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The human race has existed for at least one hundred thousand years, and perhaps even longer. However, writing was only invented in 5000 BCE, and even then, few people were literate and archival methods were very poor. Therefore, information of about 99% of the 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. To accurately determine this, each layer of soil must be removed, a process known as extraction, during the archaeological dig. The business of archeology is done in an extremely careful manner in order to provide the most accurate results; this is often very time consuming and can last days, months, or even years. Over the years, archaeologists have compiled their findings into large databases containing information about the types of artifacts that correspond with difference civilizations, and the types of soil in which they usually found.
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 most likely purpose. Due to technological necessity, more complex artifacts are newer than simpler artifacts, so often an artifact can be dated simply by looking the materials and process used to make it. If the artifact is from a civilization that possessed written records, dating is even easier because there are existing textual clues as to which artifacts were produced during which eras.
One of the most commonly used methods of artifact dating is carbon-14 dating, also known as radiocarbon dating. This method only works to date organisms that were once alive no more than 58,000 to 62,000 years ago. By dating an organism sample found near the original found artifact, archaeologists can learn information about the artifact's time period and history.
Organisms take in carbon-14 naturally while they are alive, but when they die, they stop absorbing it. Carbon-14 has a half-life of 5,000 years, so 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 corresponding artifact's creation date.