CALIFORNIA: Among the theories to explain the disappearance of mammoths and the Clovis stone tool tradition in North America around 13,000 years ago is a comet or meteor impact that triggered a continent-wide inferno. "Carbonaceous spherules" formed by intense heat are supposedly evidence for the theory, but new research has concluded that such microscopic particles had a more prosaic origin—as fossilized bits of fungus or insect droppings exposed to run-of-the-mill wildfires. (Courtesy Andrew Scott, Royal Holloway, University of London)

VIRGINIA: In addition to being tasty with a little lemon, oysters provide a window into the challenges faced by the settlers at Jamestown, North America's first permanent English colony. By studying the oxygen isotopes in shells found in a well, scientists determined that the bivalves were harvested from saltier water caused by a severe drought in the years before 1612. At the time, falling water levels expanded oyster habitat closer to the colony, providing more of the shellfish to eat, though malnutrition still claimed the lives of many colonists. (Courtesy Preservation Virginia)

MEXICO: At the highland Maya city of Palenque, marine fossils - including Carcharodon megalodon shark teeth and stingray spines from 63 million years ago - were used as funerary offerings. The ancient Maya believed that their lands emerged from the sea and associated the underworld with water. The fossils may have had special significance 100 miles from the ocean - a connection with both the origin of humanity and the watery destiny that awaited after death. (Courtesy INAH)

ENGLAND: The remains of 40 infants, from a group of 97 excavated from a Roman villa in 1912, were recently rediscovered in a museum collection, presenting archaeologists with a grim puzzle. Tests show that all the infants died shortly after birth. One sordid theory is that the third-century villa had been a brothel; another is that they were the children of the owners and workforce of the villa and surrounding communities, and had accumulated over more than a century. Researchers plan to look more closely for causes of death and to see if they can extract DNA. (Courtesy 360 Production)

MESOAMERICA: Add a mastery of rubber-making processes to the list of achievements of the ancient Maya, Aztecs, and Olmec. It's known that the Mesoamerican cultures could make the versatile material from the sap of the rubber tree, but according to new experiments, they had the tools to make rubber bend to their will—a tough version for sandals, a bouncy kind for balls, and a resilient type for bands. They could do all of this by cooking various proportions of the sap with juice from morning glory vines. (Kimbell Art Museum, Fort Worth, Texas/Art Resource)

ARMENIA: A layer of sheep dung in a cave helped protect the world's oldest known shoe, made from a single piece of leather, tied with laces, and filled with grass that probably helped it keep its shape. It was buried in a pot—as part of some ritual (the cave also holds pot-burials of children)—5,500 years ago, several hundred years before Ötzi and his famous footwear. The same shoe design would go on to be used across Europe for thousands of years. (Courtesy Ron Pinhasi, University College Cork, Boris Gasparian, Institute of Archaeology and Enthography, National Academy of Sciences, Armenia)

CHINA: The secret ingredient that gives ancient Chinese mortar its legendary strength is sticky rice. An analysis of samples from the Ming Dynasty (A.D. 1368-1644) city wall in Nanjing showed why the rice is such an effective additive to lime mortars. Amylopectin, the rice compund in the mortar, provides mechanical strength and stability, and inhibits the growth of calcium carbonate crystals, resulting in a more compact and resilient binding material. Chinese scientists re-created the mortar and determined that it is ideal for restoring ancient structures. (Wikimedia Commons)

RUSSIA: During the construction of a new road outside Vladivostok, crews stumbled upon a mass grave containing 495 skeletons: 3.5 tons of bones in all. According to local reports, almost all the skulls have gunshot wounds, and volunteer archaeologists found clothes and money that help date the grave to Stalin's purges in the 1930s.

EGYPT: Two 2,000-year-old crocodile mummies from the Phoebe A. Hearst Museum at Berkeley were given CT scans. One, which has baby crocs attached to its back, still has its internal organs, including a full stomach containing an ancient metal fishhook. The other has an intact skull beneath its mask, but is otherwise composed of a jumble of bone fragments, including the jaw of another croc. This suggests that it was a votive offering, and not an embodiment of the crocodile god Sobek. (Collection of the Phoebe A. Hearst Museum of Anthropology, UC Berkeley)

ETHIOPIA: "Lucy," the diminutive Australopithecus afarensis found in 1974, is no longer alone. "Kadanuumuu" (meaning "big man" in the Afar language), a much larger example of the early homind species, was recently found in the same region. At nearly 5.5 feet tall, he would have towered over her by 2 feet, and at 3.6 million years old, he predates her by about 400,000 years. His longer legs prove that their species was fully bipedal - a conclusion that had been in doubt because Lucy's legs were so short - and walked much like modern humans. (Yohannes Haile-Selassie, Liz Russell, Cleveland Museum of Natural History. Used with permission from the Proceedings of the National Academy of Sciences)