American Scientist

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

Must Find Flower . . . Cough, Cough

It should come as no surprise to anyone who enjoys the scent of flowers that bees and other pollinators do too—or rather that they use floral scents to locate these sources of food. But it is startling, and indeed disturbing, to learn that air pollution may be making the process harder for insects than it was in preindustrial times. A new study reveals that the hydrocarbons that flowers give off are destroyed by atmospheric pollutants such as low-level ozone, which markedly reduces the distance from which a pollinator can detect a flower—from kilometers to less than 200 meters.

McFrederick, Q. S., J. C. Kathilankal and J. D. Fuentes. Air pollution modifies floral scent trails. Atmospheric Environment 42:2336–2348 (March)

Early Whales Got the Bends

Divers suffer decompression sickness—the "bends"—when gas within the body goes into solution at depth and then forms small bubbles in the blood when the person returns to the surface. These gas emboli can damage capillaries, and bone supplied by these vessels can die, a condition called osteonecrosis. Professional scuba divers often develop osteonecrosis, and even pearl divers sometimes suffer from it. But for reasons that are not entirely clear, deep-diving mammals such as whales appear to be largely immune. A study of fossil cetaceans (the group that includes whales, dolphins and porpoises) reveals that some very early forms of these creatures may well have suffered from diving-induced osteonecrosis, suggesting that they evolved mechanisms to overcome decompression illness relatively quickly.

Beatty, B. L., and B. M. Rothschild. Decompression syndrome and the evolution of deep diving physiology in the Cetacea. Naturwissenschaften (published online April 30)

There’s Gold in Them Thar Mountains

Ancient objects made of hammered native gold have been unearthed from an unlikely spot. Fabricated by people who were just settling into a sedentary life in the Lake Titicaca basin (present-day Peru), these artifacts were placed in a burial site nearly 4,000 years ago. The group of low-level food producers that lived there at the time may have been the very first metalworkers in the Andes.

Aldenderfer, M., N. M. Craig, R. J. Speakman and R. Popelka-Filcoff. Four-thousand-year-old gold artifacts from the Lake Titicaca basin, Peru. Proceedings of the National Academy of Sciences of the U.S.A. 105:5002–5005 (published online March 31)

The Skinny on Fat

The pounds that so many people struggle to shed are contained in specialized fat cells, or adipocytes. A new study that makes use of trace amounts of carbon-14 generated during nuclear-bomb tests reveals that these cells grow and shrink in size (as people put on weight or lose it) but hardly change in number—at least for people who become obese relatively early in life. Adipose cells do not, however, live that long; their constancy in an individual appears to be a result of some mechanism that tightly regulates their numbers. This observation perhaps explains why dieters are prone to regaining the weight they lose and may suggest a new avenue for combating obesity: reducing the overall number of adipocytes a person has by modifying this still-murky regulatory mechanism.

Spalding, K. L., et al. Dynamics of fat cell turnover in humans. Nature (published online May 4)

Taking It All In—the Hard Way

Sometime in the dim past, creatures gained the ability to leave the sea and occupy land. One important adaptation for that transition was the development of lungs. Biologists have, however, known of rare instances where evolution has worked in reverse: Certain lungless salamanders, for example, are known to have evolved from ancestors that had lungs. Now a team working in Borneo has discovered another such anomaly: a lungless frog. The species, Barbourula kalimantanensis, is able to respire just by taking in oxygen through the skin.

Bickford, D., D. Iskandar and A. Barlian. A lungless frog discovered on Borneo. Current Biology 18:R374 (May 6)

The Long, Hot Desertification

Environmental scientists have long been aware that the Sahara was once a relatively lush place, home to hippos and other large fauna. Details of the area’s transition to a hyper-arid desert have, however, been sparse. But a new study sheds light on the history of this great climate transition using finely laminated sediments preserved in one of the few permanent water bodies of the region: Lake Yoa of northern Chad. Analysis of these sediments reveals a 300-year-long transition from a freshwater habitat to a distinctly saline lake, a change that took place about 4,000 years ago. Drying of the nearby land apparently took longer, with a gradual reduction in tropical vegetation followed by a slow loss of grass cover, leading to the modern desert.

Kröpelin, S., et al. Climate-driven ecosystem succession in the Sahara: the past 6000 years. Science 320:765–768 (May 9)

By the Sea . . . By the Beautiful Sea

Many scholars have been puzzled by the Monte Verde archaeological site in southern Chile. Evidence recovered there suggests that people were present some 14,600 years ago—not long after the very first immigrants to the New World crossed over the Bering land bridge between Alaska and Siberia. Yet little has been found showing the presence of people between these northern and southern extremes. How did the first migrants get to Monte Verde? This new works suggests that some of them at least stayed close to the shoreline, taking advantage of coastal resources. The evidence consists of seaweed and a stone artifact that contains the remains of seaweed on its worked edge.

Dillehay, T. D., et al. Monte Verde: seaweed, food, medicine, and the peopling of South America. Science 320:784–786 (May 9)