OVERPOPULATION

 The quaternary period began 2.6 million years ago and extends into the present. The quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy. This period is divided into two epochs: the Pleistocene (2.588 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today). The informal term "Late Quaternary" refers to the past 0.5–1.0 million years. https://en.wikipedia.org/wiki/Quaternary

THE PLEISTOCENE: Often colloquially referred to as the Ice Age, is the geological epoch which lasted frim about 2,588,000 to 11,700 years ago, spanning the world´s most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The Pleistocene  is divided into four stage ora ges, the Gelasian, Calambrian, Ionian and Tarantian. https://en.wikipedia.org/wiki/Pleistocene

Imagen 1: Pleistocene map

Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places. It is estimated that, at maximum glacial extent, 30% of the Earth's surface was covered by ice. In addition, a zone of permafrost stretched southward from the edge of the glacial sheet, a few hundred kilometres in North America, and several hundred in Eurasia.

Imagen 2: The largest land mammals of the Pleistocene

One of the largest land mammals of the Pleistocene, was the Mamut,on the time period that spanned from 2.6 million to 11,700 years ago.* Pleistocene biotas were 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 was also characterized by the presence of distinctive large land mammals and birds.

Mammoths and their cousins the mastodons, longhorned bison, saber-toothed cats, giant ground sloths, and many other large mammals characterized Pleistocene habitats in North America, Asia, and Europe. Native horses and camels galloped across the plains of North America. Great teratorn birds with 25-foot wingspans stalked prey. Around the end of the Pleistocene, all these creatures went extinct.

Imagen 3: The largest land animals of the Pleistocene

The Pleistocene also saw the evolution and expansion of our own species, Homo sapiens, and by the close of the Pleistocene, humans had spread through most of the world. According to a controversial theory first proposed in the 1960s, human hunting around the close of the Pleistocene caused or contributed to the extinction of many of the Pleistocene large mammals. It is true that the extinction of large animals on different continents appears to correlate with the arrival of humans, but questions remain as to whether early human hunters were sufficiently numerous and technologically advanced to wipe out whole species. It has also been hypothesized that some disease wiped out species after species in the Pleistocene.

Paleocene Epoch

• Paleocene Epoch, also spelled Palaeocene Epoch, first major worldwide division of rocks and time of the Paleogene Period, spanning the interval between 66 million and 56 million years ago. The most complete picture of Paleocene terrestrial life and environments is afforded by the rock record of North America

The Paleocene is subdivided into three ages and their corresponding rock stages: the Danian, Selandian, and Thanetian.

• The Paleocene was "bookended" by dramatic events: A mass extinction (the Cretaceous-Tertiary extinction event) and a rapid global warming (the Paleocene-Eocene Thermal Maximum). The die-off of the dinosaurs in the prior mass extinction left unfilled ecological niches worldwide, and the name "Paleocene" comes from Greek and refers to the "old(er) (paleo)–new (ceno)" fauna that arose during the epoch, prior to the emergence of modern mammalian orders in the Eocene. The Paleocene provided the foundation for today, including the appearance of primate-like mammals.

Paleocene climate

• According to the science of paleoclimatology, the early Paleocene is considered to have been slightly cooler than the preceding Cretaceous, though temperatures rose again late in the epoch. The climate was warm and humid worldwide, with subtropical vegetation growing in Greenland and Patagonia. The poles were cool and temperate, North America, Europe, Australia, and southern South America were warm and temperate; tropical climates characterized equatorial areas, and north and south of the Equator, climates were hot and arid (Scotese 2002).

Paleocene flora

• Pine trees appeared during the Paleocene Epoch and avian species flourished and diversified.
• the Paleocene is marked by the development of modern plant species. Cacti and palm trees appeared. Paleocene and later plant fossils are generally attributed to modern genera, or to closely related taxa.
• Flowering plants (angiosperms), first seen in the Cretaceous, continued to develop and proliferate, coevolving with the insects that fed on these plants and pollinated them.

Paleocene fauna

• Paleocene animals, especially mammals, are lacking or rare or are only of late Paleocene age. Prominent faunal remains of the late Paleocene Epoch are known from the regions of Cernay, France; Gashato, Mongolia; and the Chico River of Patagonian Argentina.
• the complete absence of dinosaurs and other reptilian groups that were dominant during the preceding Cretaceous Period. 
• Paleocene mammals included Cretaceous species such as opossum-like marsupials and, especially, the archaic and unusual multituberculates—herbivorous animals that had teeth very similar in some respects to those of the later, more advanced rodents. 
•  Primates became more abundant in the middle Paleocene; they displayed characteristics intermediate between the insectivores and the lemurs, especially in their dental anatomy.
• mammals had evolved and widely populated the changing continental land-masses long before the Paleocene Epoch, the reduction in predator species allowed land mammals to dominate and thrive—eventually setting the stage from the evolutionof homo sapiens (humans). Pine trees appeared during the Paleocene Epoch and avian species flourished and diversified.
• Mammals of the Paleocene include:
  • Monotremes. Three species of monotremes are represented in modern times: The duck-billed platypus, and two species of Echidnas. Monotrematum sudamericanum lived during the Paleocene.
  • Marsupials. A number of marsupials are represented in modern times, such as the kangaroos, which are characterized by giving birth to embryonic babies, who crawl into the mother's pouch and suckle until they are developed. The Pucadelphys andinus is a Paleocene example of a marsupial.
  • Multituberculates. This is the only major branch of mammals to go extinct. This rodent-like grouping includes the Paleocene Ptilodus.
  • Placentals. This grouping of mammals became the most diverse and the most successful. Members include hoofed ungulates, primates, and carnivores, such as the Paleocene mesonychid.

Birds

Birds began to diversify during the epoch, occupying new niches. Most modern bird types had appeared by mid-Cenozoic, including perching birds, cranes, hawks, pelicans, herons, owls, ducks, pigeons, loons, and woodpeckers.

Large, carnivorous, flightless birds (also called Terror Birds) have been found in late Paleocene fossils, including the fearsome Gastornisin Europe.