct ancestors of the human being were the Homo habilis, Homo erectus Y Homo neanderthalensis.

The Homo habilis was characterized by beginning to manufacture and use simple tools, probably made of stone and metal. Likewise, he built cabins and formed settlements. His habits were sedentary.

Later the Homo erectus. This had a wider distribution than that of the Homo habilis. Fossils have been found not only in Africa, but also in Europe, Oceania, and Asia. They were the first to develop some sense of social coexistence. They established groups to live in society.

The Homo neanderthalensis they had a brain slightly larger than that of today's human being. His body developed certain adaptations to the cold. However, he resorted to his ingenuity to protect himself, making suits with animal skins. According to what is known, the Homo neanderthalensis presented some social organization, as well as rudimentary verbal communication.

Finally modern man made his appearance, the Homo sapiens. Its main characteristic is the extensive development that its brain reached. This has allowed him to develop activities such as painting and sculpture. Likewise, he established a society in which there is a marked social hierarchy.

Divisions

The Pleistocene is divided into four ages:

  • Gelasian: started 2.5 million years ago and ended 1.8 million years ago.
  • Calabrian: started 1.8 million years ago to 0.7 million years ago.
  • Ionian: starting 0.7 million years ago to 0.12 million years.
  • Tarantian: It began 0.12 years ago and lasted until 10,000 BC..

References

  1. James, N. and Bone Y. (2010). The Pleistocene record. Neritic carbonate sediments in a temperate realm: Southern Australia.
  2. Lewin, R. (1989). Human evolution Editorial Salvat.
  3. Turbón, D. (2006). Human evolution. Editorial Ariel.
  4. Wall, J.D. and Przeworski, M. (2000) "When did the human population start increasing?" Genetics 155: pp. 1865-1874
  5. Wicander, R. and Monroe, J. (2000). Fundamentals of Geology. 2nd edition.
  6. Zafra, D. (2017). The Quaternary period, ice ages and humans. Industrial University of Santander.

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