Free webinar: Fossils reveal a rapid explosion of life on earth Depiction of an ocean community from the Cambrian Period. (Karen Carr for Smithsonian Institution)
Free webinar: Fossils reveal a rapid explosion of life on earth

The Earth was formed about 4.6 billion years ago. For most of its history, there was either only microbial life or no life at all.

The fossils from recognizable animal groups appeared during the Cambrian Period, which lasted from about 541-484 million years ago. During this period, there is a rapid appearance in the fossil record of nearly every major animal group for the first time. We call this rapid appearance of life the Cambrian Explosion.

A few things make the Cambrian Explosion so amazing.

The first is the speed with which it occurred. This major appearance of new and diverse animal life may have taken millions of years. While that may seem like a long time, it was really quick considering Earth’s long, 4.6-billion-year history.

The other amazing thing about the Cambrian Explosion is that the animals that appeared at this time can be connected to modern animals that are alive today. The animals from the Cambrian Period are very different from those we see today, but they have important body structures that allow us to tie them to modern animal groups.

The animals from the Cambrian Period were all marine animals; they lived in the ocean. Some of the animals were worms that lived in the seafloor. Others were mollusks, related to snails and clams today. And there were many arthropods, like trilobites, which are related to today’s crabs and lobsters. The animals that lived during the Cambrian Period are some of the earliest relatives to animals that are alive today, even humans!  

Evidence for the Cambrian Explosion comes directly from the fossil record. Scientists study fossils from this time period to understand the animals that lived half-a-billion years ago, how they may have interacted with their habitat and other animals, and even how they are connected to animals that are living today.

The animals of the Cambrian Period are both familiar and alien. Because they are so old, they give us the best opportunity for understanding the origins of modern biodiversity.

See some fossils and learn more about the Cambrian Explosion of Life with Smithsonian Paleontologist Karma Nanglu during a Smithsonian Science How webcast on March 12, 2020.

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