Final answer:
The fossil record helps scientists to estimate a species' average lifespan, providing a baseline for assessing human impact on biodiversity.
Step-by-step explanation:
Scientists have used the fossil record to estimate the average length of time that a species inhabits the Earth. This estimate is very useful for assessing the impact of humans on the Earth's biological diversity as it offers a baseline for comparison. If the average species has had a lifespan of around 1-10 million years, we can begin to understand the significant impact human activities may have on accelerating the extinction rates of many species.
The molecular clock technique complements the fossil record by providing dates for when species diverged, adding to our ability to chart the history of life. By understanding the history and patterns within the geologic time scale, we gain insight into the natural fluctuations in diversity and can measure them against the rapid changes spurred by human activity.