SCIENCE
Notebook

Monday, June 26, 2006

Accessories Go Primitive

Archaeologists searching through artifacts unearthed long ago have found what they believe are three ornamental marine snail-shell beads that are about 100,000 years old, the oldest known evidence of personal decoration.

Archaeologist Marian Vanhaeren of University College London said she and Francesco d'Errico of France's Institute of Prehistory and Quaternary Geology found the shells while searching for evidence to bolster earlier claims that beads found in Blombos cave in South Africa were 75,000 years old. Vanhaeren said she and d'Errico worked in Blombos.

Until Blombos, Vanhaeren said in a telephone interview, "there was the prevailing view that humans became culturally modern only when they invaded Europe 40,000 years ago." The Blombos findings have been hotly disputed.

Reporting last week in the journal Science, the two researchers said they had found two perforated snail shells that had been excavated in the 1930s at Es-Skhul, in what is now Israel, and another dug from Oued Djebbana, in Algeria, in the 1940s.

Vanhaeren said all three shells were found with the remains of anatomically modern humans, and both sites were far from shore, indicating that whoever carried them inland had done so deliberately, with the intention of stringing them in an ornament.

Vanhaeren said the shells were from the same genus of marine gastropod as the Blombos shells and had the same sort of holes punched in them. Such holes are almost impossible to find in nature today among such shells, she said.

The results are certain to remain controversial, because there is no evidence of any human ornamental or artistic design between the beads and bone carvings from Europe beginning 40,000 years ago and those from Blombos, 35,000 years earlier and thousands of miles away.

-- Guy Gugliotta

Trees Elected and Reelected, Too

It may not be as closely watched as the biennial congressional elections. But every two years in the United States, hundreds of trees are elected or reelected to the National Register of Big Trees -- a carefully judged contest that brings a modicum of fame to the single biggest representative of almost every American species of tree.

The 870 winners, announced last week by American Forests, a District-based group that has coordinated the registry since 1940, includes 119 newly elected winners. Candidates are typically nominated by local people who believe that a tree they know of may be the biggest of its kind. Winners are verified by state coordinators using a system that takes into account height, circumference at shoulder height and total crown spread.

The General Sherman giant sequoia in California continues its reign as the largest tree of all. It is one of three that have held their titles since 1940. The General is 274 feet tall with an 85-foot circumference and a 107-foot crown spread.

The smallest largest member of its species is a 16-foot-tall corkwood tree in Florida.

A total of 119 new champs and co-champs were named this year, including an American elm in Fountain Creek, Va., that was declared to be equally as large as the incumbent elm champ in Tennessee. All told, Virginia has 54 national champion trees, including the largest white oak, white mulberry and red buckeye.

Maryland boasts the biggest box elder and southern crab apple trees and a co-champion poison sumac (which is tied with a Virginia specimen), among others.

The District has a single national champion tree: a huge common jujube, 61 feet tall with a 93-foot circumference, shading a nice patch of the U.S. Capitol grounds.

-- Rick Weiss

Webcasting's Ancient Origins

Two very different kinds of spiders make the same kind of orb spider web -- the ingenious wheel-shaped contraption that has been trapping flies, beetles and wasps through the ages. Biologists once assumed this was an example of convergent evolution, the independent emergence of the same useful traits in different species.

New research published last week in Science, however, suggests that the complex architecture involved in spider webs may have been devised by a single common ancestor that dates back about 136 million years.

DNA analysis by Jessica Garb and her colleagues at the University of California at Riverside showed that spiders known as Deinpoidea , such as the net-casting spiders, and Araneoidea, which include the golden silk spiders, both inherited certain key proteins from this common ancestor.

Both kinds of spiders build the radial structure of webs in similar ways, but they use different substances for the silky nets that trap flying prey. The nets have to be enormously strong to absorb the kinetic forces of a hurtling insect: Deinopoids use dry silks to create a mesh and to trap prey using electrostatic forces. Araneoids use a gluey silk that traps prey by being sticky.

Araneoid silks have been extensively studied. Garb and her fellow researchers genetically analyzed deinopoid silks and showed that they shared a common genetic lineage with araneoid silks.

-- Shankar Vedantam