The Fossil Record

Key Questions

  • Answer:

    It shows homologous structures.


    A homologous structure is a structure in organisms that shows that they used to be the same species a long time ago and have since diverged.

    This can be seen in animals like humans and whales. Human hands and whale flippers have extremely similar bone structures. This leads scientists to believe that both species used to be one species.

  • Answer:

    The idea that continental drift has taken place came up primarily because of study of fossils discovered from different corners of earth.


    The word 'fossil' was coined more than 500 years ago, by German scientist Georgius Agricola, though records describing fossils are much older. It actually means 'having been dug up' in its original latin form.

    In prechristian era, Greek philosophers discussed about fossils, later Leonardo da Vinci studied fossils in great detail so that he is today regarded as Father of Palaeontology. But it was Robert Hooke, author of Micrographia, who first realised that fossils are evidences of past life and more:

    ...if the finding of Coines, Medals, Urnes, and other Monuments of famous persons, or Towns, or Utensils, be admitted for unquestionable Proofs,that such Persons or things have, in former times had a being, certainly those Petrifactions may be allowed to be of equal Validity and Evidence, that there have formerly been such Vegetables or Animals... and are true universal Characters legible to all rational Men.

    Before enlisting specific fossils which allow us to speculate the details of continental drift that has taken place on earth, let us see how the continents were arranged during mesozoic era .


    Let us now focus on fossils which prove existence of Gondwanaland.

    • One type of fern, the Glossopteris , arose and flourished in southern hemisphere before becoming extinct in Permian.

    Geologist Israel C White was the first person to report the similarities between coal (fossilised plants) found in Brazilian mines and that found in Africa. His insight helped Alfred Wegener to publish continental drift theory in 1912.

    • Fossils of reptile Lystrosaurus, which roamed the earth 250 million years ago: excavated and recovered from South Africa, India and Antarctica: therefore leaving no doubt that the three continental entities were once joined.

    • Another significant evidence comes in the form of Mesosaurus, reported from both South America and South Africa. The two continents are today separated by very vast Atlantic ocean.


  • Answer:

    The fossil record is an incomplete history of life because not everything fossilizes.


    For the fossil record to be a complete reference for past life, we'd need to have a record for every organism that ever lived on the planet. Fossils are very rare. Not every organism will turn into a fossil because the process of fossilization requires very specific environmental, geological, and biological conditions.

    While we do have fossils of organisms from long ago, such as our human ancestors, dinosaurs, and trilobites, that's a lot of time to cover and there are many organisms we haven't discovered.
    If you click here , you can see a larger version of this image.

    Here's a link to learn more about how fossils form: How do fossils form?