Some 65 million years ago, a riot of flowering plants burst upon the world. Where did they come from? A remarkably well-preserved fossil from China suggests that the forebears of flowering plants may have been aquatic, weedy herbs.
The question of flowering plants' origin has perplexed evolutionary biologists ever since Charles Darwin called it an "abominable mystery." Most paleobotanists have long believed that flowering plants, or angiosperms, arose from woody plants resembling the magnolia tree. That made sense, because the closest known relatives of angiosperms--the conifers and other so-called gymnosperms--are all woody.
The newfound 125-million-year-old plant may change all that. A team of paleontologists led by Ge Sun of Jilin University in Changchun, China, and David Dilcher of the Florida Museum of Natural History describe the find in the 3 May issue of Science. The plant has clear flowerlike traits. The female reproductive structure, called the carpel, is closed with seeds inside. The male organs, known as anthers, resemble modern ones and lie below the female parts, a classic hallmark of flowers. But Archaefructus would raise a florist's eyebrows: It has no sepals or petals, and strangest of all, its stamens come in pairs rather than singly. Based on this constellation of features, the team claims Archaefructus is the closest known relative to the first flowers.
Archaefructus supports the idea that early angiosperms were herbs. Herbs grow faster and reproduce younger than other seed plants do, and that could have given them an edge over slower-growing competitors. What's more, the find suggests that early flowering plants lived in water. Nearby fish fossils in the same type of rock, the plant's delicate stems, and bulbous structures that may have served as floats all hint that Archaefructus grew in lakes.
Although many other experts are smitten by Archaefructus, they say they won't be swept off their feet until they've had a closer look at the characters used to establish its evolutionary position. "Everything depends on whether [Archaefructus] is correctly positioned in the tree," says Michael Donoghue of Yale University.