Technically there have been many ‘Ice Ages’ in our geological past, but the most recent glacial period happened during the Pleistocene, from approximately 110,000 to 10,000 years ago. Interestingly enough, an ice age is where there is a long-term reduction in the Earth’s temperature, resulting in the polar ice caps to be present or expand. So, in this way, we are still in an ice age that began 2.6 million years ago, simply because of the presence of the Arctic, Antarctic and Greenland ice sheets.
During this time, mammals were significantly bigger than their modern relatives but the harsh, cold climate led to the decline and extinction of these mega-fauna. The extinct animals will be described in this article:
Mammoths: the extinct genus Mammuthus had long, curved tusks. The northern species commonly had long hair, also. They lived from the Pleistocene, about 5 million years ago, to the Holocene, 4500 years ago. These creatures lived in Europe, Asia, Africa and North America and were members of the family Elephantidae. The word ‘mammoth’ was first used to describe anything that was huge, which is what mammoths indeed were; the largest known species were 4m tall and weighed up to 8 tonnes, even though some sizable males weighed up to 12 tonnes! Both sexes had tusks, which is quite unusual. They were pregnant for the long period of 22 months and gave birth to only one calf.
The woolly mammoth (M. primigenius) was the last species to die out. It seemed that they all died out 10000 years ago in a mass extinction of the mega-fauna. It is still unsure as to why they went extinct. It may have been because of the warming during the Holocene, leading to the decline in the glaciers and sea level rise. This caused there to be more grassland environments, and not forests that the mammoths lived in. But, these kinds of warming periods had already happened during the ice age and it hadn’t led to the extinction of mega-fauna. Other causes might have been from infectious diseases or overhunting from humans.
Mastodons: these are related to elephants and lived in North and Central America and went extinct also in the Pleistocene about 10000 to 11000 years ago. These were also forest dwellers and lived in herds, which may too have gone extinct because of climate change and hunting, particularly by the Clovis hunters. The word ‘mastodon’ means nipple tooth because of their cone-shaped cusps of their teeth, which looked like nipples. They were similar in appearance to mammoths and elephants, although they are not closely related. In comparison to mammoths, they had shorter legs, a longer body and more heavily muscled, similar to Asian elephants. The males could reach up to 2.8m high and could weigh up to 4.5 tonnes. Their tusks were curved, supported by a low and long skull.
Saber-toothed cats: Machairodontinae are a subfamily of true cats that went extinct in the Pleistocene. Included in this subfamily was the famed genus Smilodon, which I will describe here. Several fossils have been found with one of the largest collections taken from the La Brea Tar Pits. Three species of the genus are known and they vary in size and build. They were a lot more robust than any other modern big cat and their defining feature being the long upper canines, reaching up to 28cm in length. Its jaw had a much bigger gape and its large teeth were made for precision killing. They fed on bison and camels. They probably lived in forest where they could hide and then ambush prey. It might have gone extinct because it fed only on large animals. Smilodon were about the same size as modern lions or tigers, but were built more like bears, and their brains were a lot smaller than other cats. It is suggested that although their gape is much bigger than other cats, and their teeth substantially great, their bite was only a third that of a lion’s. This is because instead they could grasp and latch onto their prey, and kill them that way.
Glyptodon: these large, armoured relatives of armadillos were roughly the same weight as a Volkswagen Beetle. They almost looked like turtles, with squat limbs and a round shell, reaching up to 3.3m in length. Their hard, protective shells were made up of more than 1,000 2.5 cm-thick scutes, with each species having its own unique plate pattern. Even the tail was armoured, and they had bony caps on top of their skulls. This animal was most probably hunted to extinction also.
Irish elk: these were one of the largest deer that ever existed and went extinct about 7700 years ago. Despite the name, it was not exclusive to Ireland and wasn’t closely related to elks and this is why the term ‘Giant Deer’ is often used. It was up to 2.1m tall and had the largest antlers of any cervid, weighing up to 40kg. Large specimens weighed 700kg in total. There have been many discussions as to why this large beast went extinct; some have put it down to over hunting, where others have even suggested that the animal’s large antlers disabled them from moving through forests. High amounts of calcium and phosphate were needed to sustain antler growth and maybe the lack of these minerals in their diets led to their downfall.
These animals, along with giant ground sloths, short-faced bears and cave bears went extinct in this time, which paved the way for much smaller mammals that we see today. Neanderthals also became extinct during this period. At the end of the last ice age, cold-blooded animals, smaller mammals like wood mice, migratory birds, and swifter animals like whitetail deer had replaced the mega-fauna and migrated north. It was most severe in North America, where camels and horses were completely wiped out in that region.
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