To Charles Darwin, the sudden appearance of flowers in the geologic record was “an abominable mystery,” one that was a clear exception to his proposal that the history of life had been one of slow, gradual change.  The phrase, “an abominable mystery,” still echoes today among those who are pursuing the question of the origin and evolution of flowers.


Flowering plants, that is angiosperms, account for most of the diversity of living plants and include all agricultural crops.  The oldest confirmed fossil flowers are no older than 130 million years old placing them well within the Cretaceous Period, the period of the dinosaurs.*  Among the oldest fossil flowers are those that were found in a sequence of rocks known as the Potomac Group that stretches from Richmond, Virginia, to Baltimore, Maryland.  Though these early flowers were small—most measure less than a tenth of an inch in size—they clearly had the reproductive structures of modern flowers, such as carpels and stamens.


Then over a period of a few tens of millions of years—comparable to the length of time of the Cambrian Explosion when most of the different animal forms (the phyla) developed—there was a burst in the diversity of flowers.  The trigger for the burst is still debated.  Perhaps it was the simultaneous diversification of insects that became the pollinators for the flowers.



* Though the age of the oldest confirmed fossil flowers is 130 million years, there is genetic evidence that angiosperms may have originated as early as 190 million years ago.