When Yale University paleontologist Nicholas Longrich began studying a prehistoric bird called Archaeopteryx, he noticed something unexpected.
For starters, the bird had small feathers on its hind legs. When he began doing a feather-by-feather reconstruction of its wings, working from a fossil in Germany, he found it didn’t look like a modern bird at all. Instead of the single layer of feathers that give modern birds their dextrous flight abilities, the fossil appeared to have layers of feathers stacked on top of each other, almost like two-ply tissues.
“I realized you couldn’t really get from what the fossils showed to the way people were drawing it,” Longrich said.
His painstaking study of the Archaeopteryx fossil suggested to Longrich that this Jurassic-era bird had a primitive wing, and may not have been very good at flying. But instead of publishing his observation, he decided to sit on it. He wasn’t sure that his colleagues would be convinced; it might have been something strange about the way the specimen he was studying was fossilized.
A few years later, a scientist working down the hall from him, Jakob Vinther, began studying a fossil of a feathered dinosaur that had been recently discovered in China, called Anchiornis huxleyi. Vinther was not a bird specialist — in fact, Longrich said, Vinther normally studied fossils of ancient squid, octopi, and worms. But that also meant Vinther didn’t have the same preconceptions, and when he looked at the fossil he also saw wings with multiple layers of feathers.
The scientists have now published their work, describing the primitive wings of both Archaeopteryx and Anchiornis, in the journal Current Biology. Longrich says that the wing probably functioned, but not as well as in modern birds. Archaeopteryx probably was “OK at getting around from point A to point B, level flight or flapping flight,” Longrich said, but not so good at flying at low speeds or hovering. The feathered dinosaur, on the other hand, was probably more of a glider, he said.
DNA material demonstrates unexploited versatility
Engineers have found a new and unexpected use for the code of life — as a commonplace building material that can be used to fashion precise 3-D structures, ranging from miniature smiley faces to cubes.
Most people think of DNA as the master blueprint that is carried in every cell, spelling out the essential traits of organisms. DNA is the “building block of life” only in the metaphorical sense. But scientists at the Wyss Institute for Biologically Inspired Engineering at Harvard University saw in the material an unexploited versatility, if it were to be used as a real brick. They described Thursday in the journal Science an array of molecular Legos that could one day provide a useful scaffold for building tiny electronic circuits and drug-delivery devices.
To show just how much control they had over structures made of DNA, the team of researchers built a demonstration set of 100 figures. Those ranged from practical engineering feats, such as joining together two structures with a narrow connection, to the whimsical — the alphabet, or a heart.
When Hendrik Dietz, who leads the Laboratory for Biomolecular Nanotechnology at Technische Universität München in Germany, received a copy of the paper from a colleague at Harvard a few weeks ago, he was full of enthusiasm for the work. It represents a new level of control over building precisely tailored objects at the tiniest scales, he wrote in an e-mail. But Dietz said he also had an almost instantaneous emotional response.
“The 3-D thing is so awesome,” he wrote to the person. “I almost got tears in my eyes because of the joy. I love the Lego figures. When looking at this, one cannot help but submit to the power of DNA.”
Peng Yin, a core faculty member of the Wyss Institute who led the research, said it was helpful for the researchers to think of the DNA as Lego bricks rather than as molecules. The code of DNA involves four letters — C, G, T, and A — which abide by precise pairing rules: “A” matches up with “T,” and “C” with “G.” To build the structures, researchers started with short strands of DNA, each carrying eight-letter fragments that acted like the prongs on a Lego block. Each eight-letter fragment was like a Lego prong that would only fit one other predetermined Lego.
But unlike a kit that keeps kids busy for hours, these DNA structures required little assembly, once the structures had been designed, Yin said.
“You just add some water and salt and increase the temperature to 90 degrees and let it cool down gradually over three days,’’ Yin said. “In one test tube, there are billions of copies of these individual objects, but they all look the same.”
George Church, Yin’s colleague and Wyss Institute collaborator, said the work would be helpful in any application in which precision was important, and demonstrates an alternate role that DNA can play, as a structural material. “It’s a terrific scaffolding, which is not at all what nature intended it to be,” he said.
UMass scientist finds evidence in excrement
Three years ago, geoscientist Robert D’Anjou climbed into an inflatable raft and navigated to the deepest spot in Lake Liland in northern Norway. He and collaborators dropped a coring device about 45 feet down and began to drill, in what would turn out to be a quixotic scientific search for the ancient remains of human excrement.
D’Anjou, a graduate student at the University of Massachusetts Amherst, did not start out with scatological interests. He was interested in reconstructing historical climate records by studying layers of sediment.
But he realized that many of the indirect markers that scientists used to look for past climate changes were intricately linked to human influence. Scientists often search for pollen, for example, but changes in plant life can be a sign not only of climate change, but agriculture. Similarly, erosion could reflect changes caused by climate fluctuations — droughts that killed plants that held soil in place, for example — but could also be caused by the introduction of livestock or changing land use.
So he began examining the sediments in detail, and found that coprostanols — molecules produced in human guts as people digest cholesterol — could be used in combination with other more commonly used molecular remains to understand interactions between humans and their environments. The results, published last Monday in the Proceedings of the National Academy of Sciences, suggest a possible new approach to understanding the relationship between prehistoric humans and their environment. Still, D’Anjou has kept a sense of humor about the whole project.
“You can’t take yourself too seriously. I studied Viking poop,” D’Anjou said. “It’s hilarious, but at the same time you’ve got to look at it kind of pragmatically. . . . People have been recording their stories throughout history in the most unlikely of places — in their poop.”