During most of the Pleistocene (1.8 million to 10,000 years ago), Europe had many unusual extinct animals, some of which are difficult to imagine today. Since the last Ice Age began about 2.58 million years ago, Eurasia and North America have undergone cycles of glaciation and corresponding interglacials, where continental glaciers covered much of the planet north of 50 degrees latitude, then receded to the far north. As a result, many of the extinct European faunas were adapted to the cold. These extinct animals often changed their characteristics during the glacial and interglacial periods: for instance, the cave bear had a tendency to be larger during glacials and smaller during interglacials.
Some of the distinctive Ice Age and interglacial extinct animals that existed in Europe were the European Hippopotamus (larger than present-day hippos), the cave bear (larger than the Brown Bear but thankfully vegetarian), the Giant Unicorn (Elasmotherium, a fast-running 20 ft-long giant rhinoceros), the straight-tusked elephant (flourishing in Europe during the interglacial periods), Deinotherium (an elephant, the third largest land mammal ever known to have lived), Dinofelis ("terrible cat," a saber-toothed cat, about the size of a jaguar), the Southern Mammoth (with long curved tusks), the Tenerife Giant Rat (almost a foot long; an example of island gigantism), and the Woolly Rhinoceros (with thorough protection from the cold of Ice Ages). The Asiatic Lion and the Cheetah also lived in Europe during prehistoric times.
In ancient times, hominids lived in Europe and are members of the group of extinct animals there. The most famous of the extinct animals who were hominids were the Neanderthals, which went extinct around the Strait of Gibraltar about 22,000 years ago. A few Neanderthal skulls have been found with an extensive admixture of features, which some scientists have argued suggests intermarrying. However, genetic tests on the human and Neanderthal genomes discourage the notion that there was any interbreeding between the groups at all.