The Kerma culture was an early civilization which flourished from around 2500 BC to about 1600 BC in Nubia, present day Sudan, centered at Kerma. It seems to have been one of a number of Sudanese states during the Middle Kingdom period of Ancient Egypt. In its latest phase, lasting from about 1700-1500 BC, it absorbed the Sudanese kingdom of Sai and became a sizable, populous empire rivaling Egypt. Around 1500 BC, it was absorbed into the Egyptian Empire, but rebellions continued for centuries. By the 11th century BC, the more 'Egyptianized' Kingdom of Kush emerged, apparently from Kerma, and regained the region's independence from Egypt.
Question: When civilization occurs?
Answer: 2500 BC