American Scientist

This roundup summarizes some notable recent items about scientific research, selected from news reports compiled in Sigma Xi’s free electronic newsletters.

The Oldest Leper

Anthropologists have diagnosed leprosy in 4,000-year-old bones, making them the oldest known direct evidence of the disease. The remains, found in northwest India, bear symptoms such as pitting and erosion of the nose and cheek bones. Previously, the oldest evidence of leprosy was a 2,200-year-old Egyptian skeleton. The newly described bones support the controversial idea that Indian Vedic texts refer to leprosy, and also jibe with historical records that the disease appeared in Europe when Alexander the Great returned from India.

Robbins, G., et al. Ancient skeletal evidence for leprosy in India (2000 B.C.). PLoS ONE 4(5):e5669 (May 27)

Laughing for Ten Million Years

Infant apes squirm, pant and grunt when tickled. A new acoustic analysis confirms what researchers have long suspected: Ape and human laughter share a common origin. Researchers built a phylogenetic tree based on properties of laughter in infant apes and humans—like voicing versus panting, or making sounds on inhalation versus exhalation. The sound tree was a perfect match to the evolutionary tree of apes and humans, suggesting that all our giggles are homologous. Humans and apes diverged 10 to 16 million years ago, so laughter has been in the family at least that long.

Davila Ross, M., et al. Reconstructing the Evolution of Laughter in Great Apes and Humans. Current Biology 19:1106–1111 (July 14)

A Healed Heart

At 11 months old, British infant Hannah Clark’s heart was weak, enlarged and failing. Doctors saved her life by grafting a second heart onto her own. But over several years, anti-rejection drugs allowed a virus-induced cancer to invade the child’s body, and reducing the drug dose caused the donated heart to fail. In a medical first, doctors removed the second heart ten and a half years after they installed it—and Clark’s own heart now powers healthy circulation. The organ’s gradual comeback over several years provides rare evidence for the heart’s resilience, and doctors hope that understanding Clark’s case will guide long-term treatment in other patients.

Tsang, V., et al. Late donor cardiectomy after paediatric heterotopic cardiac transplantation. The Lancet (published online July 13)

Bats Know Their Buddies’ Voices

Bats often hunt in groups, and researchers have wondered how they coordinate these social outings. It may help that they can tell each other apart by the sounds of their echolocation calls. Researchers trained five greater mouse-eared bats (Myotis myotis) to choose recordings of one bat over another. A mealworm snack rewarded correct choices. After a few weeks of training, bats continued to select the correct voices about 80 percent of the time. Based on a computer model that duplicated the bats’ errors, the researchers think the bats remember an “average” call for each acquaintance. Then they recognize individuals by comparing their voices to the memorized templates.

Yovel, Y., et al. The voice of bats: How greater mouse-eared bats recognize individuals based on their echolocation calls. PLoS Computational Biology 5:e1000400 (June 5)

The Holocene Caribou Hunt

Caribou herds tend to move along linear landscape features. Modern Arctic hunters exploit this preference by building drive lanes, lines of large stones that steer caribou toward an ambush. Archaeologists think prehistoric Americans were doing the same thing 7,500 to 10,000 years ago on land that now lies beneath Lake Huron. Using sonar and underwater robots, researchers located what could be an ancient drive lane, cairns and a hunters’ blind made of boulders. If divers confirm the find with unequivocally manmade artifacts, the site will add to the scarce relics of early Holocene cultures around the Great Lakes.

O’Shea, J. M., and G. R. Meadows. Evidence for early hunters beneath the Great Lakes. Proceedings of the National Academy of Sciences 106:10120–10123 (June 23)

The Case of the Missing Frog Legs

Amphibian decline is a high-profile environmental issue, and deformed frogs often symbolize the crisis. But amphibians with missing limbs may be victims of dragonflies, not pollution. Immature dragonflies, or naiads, are wingless aquatic predators. In laboratory experiments, 18 out of 20 dragonfly naiads (Sympetrum sp.) dismembered hundreds of toad tadpoles (Bufo bufo,) eating their legs and tails but leaving the injured amphibians to mature. These toads, as well frog tadpoles with experimentally amputated legs, often grew up with deformities resembling those in nature. But environmental deterioration could still be a factor, if it alters interactions between tadpoles and dragonflies.

Ballengée, B., and S. K. Sessions. Explanation for missing limbs in deformed amphibians. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution (published online June 8)

Early Supernovae Found

Some giant stars—those 50 to 100 times the mass of the sun—can emit particularly bright ultraviolet light when they collapse and explode in supernovae. Researchers took advantage of this radiance to detect 11 billion-year-old supernovae, the oldest yet found, and just two billion years younger than the universe itself. Because even the brightest flashes are hard to spot so far away, researchers compiled multiple images of the same area of sky, taken over several months. Bright patches emerged, representing the combined light emitted over the duration of each supernova. The results give an unusual glimpse of cosmic dynamics in the young universe.

Cooke, J., et al. Type IIn supernovae at redshift z ≈ 2 from archival data. Nature 460:237–239 (July 9)