Thinking Scientifically

1. What are the limitations, if any, of the recent evidence used to support cosmic ancestry?

2. How was the scientific method used to show that life does not arise spontaneously?

3. Louis Pasteur is often credited with disproving the theory of spontaneous generation. Stanley Miller often receives credit for “brewing” primordial soup. What previous discoveries and hypotheses influenced Pasteur and Miller?

4. What is the chemical evidence that life may have originated in different ways?

5. Why does molecular evidence usually yield an earlier date of a speciation even than fossil evidence?

6. What might have happened to evolving life between the first types of progenotes, and the last common ancestor that the three domains of life shared?

Additional Questions and Terms

1. The following chart lists the compounds that Stanley Miller obtained in his original prebiotic simulation experiment, and the same compounds identified in the Murchison meteorite. The dots represent the relative amounts of the various chemicals. Develop two hypotheses to explain these results.

2. The study of the origin of life requires speculation because the oldest fossils have probably been destroyed. Moreover, we cannot know if biochemical experiments to re-create conditions on the early Earth are accurate. Do you think that because of these uncertainties we should abandon research on the origin of life? Cite reasons for your answer.