Era
Millions of
years ago
Cenozoic
Period
Quatemary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
1.6
66.4
144
208
Mesozoic
286
Carboniferous
Pennsylvanian
Mississippian
320
360
Paleozoic
408
Devonian
Silurian
Ordovician
Cambrian
Precambnan
570
Which method is most likely used to identify what happened before the start of the Paleozoic era?