Such a groundbreaking finding requires confirmation from other experiments to be truly believed, physicists say. Nevertheless, the result has won praise from many leaders in the field. “There’s a chance it could be wrong, but I think it’s highly probable that the results stand up,” says Alan Guth of the Massachusetts Institute of Technology, who first predicted inflation in 1980. “I think they’ve done an incredibly good job of analysis.” The BICEP2 detectors found a surprisingly strong signal of B-mode polarization, giving them enough data to surpass the “5-sigma” statistical significance threshold for a true discovery. In fact, the researchers were so startled to see such a blaring signal in the data that they held off on publishing it for more than a year, looking for all possible alternative explanations for the pattern they found. Finally, when BICEP2’s successor at the same location, the Keck Array, came online and began showing the same result, the scientists felt confident. “That played a major role in convincing us this is something real,” Kuo says.

But how do the different flower forms serve the common end of intercrossing? Darwin believed that they all served—in different ways—to enlist flying insects to transport pollen from one plant to another. These different “contrivances” had evolved, Darwin believed, under virtually the same environmental circumstances, e.g., the same range of available insects. Sometimes one part of the flower had been modified to entice insects in the vicinity, by mimicry or by scent; sometimes another part had been modified to do the same job. Once the insects had arrived, the pollen had to be attached. Some flowers were so constructed as to catapult pollen at the visiting insects; some catapult the insects against the pollen; some simply induced the visitors to travel past and brush-up against the pollen. Etc., etc. Thus cross-pollination was accomplished in very different ways, the different outcomes being due in large measure—Darwin argued—to natural selection acting on chance differences in variation among different lineages.

Darwin might have explained the different outcomes mainly in terms of differences in environmental conditions—e.g., differences in the insects available for conscription as pollinators. Thus, he might have presumed that different lineages of orchids experience the same variations, in the same order, and then he might have argued that different variations are selected in different lineages depending on which pollinators are in the vicinity. But he did not. His emphasis was on chance differences in variation among lineages.

This emphasis might be obscured by Darwin’s famous analysis of the Madagascar star orchid, Angraecum sesquipedale, which has an extraordinarily long nectary—up to a foot in length. Darwin reasoned that such a long nectary must serve to attract an insect with an equally long proboscis, although no such insect was known at the time to exist in Madagascar. The hypothetical scenario was initially dismissed as fantasy. Darwin took satisfaction in Fritz Müller’s discovery, reported in the second edition of Orchids, of a moth in southern Brazil (unfortunately, halfway around the world from Madagascar), with an eleven-inch proboscis. Darwin didn’t live long enough to enjoy the satisfaction of Walter Rothschild and Karl Jordan’s 1903 description of the long-tongued and appropriately located (in Madagascar) “Morgan’s sphinx moth,” subsequently named Xanthopan Morgani praedicta. But Darwinians since then have treasured the successful prediction.

Again, the main point of Orchids was to attribute differences in floral morphology to natural selection acting on whatever differences chance to arise.