4.5 billion B.C.
Planet Earth formed.
3 billion B.C.
First signs of primeval life (bacteria and blue-green algae) appear in oceans.
600 million B.C.
Earliest date to which fossils can be traced.
4.4 million B.C.
Earliest known hominid fossils (Ardipithecus ramidus) found in Aramis, Ethiopia, 1994.
4.2 million B.C.
Australopithecus anamensis found in Lake Turkana, Kenya, 1995.
3.2 million B.C.
Australopithecus afarenis (nicknamed “Lucy”) found in Ethiopia, 1974.
2.5 million B.C.
Homo habilis (“Skillful Man”). First brain expansion; is believed to have used stone tools.
1.8 million B.C.
Homo erectus (“Upright Man”). Brain size twice that of Australopithecine species.
1.7 million B.C.
Homo erectus leaves Africa.
100,000 B.C.
First modern Homo sapiens in South Africa.
70,000 B.C.
Neanderthal man (use of fire and advanced tools).
35,000 B.C.
Neanderthal man replaced by later groups of Homo sapiens (i.e., Cro-Magnon man, etc.).
18,000 B.C.
Cro-Magnons replaced by later cultures.
15,000 B.C.
Migrations across Bering Straits into the Americas.
10,000 B.C.
Semi-permanent agricultural settlements in Old World.
10,000–4,000 B.C.
Development of settlements into cities and development of skills such as the wheel, pottery, and improved methods of cultivation in Mesopotamia and elsewhere.
5500–3000 B.C.
Predynastic Egyptian cultures develop (5500–3100 B.C.); begin using agriculture (c. 5000 B.C.). Earliest known civilization arises in Sumer (4500–4000 B.C.). Earliest recorded date in Egyptian calendar (4241 B.C.). First year of Jewish calendar (3760 B.C.). First phonetic writing appears (c. 3500 B.C.). Sumerians develop a city-state civilization (c. 3000 B.C.). Copper used by Egyptians and Sumerians. Western Europe is neolithic, without metals or written records.
3000–2000 B.C.
Pharaonic rule begins in Egypt. King Khufu (Cheops), 4th dynasty