The ginkgo is often described as a "living fossil." But what the heck does that mean?
Charles Darwin coined the term in On the Origin of Species in reference to the platypus. Discover Online suggests that living fossils are animals (sic) that have remained relatively unchanged since they first evolved - like the platypus. The coelacanth is famously called a living fossil, though Smithsonian notes that it's more living than fossil.
Darwin suggested that these archaic forms somehow are immune to the ravages of natural selection, surviving when their compatriots go extinct due to inhabiting a protected niche without much competition. Without pressures that affect survival, there is little incentive to evolve much.
I like Darwin, and think he had great ideas. I think the term "living fossil," though, is overused and a little silly, because fossils aren't living and the experience of living long after an evolutionary starting date is hardly rare or unique. Brian Switek has a great blog posting at Wired on this very topic, entitled "Unless they're zombies, fossils don't live."
Organisms that meet the definition of living fossil are absolutely everywhere. Almost every single plant species should qualify. The various plant families originated in the antedeluvian past, some long before dinosaurs. See a moss or fern lately? A magnolia? A crazy sago palm?
The ginkgo gets star billing because it had faded out of human view for millennia, only to be revived by adventurous botanists in the 1700s and then discovered for what it was by a Japanese botanist with a microscope in 1896. Lo and behold, it was found to have exceedingly archaic sperm, characteristic of very primitive plants. Turns out that our current landscape species, Ginkgo biloba, first hit the scene about 56 million years ago. Its genus appeared 170 million years ago, in the Jurassic - dinosaur central. Its order appeared in the Permian, before the horrendous end-Permian extinction - ginkgoes made it through that bottleneck.
So the ginkgo is a special case. But plants everywhere have been around for ages and ages, way more than our paltry 200,000 years. Even the most recently evolved families, such as the Asteraceae and Fabaceae and Poaceae, are millions and millions of years old. You can look at any landscape and view snapshots from the history of life on earth. So what's a living fossil? Either all of them, or none of them.