" First, the relative age of a fossil can be determined.
Relative dating puts geologic events in chronological order without requiring that a specific numerical age be assigned to each event.
For example, based on the primate fossil record, scientists know that living primates evolved from fossil primates and that this evolutionary history took tens of millions of years.
By comparing fossils of different primate species, scientists can examine how features changed and how primates evolved through time.
Most sediment is either laid down horizontally in bodies of water like the oceans, or on land on the margins of streams and rivers.
Each time a new layer of sediment is deposited it is laid down horizontally on top of an older layer.
Erosion could also take a mineral or fossil out of position and place it in another layer, thus causing humans to incorrectly assume an older or different age.In the example above, Sandstone B is younger than Sandstone A.Because relative dating doesn't give you an absolute age, errors are much less common in comparison to absolute dating.The age of the fossil must be determined so it can be compared to other fossil species from the same time period.Understanding the ages of related fossil species helps scientists piece together the evolutionary history of a group of organisms.