The 31st century BC is a century which lasted from the year 3100 BC to 3001 BC.
c. 3100 BC: Narmer (Menes) unifies Upper and Lower Egypt into one country; he rules this new country from Memphis.
c. 3100 BC: Predynastic period (Neolithic) ends in Ancient Egypt (other date is 3150 BC).
c. 3100 BC: Early Dynastic (Archaic) period starts in Ancient Egypt (other date is 3150 BC).
c. 3100 BC: The first temple of Tarxien is in use by the Neolithic inhabitants of Malta.
c. 3100 BC: First stage in the construction of Stonehenge.
c. 3100 BC – 2600 BC: Skara Brae, Orkney Islands, Scotland is inhabited.
c. 3100 BC: Humans develop their first writing system, cuneiform script.
c. 3051 BC: The oldest currently living organism, a Pinus longaeva, undergoes germination in the White Mountains of California. It is still present to this day.
Scorpion II, presumably the last pre-dynastic pharaoh of ancient Upper Egypt
Narmer, founder of the first dynasty of Egypt
Hor-Aha, the second pharaoh of the First dynasty of Egypt
Djer, the third pharaoh of the First dynasty of Egypt
Ötzi, the oldest natural mummy ever found in Europe, lived around this time.
Drainage and sewage system in the Indus Valley
Dams, canals, stone sculptures using inclined plane and lever in Sumer and the Tigris-Euphrates Valley
Copper was in use, both as tools and weapons
Senet is one of the oldest known board games in the world.
c. 3100 BC – Invention of writing in Mesopotamia and Egypt
31st century BC Wikipedia (Text) CC BY-SA