This month in Science Roundup:

Life Cycles
Strength in Synchrony
Empathic Mice?
Genetic Clues to Lupus
Spider Web Origins
How Locusts Swarm
Keeping Cellulose on Track
The Robotic Touch
Early Fig Farming
Ancient Adornment
Sweet Plastic Precursor
Inorganic Route to Carbon Preservation
Ocean Productivity Proxy
Hyabusa at Asteroid Itokawa

This month's sponsor: Introducing Science Online Seminars

June 30, 2006 Science Online Seminar
"Pre-mRNA splicing requires proofreading of U2AF/3' splice site recognition by DEK", J. Valcarcel. Institució Catalana de Recerca i Estudis Avançats. Corresponding Author: L.M. Mendes Soares.

June 16, 2006 Science Online Seminar
"Examining Natural Selection in Humans", S.F. Schaffner, The Broad Institute of MIT and Harvard. Corresponding Author: P.C. Sabeti.

Don't miss the compelling new feature from Science : Science Online Seminars . Every other week, the editors of Science select an author of a breakthrough paper to discuss the application of the research and/or the methods and protocol in an audio/slideshow presentation. The show starts whenever and wherever you want to watch it – it's free and no registration is required. Just go to Science online from computers everywhere: http://www.sciencemag.org/onlineseminars. Science Online Seminars are produced by the Office of Publishing and Member Services.

Life Cycles
http://www.sciencemag.org/sciext/lifecycles/

What happens when researchers apply the discipline of science to the vast body of events and experiences that shape our lives? In a special section of the 30 Jun 2006 issue, Science offered a sampling of provocative insights by social scientists studying humans at different stages of the life cycle and highlighted the new tools and methodologies that are making these studies possible. News and Perspective articles explored factors that influence child development, how our political views and perceptions of happiness change with time, and the demographic effects of balancing work and family. A related Perspective in the Science of Aging Knowledge Ennvironment ( SAGE KE; http://sageke.sciencemag.org/) examined how an aging population will affect the workforce, and a collection of articles on ScienceCareers.org focused on a subset of social science careers dealing with decision, risk, and management sciences. Finally, an Editorial by N. Lane ( http://www.sciencemag.org/cgi/content/short/312/5782/1847) of the Institute for Public Policy at Rice University discussed the importance of social science research in translating technological breakthroughs into real-world solutions.

Strength in Synchrony

Neurons in the brain's thalamus play a crucial role in transmitting information from sensory stimuli, such as touch and light, to the cerebral cortex. Given how sensitive and responsive we are to inputs from the outside world, one would expect the neural connections between these brain regions to be quite strong. Not so, according to a new study in the 16 Jun 2006 Science . Bruno and Sakmann ( http://www.sciencemag.org/cgi/content/short/312/5780/1622) developed a technique for measuring the excitatory electrical activity generated in a single cortical neuron by a single thalamic neuron and showed that individually, these connections are surprisingly weak. So how does the brain respond to sensory information so effectively? It turns out that although the inputs from the thalamus are weak in isolation, they become strong by working together. Each cortical cell is the target of numerous converging thalamic inputs, which respond to sensory stimulation by generating a near-synchronous pattern of electrical discharges or spikes. These synchronized spikes are in turn very effective at exciting cortical cells. An accompanying Perspective by J.-M. Alonso ( http://www.sciencemag.org/cgi/content/short/312/5780/1604) highlighted the findings.

Empathic Mice?

Empathy is thought to be unique to higher primates and possibly to humans alone. A new study reported in the 30 Jun 2006 Science now suggests that less advanced animals can also respond to the pain of others. Langford et al. ( http://www.sciencemag.org/cgi/content/short/312/5782/1967) performed a series of experiments designed to test whether the real-time observation of pain in one mouse could affect the responses of its neighbors to painful stimuli. The researchers found that the mice exhibited enhanced pain sensitivity (shown by writhing and paw licking) when they saw a fellow cagemate experience pain, but not when the other mouse was a stranger. In addition, when familiar mice were given noxious stimuli of different intensities, their pain behavior was influenced by their cagemate's status. Does this constitute evidence of empathy? The team argues that their findings cannot be easily explained by stress, imitation, or conditioning and interpret them as evidence that mice have "emotional contagion," a primitive kind of empathy that doesn't require understanding what others are experiencing. An accompanying News story by G. Miller ( http://www.sciencemag.org/cgi/content/short/312/5782/1860b) highlighted the Report.

Genetic Clues to Lupus

Lupus is an autoimmune disease in which B cells produce antibodies directed against the patient's own nucleic acids and associated proteins. In the 16 Jun 2006 Science two studies using mouse models of the disease reveal two genes that may influence B cell responses and susceptibility to lupus. Pisitkun et al. (published online 18 May; http://www.sciencemag.org/cgi/content/short/312/5780/1669) studied a model in which a male-specific increase in the severity of the disease is associated with the duplication of a particular segment of X-chromosomal DNA that has been transposed to the Y chromosome, called the Y-linked autoimmune accelerator ( Yaa ). The researchers found that among the specific genes duplicated is the gene for the innate immune receptor TLR7, which normally discriminates between microbe and self RNA. However, increased TLR7 expression made the B cells in these mice more sensitive to TLR7 ligands and biased toward RNA-related nuclear self antigens. Meanwhile, Kumar et al. ( http://www.sciencemag.org/cgi/content/short/312/5780/1665) examined the chromosomal loci that contribute to inherited lupus in certain mouse strains. They found that a particular variant of the signaling protein encoded by the Ly108 gene makes B cells proliferate rather than die in response to signals that would normally maintain B cell tolerance, and allowed the B cells to make self-reactive antibodies. As noted in an accompanying Perspective by C. C. Goodnow ( http://www.sciencemag.org/cgi/content/short/312/5780/1606), the new studies highlight the fine line that the immune system treads between antimicrobial immunity and harmful autoimmune reactions against self.

Spider Web Origins

The orb web is an elegant, wheel-like structure woven by two groups of spiders -- deinopoids and araneoids -- to catch flying insects. Although the webs spun by each group are architecturally similar, they employ different adhesive mechanisms for ensnaring prey (dry fibrils or aqueous glue, respectively), leading some researchers to believe that the two spider lineages evolved orb weaving independently. Now, two Brevia in the 23 Jun 2006 Science offer new insights into the origins of orb webs. Garb et al. ( http://www.sciencemag.org/cgi/content/short/312/5781/1762) analyzed DNA from the silk glands of two kinds of deinopoids and found that these spiders have silk-making genes similar to those of araneoids, which suggests that the genes were acquired from a common orb-weaving ancestor. Based on fossil evidence, this ancestor probably lived at least 136 million years ago. In the second study, Peñalver et al. ( http://www.sciencemag.org/cgi/content/short/312/5781/1761), reported on the remarkable discovery of a spider web with entrapped insects within a 110-million-year-old piece of amber from Spain -- the oldest example of spider silk entrapping prey. The geometry of the silk strands suggests that it may be an orb web, which could mean that orb weaving spiders have been influencing the evolution of flying insects for millions of years. An accompanying News story by E. Stokstad ( http://www.sciencemag.org/cgi/content/short/312/5781/1730a) highlighted the findings.

How Locusts Swarm

Desert locusts threaten agricultural production in Africa , Asia , and the Middle East , and are estimated to affect the livelihood of one in ten people. Devastating swarms can cover several hundred square kilometers and contain as many as one billion individuals. Because control of flying swarms is costly and ineffective, the key to effective management of locust outbreaks is early detection of the marching juveniles (bands). In a Report in the 2 Jun 2006 Science , Buhl et al. ( http://www.sciencemag.org/cgi/content/short/312/5778/1402) investigated the mechanisms involved in the dramatic transition from marching bands to flying swarms. The researchers found that locusts undergo rapid transitions from disordered to highly aligned collective motion as their density increases. At low population density, locusts tend to have random orientations and disordered movement. The first transition occurs at intermediate density, when the insects begin to align into neighborhoods to form coherent traveling groups, but still show rapid, spontaneous changes in direction. As density increases still further, a second transition occurs in which the aligned groups acquire the high directional persistence characteristic of locust swarms in nature. The findings match predictions from models of phase transitions from disorder to order in statistical physics. As noted in an accompanying Perspective by D. Grünbaum ( http://www.sciencemag.org/cgi/content/short/312/5778/1320) these models may help inform plans for controlling locust outbreaks and more broadly aid our understanding of collective motion among social animals.

Keeping Cellulose on Track

Strong cellulose fibers called microfibrils encircle growing plant cells, lending structural support to the cells and the whole plant as it extends into the environment. In a Research Article in the 9 Jun 2006 Science , Paredez et al. ( http://www.sciencemag.org/cgi/content/short/312/5779/1491) provided the first direct evidence that microtubules tethered to the inside of the cell membrane help guide the deposition of ordered layers of these fibers by the enzyme cellulose synthase. The researchers visualized the process in living cells by expressing fluorescent versions of one cellulose synthase component and the microtubule protein, tubulin, in Arabidopsis plants. Movies show the cellulose synthases moving along trajectories defined by microtubules. The organization of the microtubules directs the organization of the growing cellulose fibrils, which may help govern the shape of the growing cell. The team also found that if a microtubule track depolymerizes, the synthases continue to move for a while; this suggests that their actual movement is powered primarily by cellulose polymerization and not by microtubules. An accompanying Perspective by C. Lloyd ( http://www.sciencemag.org/cgi/content/short/312/5779/1482) highlighted the study.

The Robotic Touch

Engineers can makes robots see and hear by equipping them with video cameras and microphones, but endowing them with a sense of touch has proven much more difficult. Simple sensors can distinguish between contact or no contact, but more sophisticated devices that can sense texture have been hampered by manufacturing challenges and lack the spatial resolution required to rival the human sense of touch. Now, a Report by Maheshwari and Saraf ( http://www.sciencemag.org/cgi/content/short/312/5779/1501) in the 9 Jun 2006 Science describes the development of a relatively simple and sturdy thin film sensor that can sense texture nearly as well as a human fingertip. Composed of alternating gold and cadmium sulfide nanoparticle layers separated by insulating polymer sheets, the sensor is only about 100 nanometers thick and responds to an applied force with light emissions that can be captured by a specialized camera, or with a change in current density. The researchers used the film to "feel" a U.S. penny, producing an image detailed enough to show the wrinkles in President Lincoln's clothing and the letters "TY" in "LIBERTY". As noted in an accompanying Perspective by R. Crowder ( http://www.sciencemag.org/cgi/content/short/312/5779/1478) and highlighted in the 9 June podcast ( http://www.sciencemag.org/about/podcast.dtl), incorporation of this sensor into robotic hands could substantially improve their dexterity for delicate applications like microsurgery.

Early Fig Farming

Scientists tracing the origins of agriculture have followed the trail of cultivated grains like wheat and barley back to about 10,500 years ago in the Near East . Now a new study reported in the 2 Jun 2006 Science suggests that fig trees could have been the first domesticated crop, preceding cereals by about a thousand years. Kislev et al. ( http://www.sciencemag.org/cgi/content/short/312/5778/1372) described the remains of figs found in several archaeological sites in the Jordan Valley as early as about 11,400 years ago. The carbonized fruits represent a variety of fig in which the fruit forms and ripens without pollination (a developmental process called parthenocarpy). Parthenocarpy results from a single rare mutation, but because these trees do not produce germinative seeds, they are reproductive "dead ends" -- unless humans interfere by replanting the tree shoots to propagate them. The abundance of parthenocarpic figs in the ancient remains implies that this was indeed the case and thus provides early evidence for fig horticulture via vegetative propagation. An accompanying News story by A. Gibbons ( http://www.sciencemag.org/cgi/content/short/312/5778/1292a) highlighted the Report.

Ancient Adornment

Art and other forms of symbolic expression have been found in many early human sites dating to about 40,000 years ago, but earlier evidence of such modern cultural behavior has been sparse. In a Report in the 23 Jun 2006 Science , Vanhaeren et al. ( http://www.sciencemag.org/cgi/content/short/312/5781/1785) presented what may be the earliest evidence yet of personal ornamentation ( see the related News story by M. Balter; http://www.sciencemag.org/cgi/content/short/312/5781/1731). The team described shell beads from Israel and Algeria dating to about 100,000 years ago -- some 25,000 years earlier than the oldest previous evidence of decorative shell beads found in Blombos Cave in South Africa . The suspected beads, which derive from marine snails, each has a distinctive type of indented perforation that occurs rarely in nature. Thus, the remoteness of the burial sites from the seashore and a comparison of the shells to natural shell collections indicate that these shells were deliberately selected (perhaps punctured) and transported by humans for symbolic use. Dr. Vanhaeren discussed the discovery in the context of the emergence of modern human culture in the 23 June podcast ( http://www.sciencemag.org/about/podcast.dtl).

Sweet Plastic Precursor

Petroleum is the key ingredient behind many commodity chemicals including plastics. But as petroleum supplies dwindle and the price of oil continues to rise, chemical companies are rekindling interest in using renewable sources like plant-based materials as alternative chemical precursors. In a Report in the 30 Jun 2006 Science , Román-Leshkov et al. ( http://www.sciencemag.org/cgi/content/short/312/5782/1933) reported a new process for turning fructose, the sugar in fruit, to a key plastic precursor called 5-hydroxymethyl furfural (HMF). The reaction system requires an aqueous phase in which catalysts convert fructose to HMF, and an organic phase that lures the HMF away from unwanted reaction byproducts. When the researchers used a combination of additives to prevent smaller side reactions, the process yielded >80% HMF when 90% of the fructose is converted. As noted in an accompanying News story by R. F. Service ( http://www.sciencemag.org/cgi/content/short/312/5782/1861), unlike previous schemes for turning sugar into HMF, the new process is efficient, easy, and a potentially cost-effective method for industrial plastic production.

Inorganic Route to Carbon Preservation

A complex web of reactions leads from primary biological products to the organic debris found in sediments and rocks. Carbon skeletons are preserved, double bonds and functional groups are lost, and saturated hydrocarbons -- the raw materials of oil -- are preserved. It has long been assumed that these reduction reactions are carried out by bacteria, but a new study in the 16 Jun 2006 Science shows otherwise. Through a series of laboratory and field studies, Hebting et al. ( published online 11 May; http://www.sciencemag.org/cgi/content/short/312/5780/1627) demonstrated that reduced carbon is preserved in rocks and oil via inorganic reactions involving hydrogen sulfide and other sulfur species, not bacterial processing. The team first used an array of spectroscopic techniques to examine the molecular structure of hydrocarbon molecules called carotenoids in lake sediments. The stereochemistry, or spatial arrangement of the atoms in these molecules, as well as the complex mixture of molecules found, indicate that they were formed through abiotic processes during the first stages if sedimentation, rather than through microbe-mediated reactions. Next, the researchers used laboratory experiments to show that sulfides are able to reduce double bonds in carotenoids and other hydrocarbons under geochemical conditions relevant to natural sediments. As noted in an accompanying Perspective by J. M. Hayes ( http://www.sciencemag.org/cgi/content/short/312/5780/1605) conventional wisdom about the pathway of carbon in nature will need to be revised.

Ocean Productivity Proxy

Phosphorus plays a key role in sustaining the biological productivity of the world's oceans, which in turn affects atmospheric carbon dioxide concentrations and climate. It also serves as a tracer of deep-ocean water masses. Understanding past productivity and its effect on global climate therefore depends on knowing how phosphorus was distributed in the sea. Unfortunately, reconstructions of ocean phosphate contents have always relied on indirect proxies that can be affected by other factors such as temperature and carbonate ion concentration, so their use is often limited by their inherent uncertainty. Now, a Report in the 23 Jun 2006 Science suggests that deep sea corals might be a reliable indicator of oceanic phosphorus concentrations. Montagna et al. ( http://www.sciencemag.org/cgi/content/short/312/5781/1788) presented evidence that the cold-water coral Desmophyllum dianthus incorporates phosphorus into its skeleton in amounts proportional to the phosphorus concentration in ambient seawater. An accompanying Perspective by E. A. Boyle ( http://www.sciencemag.org/cgi/content/short/312/5781/1758) noted that if proved robust, such a direct proxy would allow for accurate reconstructions of long-term variation in ocean phosphorus and could provide valuable insights into past ocean circulation patterns.

Hyabusa at Asteroid Itokawa
http://www.sciencemag.org/cgi/content/short/312/5778/1327

Asteroids contain detritus left over from the debris disk out of which the planets grew some 4.5 billion years ago, and as such, harbor untold clues to how our solar system formed. In a special section of the 2 Jun 2006 Science seven Reports and a Perspective detailed the bold mission of the Japanese spacecraft Hyabusa (which means falcon), the first spacecraft to visit one of the small asteroids that regularly whiz by Earth. In September 2005, Hyabusa reached asteroid Itokawa -- a tiny rocky asteroid just 500 meters across, whose elliptical orbit crosses the paths of both Earth and Mars. Infrared and x-ray spectrometer analyses show that Itokawa's composition is typical of many other asteroids. But unlike the seemingly solid asteroids previously studied, Itokawa is a rubble pile of loosely packed and porous rocks, curiously held together by the asteroid's own tenuous gravity. Its surface has both patches of rough boulder-strewn terrain and smooth "seas" of fine gravel, and the asteroid looks to be composed of two parts that resemble a small head and a larger body. After making global observations of Itokawa, Hyabusa swooped down for close-up images and sample collection. Whether any samples actually made it into the spacecraft is still unknown, but the mission has provided an exhilarating first taste of the surface of an asteroid.