ASP PLZ Study the diagram of the geologic time scale.
Which method is most likely used to identify what happened before the start of the Paleozoic era?
1) Scientists study fossils from the Jurassic period.
2) Scientists observe index fossil records of the Mesozoic era.
3) Scientists examine fossil evidence during the Precambrian time.
4) Scientists explore the emergence of mammals and humans in the Cenozoic era.