Question

Using the "Checkpoints Section" of your eBook answer the following question:

What types of evidence allow scientists to infer that single-celled life likely existed 3.8 billion years ago? Select all that apply.

Group of answer choices

evidence of extinction events

transitional fossils in ancient rocks

fossil evidence, such as stromatolites

certain forms of carbon in ancient rock

Answer 1

The types of evidence that allow scientists to infer that single-celled life likely existed 3.8 billion years ago include:

- **Fossil evidence, such as stromatolites**
- **Certain forms of carbon in ancient rock**

These pieces of evidence suggest the presence and activities of early microorganisms.