SAMPLINGS 



A/as/can glacier is on the move. 



Icequake 



A global network of seismometers con- 

 stantly monitors the Earth's rumbles and 

 grumbles. Three years ago Goran Ekstrom, 

 a geophysicist at Harvard University, no- 

 ticed some unusual, low-frequency seismic 

 waves, which looked nothing like the sig- 

 nals of moving tectonic plates. The strange 



waves, he discovered, orig- 

 inated in Alaska, Antarc- 

 tica, and Greenland, where 

 massive glaciers were 

 lurching downslope, then 

 stopping abruptly, shaking 

 f 1 " the earth below. 



Once they identified 

 if the source, Ekstrom and 

 • ' • ' two colleagues combed 



, , through seismographic 



records from 1993 through 

 2005, and picked 136 of 

 i ,«i the best-recorded "glacial 

 * earthquakes" originating 

 ■ - at the edge of the Green- 

 . land ice sheet. The investi- 



gators found that those 

 j '■ quakes took place most 



frequently in the late sum- 

 mer months. Presumably, 

 ~ that's when the most melt- 

 water trickles down to 

 the bases of the glaciers, 

 reducing the friction be- 

 tween ice and ground and easing the 

 glaciers along. And glacial earthquakes are 

 on the rise. In 2005 there were twice as 

 many quakes in Greenland as in any year 

 before 2002. Glacial meltwater seems to 

 be flowing freely these days, yet another 

 sign of the warming climate. {Science 31 1 : 

 1756-8, 2006) 



— Stephan Reebs 



Europe's First Fashionistas 



The first anatomically modern humans to 

 colonize Europe forged what archaeologists 

 now call the Aurignacian culture, which per- 

 sisted throughout Europe between 37,000 

 and 28,000 years ago. Over such a long time 

 and wide area, it seems plausible that the 

 Aurignacians spawned various subcul- 

 tures and languages. 

 Until now, though, 



Early European bijoux 



regional differences 

 among Aurignacian 

 artifacts have been 

 hard to identify. 



Recently, how- 

 ever, the archaeologists Marian Vanhaeren 

 of the University of Paris X and Francesco 

 d'Errico of the University of Bordeaux I, both 

 in France, have distinguished three broad 

 geographical regions in the distribution of 

 the Aurignacians' ornamental beads and 

 pendants. The ornaments were usually shells, 

 teeth, or bones, perforated or grooved to 

 accommodate a cord. In parts of present-day 

 Belgium and Germany, perforated teeth and 

 tear- or disk-shaped ivory beads were more 

 fashionable than elsewhere. In parts of Aus- 

 tria, southeastern France, Greece, and Italy, 

 shells tended to be de rigueur. The mix of 

 ornaments from Spain and from southern 

 and western France is intermediate between 



Gender Bias 



Hypoxia, or oxygen scarcity, is accelerating 

 across vast reaches of the world's waters. 

 The cause is often pollution, and by now as 

 many as 400,000 square miles of ocean are 

 permanently hypoxic. In such areas, fish pop- 

 ulations plummet. Some fish species simply 

 drop dead from too little oxygen. But a new 

 study suggests that low oxygen levels may 

 also alter the sex ratios among fish popula- 

 tions, thereby compromising their survival. 



Eva H. H. Shang and Rudolf S. S. Wu, 

 both ecotoxicologists at the City University 

 of Hong Kong, and a colleague compared 

 zebra fish reared in tanks under hypoxic 

 conditions with a control group raised in 

 normally oxygenated water. After four 

 months, the investigators discovered that 

 many more males than females developed 

 in the hypoxic tanks — 74 percent of the 

 population compared to 62 percent in 

 "normoxic" tanks. They blame the imbal- 

 ance on an altered ratio of two sex hor- 

 mones at a stage in development when the 

 fishes' gender is determined. Female fish 

 reared in hypoxic tanks produced more 

 testosterone and less estradiol than did fish 

 reared in normoxic tanks. The cause, Shang 

 and Wu found, was changes in the expres- 

 sion of genes that manufacture the sex hor- 

 mones. The changes in hormone levels 

 likely inhibit the development of female re- 

 productive organs and other sexual traits 

 and encourage male organs and sexual 

 traits to develop instead. Fish with girl 

 genes, it seems, grow up with boy bodies. 



Shang and Wu suspect that even if fully 

 female fish do manage to survive in hy- 

 poxic environments, they may produce 

 fewer, poorer-quality eggs than normal. Be- 

 cause a fish population's reproductive suc- 

 cess is limited by the number and fecundity 

 of its females, Shang and Wu worry that 

 hypoxia may be even more harmful to the 

 world's fishes than previously thought. {En- 

 vironmental Science & Technology, doi:10. 

 1 02 1 /es522579, 2006) —Rebecca Kessler 



the other two regions. Because the same 

 raw materials were available everywhere, 

 Vanhaeren and d'Errico argue that such fash- 

 ion trends reflect cultural — and perhaps even 

 linguistic — differences, and that the first 

 Europeans were a diverse bunch. {Journal of 

 Archaeological Science, in press, 2006) 



—S.R. 



NATURAL HISTORY June 2006 



