Darwin theorized that evidence for the evolution of new species can be found in homologous body structures. which observation supports this theory? a. the beaver and the capybara are similar species that inhabit similar environments in separate continents. b. the size, shape, and variety of squid, octopi, and chambered nautiluses have changed over time. c. the limbs of reptiles, bird, and mammals resemble the fins of the ancient lobe-finned fish. d. the embryos of many animals with backbones are very similar.