Tracking History: The Evidence for Evolution

If two different species have similar bone structures despite using them for different tasks, then they likely inherited that design from a common ancestor. If they shared an ancestor, then this serves as evidence for evolution.

If a species is evolving from a land dweller to a sea dweller, then there should be fossils with features of both. If these "bridge" fossils exist, then they are defined as transitional fossils.

If two species have very similar DNA sequences, then they have had less time to drift apart since sharing a common ancestor. If genetic similarity points to shared history, then it is molecular evidence for evolution.

If a human embryo and a chicken embryo both have gill slits and tails in early development, then they likely share an ancient genetic program. If they share this program, then they share a common ancestor.

If similar species are found in the same geographic region (like various lemurs in Madagascar), then they likely evolved from a single ancestor that lived there. If location patterns match ancestry, then it is evidence for evolution.

If homology is based on shared ancestry and analogy is based on shared function in different lineages (like insect wings vs. bird wings), then their origins are the primary difference.

If every living organism on Earth uses the same molecule (DNA) and the same bases to store information, then it is highly likely they all descended from a single original source.

If fossils are formed by burial, then they must be trapped in materials that accumulate in layers. If sand and mud turn into stone, then the result is sedimentary rock.

If vastly different animals start their lives with the same physical features, then they are using a shared genetic "recipe." If they share a recipe, then they share a common ancestor.

If fossils provide a timeline of change and homologies show shared blueprints, then they both support the idea of descent with modification. If they support this idea, then they are evidence for evolution.

If an organism dies and its hard parts are buried in sediment and mineralized over millions of years, then it creates a permanent record. If this record is a physical remains or trace, then it is a fossil.

If a bird wing and a bat wing share the same basic bone pattern (humerus, radius, ulna), then they are structurally related. If structures share an origin but have different functions, then they are examples of homology.

If two structures perform the same job (flying) but are built differently and have no common ancestor with wings, then they are not homologous. If they are functional but separate in origin, then they are analogous.

If fossilization requires very specific conditions (rapid burial, hard parts), then many soft-bodied organisms never leave a trace. If many organisms are lost to history, then the record is "incomplete" but still provides a clear timeline.

If a shark and a dolphin both have streamlined bodies but come from different ancestors, then they arrived at the same solution independently. If they "converged" on the same trait, then it is convergent evolution.

If many vertebrates share a "five-fingered" limb plan regardless of whether they swim, fly, or walk, then they share a common skeletal blueprint. If this blueprint is the five-digit plan, then it is the pentadactyl limb.

If new sediment is always deposited on top of old sediment, then the bottom layers must be the oldest. If we use this to date fossils, then we are applying the Law of Superposition.

If a structure exists in a species but no longer serves its original purpose or has no function at all, then it is vestigial. If humans have tailbones but no tails, or whales have hip bones but no legs, then those are vestigial.

If life has changed over time, then the oldest rocks should hold the simplest life. If the fossil record shows a progression from simple to complex and a history of extinction, then it supports evolution.

If whale fossils show reduced leg bones and a shifting blowhole, then it proves they transitioned from land to sea. If they were land mammals, then they never had gills, making E incorrect.