Doggerland is a "lost land" that existed in the present-day North Sea, between England, the Netherlands, and Denmark. Doggerland existed towards the end of the last Ice Age, about 11,000 years ago, when glacial ice in northern Europe had melted but sea levels were still low enough that the area was not flooded as it is today. Sea levels were about 120 m (394 ft) below current levels. Other areas around the world that were made dry by these sea levels include seas around Indonesia and the Bering Strait, which was crossed by hunter-gatherers into the Americas.
Doggerland was a rich habitat in its heydey, a paradise for humans and other animals. Being a low-lying area, it had abundant swampland and water for drinking, and was frequented by many animals. It formed a land bridge from mainland Europe to England and the rest of the United Kingdom. Southern Britannia was intermittently occupied by humans during the Mesolithic, but the most populated area appears to have been Doggerland. By mapping the geologic makeup of the floor of the North Sea, scientists have discovered submerged features such as hills, valleys, and riverbeds. The bed of the largest submerged largest river, similar in size to the present-day Rhine, has been named Shotton River after Birmingham geologist Richard Shotton.
The Doggerland region is considered crucial for understanding the Mesolithic (Middle Stone Age) period in northern Europe. The region is named after the Dogger Bank, a 20 m (65 ft) tall sand bank submerged in the North Sea, a moraine (accumulation of debris) created by glacial action. Scientists have studied Doggerland using AUVs (autonomous underwater vehicles) and divers, finding various tools including hand-axes, primitive boats, carved antlers, and human remains, including bones. These bones have been studied to analyze the diet of the humans that lived there.
Doggerland used to be occupied by mammoths, saber-toothed tigers, deer, and even lions. You can't really expect any domesticated animal in the list, since the circumstances won't really make that a possibility. Subfossilized bodies of these animals are sometimes uncovered by bottom-trawling fishing ships. It is thought that the area was relatively empty before 13,000 years ago, when a cold snap would have turned the area into frigid tundra, but after that, the climate began to warm up and the area got friendlier to life. About 10,000 years ago, the Ice Age finally ended, and the water levels began to rise. The rise would have been slow -- about one or two meters per century -- but by the time it was done, Doggerland was under water, and Britain became an island, which had occurred by about 8,000 years ago.