You are excavating fish fossils from a site that used to be a small lake bed about 7 million years ago. You know that the lake bed was cut off from the ocean about 8 million years ago. You've further established that one species of marine fish lived there until about 5 million years ago. You label the strata from top to bottom as A, B, and C. You excavate many complete fossils from the same species: a large number of fish fossils without spines from stratum A, many fossils of fish with small spines from stratum C, and many fish fossils with large spines from stratum D. I've sketched the outline of these fish and their strata below: An illustration of fish fossils in different strata. Given this evidence, is it most likely that the ancestor of these fish that first entered the lake had large spines, small spines or no spines?1. No spines - evolution is progress towards perfection, so spines can only be gained not lost.
2. Long spines - evolution can only produce loss not gain of information, so the ancestor must have had short spines.
3. No spines
4. Long spines
5. Short spines