However, relative methods are , which is that if there are layers of deposits, those laid down first will be on the bottom and those laid down last will be on the top. However, geological strata are not always found to be in a neat chronological order.
When the bones of our early ancestors are found in the same geological strata as those of other animals that are known to have lived only during a specific time period in the past, we assume that these ancestors must also have come from that time.
This is referred to as dating by association with they underwent relatively rapid evolutionary changes that are identifiable in their teeth and other skeletal parts.
Their bones also were frequently found in association with our human and primate ancestors.
When that style of arrow point is found at another site, the archaeologist would assign the site and the arrow point an age of approximately 500 years.
Often cross-dating is the only method archaeologists have to determine the age of sites.