Editor's note: This is a historical chronology principally devoted to marking milestones in human scientific achievement or observation. Detailed information related to the eons, eras, periods, and epochs of geologic time may be found in text and diagrams related to the topic Geologic time.

c.4,600,000,000 B.C.
Origin of Earth: 4,600 million years ago (mya).

c.4,000,000 B.C.
Earliest hominid species appear on Earth.

c.50,000 B.C.
Homo sapiens sapiens emerges as a conscious observer of nature.

c.30,000 B.C.
Stone Age cultures use pigments to color various artifacts.

c.10,000 B.C.
Neolithic Revolution: transition from a hunting and gathering mode of food production to farming and animal husbandry, that is, the domestication of plants and animals.

c.4000 B.C.
Early applied chemistry begins in Egypt with the extraction and working of metals, including copper, tin, and bronze. Egyptians are also familiar with eye paint and plaster...