Understanding Evolution

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Understanding Evolution

Evo 101

Home → Important events in the history of life (text-only version)

    Important events in the history of life (text-only version)

    View the Graphical timeline

    A timeline can provide additional information about life’s history not visible on an evolutionary tree. These include major geologic events, climate changes, radiation of organisms into new habitats, changes in ecosystems, changes in continental positions, and major extinctions. Explore the timeline below to view some of the major events in life’s history.

    Years ago Event
    130,000 Anatomically modern humans evolve. Seventy thousand years later, their descendents create cave paintings — early expressions of consciousness.
    4 million In Africa, an early hominid, affectionately named “Lucy” by scientists, lives. The ice ages begin, and many large mammals go extinct.
    65 million A massive asteroid hits the Yucatan Peninsula, and ammonites and non-avian dinosaurs go extinct. Birds and mammals are among the survivors.
    130 million As the continents drift toward their present positions, the earliest flowers evolve, and dinosaurs dominate the landscape. In the sea, bony fish diversify.
    225 million Dinosaurs and mammals evolve. Pangea has begun to break apart.
    248 million Over 90% of marine life and 70% of terrestrial life go extinct during the Earth’s largest mass extinction. Ammonites are among the survivors.
    250 million The supercontinent called Pangea forms. Conifer-like forests, reptiles, and synapsids (the ancestors of mammals) are common.
    360 million Four-limbed vertebrates move onto the land as seed plants and large forests appear. The Earth’s oceans support vast reef systems.
    420 million Land plants evolve, drastically changing Earth’s landscape and creating new habitats.
    450 million Arthropods move onto the land. Their descendants evolve into scorpions, spiders, mites, and millipedes.
    500 million Fish-like vertebrates evolve. Invertebrates, such as trilobites, crinoids, brachiopods, and cephalopods, are common in the oceans.
    555 million Multi-cellular marine organisms are common. The diverse assortment of life includes bizarre-looking animals like Wiwaxia.
    3.5 billion Unicellular life evolves. Photosynthetic bacteria begin to release oxygen into the atmosphere.
    3.8 billion Replicating molecules (the precursors of DNA) form.
    4.6 billion The Earth forms and is bombarded by meteorites and comets.
    You’ve reached the end of this section, but if you’d like to continue reading through Evolution 101, go back to the Graphical timeline and click the next button. Or you can go back to the Evolution 101 cover page.

    Read more about the origins of life on Earth with this advanced tutorial or about human evolution in this brief summary.

    To learn more about the formation of the Earth, the building blocks of life, and the conditions required for life to arise, visit A Place for Life: A special astronomy exhibit of Understanding Evolution.

    To get a more detailed timeline of the history of life and learn more about deep time in general, visit the ChronoZoom Time Atlas of Earth History and Big History.

    Learn more about the origin of life in context: From the origin of life to the future of biotech: The work of Andy Ellington, a research profile.

    Learn more about human evolution in context: When it comes to evolution, headlines often get it wrong, a news brief with discussion questions.

    Teach your students about timelines: A long time, a classroom activity for grades K-2.

    Teach your students about the history of life: What came first?, a classroom activity for grades 6-8.

    Find additional lessons, activities, videos, and articles that focus on the history of life.