Dating geologic time
Understanding the ages of related fossil species helps scientists piece together the evolutionary history of a group of organisms.
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.
The latest high-tech equipment permits reliable results to be obtained even with microscopic samples.
Radiometric dating is self-checking, because the data (after certain preliminary calculations are made) are fitted to a straight line (an "isochron") by means of standard linear regression methods of statistics.
However, by itself a fossil has little meaning unless it is placed within some context.
The age of the fossil must be determined so it can be compared to other fossil species from the same time period.
These changes typically occur so slowly that they are barely detectable over the span of a human life, yet even at this instant, the Earth's surface is moving and changing.Online exhibits Geologic time scale Take a journey back through the history of the Earth jump to a specific time period using the time scale below and examine ancient life, climates, and geography.You might wish to start in the Cenozoic Era (65.5 million years ago to the present) and work back through time, or start with Hadean time (4.6 to 4 billion years ago)* and journey forward to the present day it's your choice. The three million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.
The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time, and is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history.
By comparing fossils of different primate species, scientists can examine how features changed and how primates evolved through time.