In 2005, North Carolina State University paleontologist Mary Schweitzer made headlines when she reported finding soft tissue in the femur of a T. rex. Until then, researchers believed that such tissue would have degraded eons ago. Now Schweitzer’s team has sequenced 68-million-year-old collagen proteins from the T. rex, the oldest sequences ever reported. They were similar to chicken collagen, adding to the mountain of evidence that dinosaurs are most closely related to birds. “Now we can compare these organisms at the sequence level, which is very powerful because you don’t have to rely on what types of bones you’re finding or how intact the fossil was,” says Harvard University mass spectrometrist John Asara, who led the sequencing project.
Schweitzer’s finding follows on the heels of another study led by Harvard biologist Chris Organ, who managed to estimate how much DNA dinosaurs had, despite the lack of any surviving genetic material. Organ suspected that he could estimate the size of a dinosaur’s genome indirectly by taking advantage of data from living animals. In existing vertebrates, genome size correlates very closely with bone cell size, so Organ used the size of dinosaur bone cells to predict how much genetic material the extinct animals possessed. According to Organ’s analysis, the largest creatures ever to walk the earth had staggeringly small genomes, most comparable in size to . . . modern birds. Previously, biologists assumed that birds’ compact genomes emerged around the time they took to the skies, but now it seems that millions of years ago their ancestors had similarly puny genomes. “The genomic structure of birds ends up being—like feathers and parental care—not avian but dinosaurian in origin,” Organ says.
