The Pliocene was the last epoch of the Neogene period of the Cenozoic Era . It began approximately 5.5 million years ago and ended 2.6 million years ago. It was an important time from the point of view of anthropology, since the first discovered fossils of Australopithecus , the first hominid to inhabit the African continent, date from this time .
This was a time of significant changes in terms of biodiversity, both botanical and zoological, as plants and animals began to be located in the various regions, limited by climatic conditions. This location, in many cases, has been maintained to this day.
It lasted for almost 3 million years.
Changes at the level of the oceans
During this time there were profound and significant changes in the bodies of water. One of those known was the breakdown of communication between the Atlantic and Pacific oceans, a consequence of the emergence of the Isthmus of Panama.
Likewise, the basin of the Mediterranean Sea was once again filled with water from the Atlantic Ocean, ending the so-called Messinian salt crisis.
Appearance of the first bipedal hominid
According to the collected fossils, during the Pliocene epoch the first hominid appeared, which they named Australopithecus . This hominid was transcendental in the origin of the human species, since it originated the first specimens of the genus Homo.
During the Pliocene epoch there was no great orogenic activity, while continental drift continued. The continents continued their slow movement through the seas, even being just kilometers from their current location.
One of the most important milestones of this time is the formation of the isthmus of Panama, which holds North America together with South America. This was a transcendental phenomenon, geologically speaking, since it had an influence on the climate of the entire planet.
The closure of communication between the Pacific and Atlantic oceans resulted in a significant change in marine currents, causing a cooling of both oceans, but especially the Atlantic.
At the level of the poles, Antarctic and Arctic waters experienced an abrupt drop in temperatures, becoming the coldest on the planet, a title they hold to this day.
Likewise, according to information gathered by specialists, during this time there was a notorious drop in sea level. This resulted in the emergence of pieces of land that are currently submerged.
Such is the case of the land bridge that connects Russia with the American continent. Currently this is submerged, occupied by the area known as the Bering Strait , so important in the theories of settlement of the American continent .
It is important to note that at the end of the previous period ( Miocene ), a phenomenon known as the Messinian salt crisis occurred, during which the Mediterranean Sea was closed due to the emergence of mountainous formations in what is now known as the Strait of Gibraltar. As a consequence of this, an extensive saline was formed in the space occupied by said body of water.
During the Pliocene epoch, the so-called Zancliense flood occurred, which consisted of the passage of water again from the Atlantic Ocean to the site occupied by the Mediterranean Sea.
How this event occurred is not entirely clear yet, as specialists have various theories. Some claim that it occurred abruptly, violently and unexpectedly, while others argue that a small gap formed in the barrier that separated the Mediterranean Sea from the ocean, which allowed a certain amount of water to pass through gradually.
Subsequently, the action of the water that flowed through that gap eroded it to form a small channel. The flow of water was maintained until the water levels stabilized and returned to normal in the Mediterranean Sea.
The climate throughout the time that this epoch lasted was quite diverse and fluctuating. According to the records collected by specialists in the area, there were times when the temperature increased considerably, as well as there were certain periods, especially at the end of the season, in which the temperatures decreased significantly.
One of the characteristics of the climate of this time is that it was seasonal. This means that it had stations, two of which were very well marked; a winter one, in which the ice spread notably, and a summer one in which the ice melted and gave way to arid landscapes.
In general, it can be said that the climate at the end of the Pliocene was quite arid and dry, causing the environment to change, transforming forests into savannas.
During this time the fauna diversified widely, being able to colonize various environments, while the flora suffered a kind of regression and stagnation, due to the prevailing climatic conditions.
In the Pliocene epoch, the plants that proliferated the most were grasslands. This was because they can easily adapt to low temperatures, and that was the climate that predominated in the Pliocene.
Likewise, there was a little tropical vegetation, represented by jungles and forests that were limited to the equatorial region, since there if the climatic conditions existed for them to prosper.
In the same way, thanks to the climatic changes of this time, large areas of arid land made their appearance that became deserts, some of which are still prevalent today.
In the areas near the poles, the same type of flora that abounds today was established; conifers. These have the ability to resist and thrive in environments where temperatures are quite low.
In the same vein, the tundra biome also spread across the northern polar regions. This distribution has remained this way up to the present, since the tundra extends in the borderlands with the North Pole.
One of the greatest milestones in human development occurred in the Pliocene: the emergence of the first hominid, Australopithecus . Likewise, mammals experienced great evolutionary radiation, finding themselves in a large number of environments.
Other groups of animals underwent certain changes. However, mammals were definitely the ones that stood out.
During the Pliocene, mammals began to settle in the places where they inhabit today.
They are an ancient clade of mammals whose main characteristic is that they walk supported by the tips of the fingers, which are covered by hooves.
There were species belonging to the ungulates that began to lose limbs and ground, such as camels or horses. However, in certain regions they managed to adapt and prosper.
This is a group of animals that are characterized by having an extension on their faces, which is called the proboscis. During the Pliocene, there were several specimens of this group, such as elephants and stegodons. Of these, only the former managed to survive and persist to the present day.
They are a group of mammals that are characterized by the fact that their incisor teeth are highly developed and are ideal for gnawing on wood or other materials. They are also quadruped and of varied size. They were widely distributed throughout the European continent.
The Australopithecus was homínido primate characterized by bipedal way around (in the two hindlimbs). They were small in stature, about 1.30 meters, and of slim build.
They were omnivorous, which means that they fed on both plants and animals. They mainly thrived on the African continent, where most of the fossils have been found.
The evolution of some reptiles , such as snakes, was linked to that of other groups of animals that constituted their food source. Likewise, fossils of alligators and crocodiles have been found in various regions of the planet, which seems to indicate that they were widely distributed.
However, specialists have established that in the European continent they had become extinct, as a result of the climate change that crossed that continent.
Among the birds were some specimens of the so-called “terror birds”, which inhabited the American continent and were predators of a large number of animals.
However, during this time they were already in decline. Other types of birds also inhabited during the Pliocene, such as the anseriformes, a group to which ducks and swans belong, among others.
The Pliocene epoch is divided into two ages:
- Zancliense: it was the first age of the Pliocene. It spanned approximately 2 million years. It is named after the ancient name of the city of Messina, Zancia.
- Piacenzian: it was the last age of the Pliocene. It began 3.8 million years ago and ended 2.7 million years ago. It owes its name to the Italian city of Piacenza.
- Gradstein, FM; Ogg, JG & Smith, AG; 2004 : A Geologic Time Scale 2004 ,
- Pliocene Epoch. Retrieved from: Britannica.com
- The Pliocene epoch. Obtained from: ucmp. Berkeley.
- The Pliocene epoch (5-16 million years ago). Retrieved from: australiammuseum.net
- Van Andel, Tjeerd H., New Views on an Old Planet: a History of Global Change (second edition, 1994)