Ancient plants mirror modern trees.
Herbal medicine's favorite tree, the Gingko, is a living fossil. Newly found specimens that grew more than a hundred million years ago are remarkably similar to present-day plants1.
Extracts of the Gingko or maidenhair tree, a distant relative of the conifer, are believed to improve concentration and stave off dementia. Some specimens in Chinese monastery gardens are over three thousand years old. Others, such as those in Utrecht and Kew Gardens, are approaching three hundred. Wild specimens are extinct.
Previous fossils revealed that Ginkgo species have remained unchanged for the past 51 million years, and that similar trees were alive and well 170 million years ago, during the Jurassic period. But what happened between the two dates was unknown. The new finds, from the 121-million-year-old Yixian rock formation in northeast China, provide a much-needed missing link between ancient and more modern plants.
Their perfectly preserved leaves and reproductive organs show that the Gingko's "morphology has changed little for over 100 million years", say Zhiyan Zhou and Shaolin Zeng of the Chinese National Institute of Geology and Palaeontology, Nanjing, who analysed the relics.
There are subtle differences between living Gingko species and Jurassic examples. The leaves of the Jurassic plants are divided into several lobes - similar to those of the chestnut tree. The new fossils show that 50 million years later, the lobes had joined up into the small fans of today's specimens.
The way that seeds are formed has also changed. Today's Gingko makes a few seeds, only one of which reaches full maturity, on a single stalk. Jurassic trees have sprays of stalks, each sporting a single seed. The new fossils are a halfway house, with multiple seeds on a single stalk.
There is now little doubt that today's Gingko is a direct descendent of forebears that provided food for the dinosaurs.
Zhou, Z. & Zheng, S. The missing link in Gingko evolution. Nature, 423, 821 - 822, (2003).