How do scientists know about what life was like before humans appeared?

Why is it to call the calvin cycle the light independent reactions vs the dark reactions

Which is an innovation of gymnosperms? gymnosperms are the first seed plants. gymnosperms are the first flowering plants. gymnosperms are the first vascular plants. gymnosperms are the first spore plants.

Dr. arenas is a scientist who has been trying to determine if increasing pressure will increase the sound that occurs when two chemicals explode. it measures the volume of the sound that occurs at the minimum pressure at which the explosion will occur. it then increases the pressure and measures the volume of the explosions that occur. what kind of investigation is the scientist conducting?