Relative dating puts geologic events in chronological ... if an unidentified fossil is found in the same rock layer as an index fossil, the two species must have existed during the same period ...

Scientists currently don't have a technique for dating fossils like Lucy directly, but they can assign these fossils relative dates based on the age of layers ... in volcanic rock that can be ...

Relative dating puts geologic events in chronological ... if an unidentified fossil is found in the same rock layer as an index fossil, the two species must have existed during the same period ...