Not So Rapid Eye Movement
The bizarre metamorphosis that occurs in halibut and other flatfish had even Charles Darwin floundering for an explanation. At birth, these fish have one eye on each side of the skull, but as adults, both eyes reside on the same side. Certainly, for fish that spend their lives along the sea bottom, having both eyes topside confers a survival advantage. But there seemed to be no evolutionary reason to start down the gradual path toward such lopsidedness—any intermediate steps would not seem to be especially helpful. So some biologists theorized that the fish evolved from a single, sudden mutation.
That does not seem to be the case: Matt Friedman of the Field Museum in Chicago reports finding some missing links. He investigated two roughly 50-million-year-old primitive flatfish fossils hidden in museums in Europe for more than a century. These adult specimens possessed somewhat asymmetrical skulls that nonetheless kept eyes on opposite sides of the head. Even incomplete lopsidedness may have given the carnivorous bottom dwellers a better view of the world above than no asymmetry at all, Friedman conjectures. Eye the study in the July 10 Nature. —Charles Q. Choi
As parents have long known, children in day care centers and schools readily spread respiratory diseases among one another. Chimpanzee communities seem to suffer in a similar way: playdates drive the dissemination of respiratory infections among the primates, according to a new study.
Scientists led by Hjalmar Kuehl and Peter Walsh of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, examined two chimpanzee groups in Taï National Park in Ivory Coast. Infants were more likely to die from a respiratory disease the more they played together—typically during the peak fruit season, when chimps congregate. Between the ages of two and three, chimps spend up to 18 percent of their day engaged in close physical contact with their peers. This period represents the peak of their social interaction and serves to connect all members of their community.
Once playful chimpanzees precipitated an outbreak, infants of all ages succumbed to disease. Affected mothers quickly entered into estrus, ultimately perpetuating the three-year cycle of infant population boom and bust. Coupled with poaching, climate change and predation, infant mortality from infectious disease is taking
a toll on the area’s chimps, says Kuehl, whose research findings appear in the June 18 PLoS ONE. These days few infants reach adulthood, he states, with “only four out of 10 surviving to the age of five.” —Barbara Juncosa
Another Gene for Alzheimer’s
A newly identified genetic mutation increases the risk for the most common form of Alzheimer’s disease—the second major gene to be linked to the neurodegenerative disorder. The mutation occurs in the so-called CALHM1 gene, which controls calcium concentrations in nerve cells. Researchers observed that mutant CALHM1 led to increased accumulation of amyloid beta plaques, the sticky protein clumps characteristic of the disease. In the U.S.
Alzheimer’s affects one in 20 adults aged 65 to 74; carrying one defective copy of CALHM1 escalates the risk to one in 14 (and to one in 10 for those carrying two defective copies). The mutation also leads to an earlier age of onset. Reporting in the June 27 Cell, lead author Philippe Marambaud of the Feinstein Institute for Medical Research in Manhasset, N.Y., states that the CALHM1 gene—along with the first Alzheimer’s gene, APOE, discovered 15 years ago—will be important in screening for the disease. —Barbara Juncosa
The New Stone Age
Kidney stones will become more prevalent in the 21st century as the world warms up, according to Tom H. Brikowski of the University of Texas at Dallas and his colleagues. A crystallization of minerals dissolved in urine, a stone can form with the help of fluid loss. Such dehydration is more common in hotter conditions; the incidence in the southeastern U.S. is 50 percent greater than in the northwestern region of the country, for instance, and some U.S. soldiers shipped to desert conditions developed stones just 90 days after deployment. Factoring in the expected rise in mean temperature in the U.S.—upward of two to five degrees Celsius this century—the researchers figure that the nation will see 1.6 million to 2.2 million more kidney stone cases by 2050. This 7 to 10 percent increase could exact $1.3 billion in medical costs. The findings are crystallized in the July 15 Proceedings of the National Academy of Sciences USA. —Philip Yam
Who Will Die?
Researchers have built a computer system that can predict which death-row inmates are most likely to be executed. It consists of 18 computer processors that analyzed data on about 1,000 death-row prisoners, including their sex, age, race, schooling and whether they were ultimately executed or spared. Then the researchers fed it similar information about 300 more prisoners, leaving out whether they had lived or died. The system, using logic it had developed from the first set of data, correctly predicted the outcome for 92 percent of those cases. It found that death-row inmates with the highest chance of being executed are those with the lowest levels of education; neither the severity of the crime nor race could reliably predict a prisoner’s fate. The findings, which the researchers hope will lead to a fairer appeals process, appear in the Spring 2008 International Journal of Law and Information Technology. —Larry Greenemeier
Global warming is leaving trees behind. Some two thirds of forest species in six French mountain ranges have moved at least 18.5 meters higher on the mountainsides per decade during the 20th century. Previous research has demonstrated that plants at the highest elevations on mountains and in the polar regions have shifted to adjust to global warming. The latest result marks the first confirmation that entire ecosystems in lower, more temperate regions are moving as well. The study is in the June 27 Science. —David Biello
LOCATION INFLUENCES VOTERS
The voting location may tip the balance on some election issues. Researchers examined the 2000 Arizona general election that included a proposed tax increase to support school initiatives. After controlling for political preferences and zip codes, the researchers found that voters casting ballots at schools tended to support the measure (63.6 percent in favor) more so than those at nonschool booths (56.3 percent). A follow-up experiment revealed that voters could be subconsciously “primed” with images of lockers and classrooms to vote for a hypothetical tax for school spending. The July 1 Proceedings of the National Academy of Sciences USA contains the findings. —Philip Yam
Researchers have long suspected that a massive asteroid caused Mars’s “hemispheric dichotomy”: its crust thins from 50 to 20 kilometers over a south-north span covering 42 percent of its surface. Using gravity data and other measurements, scientists have discovered the hidden outline of the impact—in particular, an elliptical mark spanning 10,600 by 8,500 kilometers. Simulations suggest that the asteroid measured 1,600 to 2,700 kilometers wide, moved at about six to 10 kilometers per second, and struck at an angle of 30 to 60 degrees with the ground. —JR Minkel