Pleistocene Epoch

Recent Ice Ages; Death of Mega-fauna

The Pleistocene Epoch (2.58-0.012 Ma) is in the Quaternary Period of the Cenozoic Era. It occurs before the Holocene, and after the Pliocene Epoch.

The severe climatic changes during the ice age had major impacts on the fauna and flora.
- With each advance of the ice, large areas of the continents became totally depopulated, and plants and animals retreating southward in front of the advancing glacier faced tremendous stress.
- There has not been an ice-free period in the Arctic Ocean for 2.6 million years (although that may be quickly changing)
This is the time of the Last Glacial Maximum (LGM) in which glacial ice sheets were at their greatest extent.
- This process started around 33 kya and was greatest between 26.5 kya and 20 kya.

This was a cold, dry northern grassland biome dominated by highly productive grasses, forbs, and willow shrubs
It was the world's most extensive biome during the Middle Pleistocene (Ionian Age)
As the name indicates, this biome was inhabited by woolly mammoths, bison, horses, and other large herbivores
The Mammoth Steppe thrived for approximately 100,000 years without major changes, but then diminished to small regions around 12,000 years ago
- This biome probably decreased due to climate change and the loss of large megafauna from hunting by Homo sapiens
- The eastern Altai-Sayan mountains of Central Eurasia has a habitat that may represent the best modern analogy to the Mammoth Steppe

Right: A reconstruction of the Mammoth Steppe during the summertime

Pleistocene Arc Hypothesis

"Present-day, disjunct, fragments of dry forests in central tropical South America give evidence of a previously more continuous distribution during the Pleistocene that has been disrupted by dry-cold vs. humid-warm climatic cycles" (Mogni et al. 2015)

Pando

Probable origin of "Pando", a vast group of quaking aspens (Populus tremuloides) and the Earth's largest and probably oldest organism
The group of trees grow in Fishlake National Forest, east of Salt Lake City, UT
The organism comprises about 47,000 tree trunks, all connected underground as root offshoots, making this one large cloned organism.
Researchers have estimated that Pando originated between 80,000 to one million years ago.The most severe stress resulted from drastic climatic changes, reduced living space, and curtailed food supply

Above: "Pando" in the Fishlake National Forest, UT, USA

Extinction event of mega-fauna took place between 13.8–11.4 Ka (Faith 2013)

Quick disappearance seems to indicate a sudden catastrophic event such as human over-hunting or cosmic impact

Origin of the genus Homo around 2.4–2.3 Ma

Evidence that early hominids fed on underground storage organs (such as tubers), sedges, fruits, leaves, and bark, as well as invertebrates, honey, and vertebrate animals, whether scavenged or hunted (K. Sayers, Georgia State University)
Opportunistic foraging was probably optimal for early hominids diets.
Evidence of agriculture in present-day Israel from 23,000 year ago (Snir et al. 2015)
- 140 plant species present, including wild oat, barley, and emmer wheat along with 13 weed species that are common today.

└Lofverstrom et al. (2024) The importance of Canadian Arctic Archipelago gateways for glacial expansion in Scandinavia

Pollen analysis suggests dispersal of modern humans occurred during a major Pleistocene warming spell (Phys.org 22Sep2023)

How Do Ice Ages Start? And When Did The Current One Begin? (IFL Science 29June2023)
Scientists Reconstructed a 2 Million-Year-Old Ecosystem From Ancient DNA (Science Alert 8Dec2022)
Dead for 32,000 Years, an Arctic Plant Is Revived (NY Times 20Feb2012)
Pando, the world's oldest organism (Science Friday 28Apr2015); Google Map of Pando's location