The Ice Age lasted around one hundred thousand years from about 110,000 to 10,000 years ago. The ice grew and retreated over this time but the largest extent of ice glaciers was around 18,000 years ago. The ice covered most of the northern hemisphere and some ice even got into the southern hemisphere. There were huge ice sheets covering North America, Eurasia, and Antarctica, most of Canada, New Zealand and Tasmania, as well as huge ice caps on all the world’s mountains.
Many animals could not adapt to the freezing conditions and died out, but amazingly, many others did adapt and survive. Some of them still live on Earth today. Some evolved into modern animals. Other animals took evasive action avoiding the worst excesses of the Ice Age, and these animals are the same today as they were then.
One animal that survived the Ice Age is, the one we never count, the human animal; Neanderthal man survived the Ice Age. Heidelbergensis evolved physical adaptations to cold and became Neanderthal man. The tall physique of Heidelbergensis became the Neanderthal’s shorter, stockier body, which was ideal for conserving heat. Neanderthals also became very muscular to cope with the rigours of living in the Ice Age. Neanderthal children grew faster than modern children do; an eight-year-old Neanderthal child was as developed as a twelve-year-old homosapien is. Experiments at Loughborough University show that the Neanderthal shape was better adapted at dealing with cold than the shape of modern humans. Neanderthals were skilled hunters, and omnivores and those animals that survived the Ice Age tended to be those who could eat a wide range of foods.
Some animals changed other attributes to survive the Ice Age. Some animals, such as mammoths and mastodons developed changes in their teeth in order to eat different kinds of vegetation. These were also very large animals, and their sheer size helped them to retain heat and animals such as mammoths grew long thick oily coats. Mammoths’ ears and tails shrunk. Scientists recently discovered  that mammoths’ blood also changed during the Ice Age. Their haemoglobin, the protein in red blood cells that delivers oxygen to the tissues, evolved to release oxygen more easily in the cold. It is possible that other animals made similar adaptations to help them live in the cold. The mammoth’s closest living relative is the Asian elephant and they do not have this adaptation. It is likely that other large mammals may have adapted similarly. Other creatures may also have adapted their bodies to cope with the Ice Age. There is an Antarctic fish called chionodraco hamatus, which has a kind of natural antifreeze in its blood.
Some animals coped by moving south, for example, the Jaguar moved down from the southern United States into Mexico and Central America. Crocodiles are remnants of the dinosaur age and lived through the Ice Age because they lived in the warmer climates near to the equator. Polar, grizzly and brown bears all survived the Ice Age, as did musk ox, red deer, reindeer, bison. The Arctic hare and Arctic fox are also, unsurprisingly, remnants from the Ice Age. Small mammals such as muskrats, raccoons, stoats, opossum, and flying and fox squirrels also lived through the Ice Age.
Some of the tiniest creatures also survived - insects, dragonflies and spiders. Spiders are very interesting because they can alter their whole metabolism to ensure their survival in all kinds of extreme conditions. In Greenland today, there are 320 species of native insects, including several butterflies, which shows that even the tiniest creatures can adapt to extreme cold.
In the oceans, many creatures survived the Ice Age - sponges, corals, starfish, clams, sharks, turtles and the coelacanth. Many familiar birds, such as bald and golden eagles, black vultures and some woodpeckers also flew in Ice Age skies.
A surprising number of familiar species survived the Ice Age. Others like the wooly mammoth and the Neanderthal adapted well to the Ice Age, but they could not adapt to the earth’s warming afterwards. Animals survived the Ice Age by various means; some ran from the cold and some adapted to survive.
 Published in the journal “Nature Genetics”