Which statement best describes how scientists date fossils when radiometric methods aren't available?

• A. They use carbon dating anyway.
• B. They guess randomly.
• C. Scientists turn to stratigraphy to estimate the age of a fossil based on the age of the strata in which it is found.
• D. They measure the fossil's weight.

Answer: (C)

When radiometric clocks aren’t available, scientists date fossils by looking at the rock layer they’re found in—stratigraphy. In an undisturbed sequence, layers form in a time-ordered stack, with newer material laid down atop older layers. So a fossil’s age is inferred from the age of the surrounding sedimentary strata. By comparing that layer to others across the region and using markers like distinctive ash beds or index fossils—species that existed for a known, short time period—we can place the fossil within a relative time frame. This approach gives a credible sense of when the organism lived even without exact years. Carbon dating is not used here because it only works for relatively recent, organic material and isn’t reliable for most fossils.