The human race has been around for at least a couple hundred thousand years, perhaps longer. However, we only invented writing in 5000 BCE, and even then, few people were literate and archival methods were very poor. Therefore, information of about 99% of our human history can only be retrieved through the study of artifacts and fossils. To understand where a given artifact fits into the scheme of history requires dating it with a reliable degree of precision. Luckily, there exist good methods to do so.

The earliest method of dating artifacts is to look at which strata of rock they are found within. There exist large databases that tell us which artifacts corresponding to which civilizations are found in certain layers of soil, often giving us context for dating an artifact. The business of archeology is careful for this reason - to accurately determine the layer in which the artifact is found, each layer must be removed carefully during the dig. Unevenness in the soil and rock can complicate dating by stratification.

Another method for dating artifacts is called typology, which simply means the study of types. In typology, a researcher studies the material of an artifact, its form, and its likely purpose. Due to technological necessity, more complex artifacts are newer than simpler artifacts, so often an artifact can be dated simply by looking what it is made of and how sophisticated a process went into making it. If the artifact is from a civilization that possessed written records, dating is even easier because there are textual clues as to which artifacts were produced during which eras.

The most powerful method of artifact dating is carbon-14 dating. Because this method only works on once living things, it can only be used to date organic artifacts or bits of organic material located next to the find. Carbon-14 is a carbon isotope, found in about one out of every trillion carbon atoms.

Organisms take in carbon-14 naturally while they are alive. When they die, they stop absorbing it. Because carbon-14 has a half-life of 5,000 years, it slowly decays and its frequency declines as the organic material is buried. Determining the exact quantity of carbon-14 in a sample can give a very close approximation of the date when it was created.