By HENRY FOUNTAIN
Published: August 25, 1998
Black Truffles: Viva Variety
THAT culinary delicacy, the black truffle, may be relatively rare and expensive these days, but pity the poor cave man: the supply appears to have all but shriveled up around 10,000 years ago.
That is the hypothesis of a trio of researchers (from France, naturally) who studied black truffles with an eye to understanding why they vary in flavor and aroma. In a brief article in Nature, they report that the fungi, which are found among tree roots, show almost no genetic variation across the species. This contrasts sharply with burgundy and summer truffles, which vary greatly.
Genetic sameness can often be linked to a population bottleneck, an event that kills most of a species, leaving a relative handful of specimens (and a correspondingly small gene pool) to carry on.
Unlike the other two varieties, the black truffle ripens in winter, and can be killed by a cold snap. The researchers theorize that the truffle's population bottleneck came in the last Ice Age -- that cold snap of epochal proportions, which ended about 100 centuries ago -- when European forests were greatly reduced.
They conclude that differences in the perfume and taste of black truffles are probably due to environmental conditions and suggest further research to identify the specific influences. Well, somebody has to do it.
While shedding tears for the truffleless cave men of Europe, save some sympathy for the mountain dwellers of pre-Columbian South America. Some of them, it turns out, may have had stomach ulcers.
Dr. Pelayo Correa, a pathologist at Louisiana State University, detected antigens for Helicobacter pylori, the bacteria at the root of peptic ulcers, in stool samples from Andean mummies. Dr. Correa used a new test designed to detect infection in living people, but it proved effective in remains that were up to 1,800 years old. His findings are the earliest evidence of H. pylori infection in humans.
Current thinking that there is not enough mass in the universe to stop it from expanding forever has received support from the seemingly paradoxical discovery of a huge mass in space: a cluster of thousands of galaxies containing trillions of stars.
The cluster, found by Megan Donahue and others at the Space Telescope Science Institute in Baltimore, is eight billion light-years from earth. In addition to its great mass, it is incredibly hot -- the gas between galaxies is calculated to be 300 million degrees Fahrenheit. The presence of such a massive cluster so far away, and thus so far back in time, suggests that the cluster did most of its accumulating when the universe was relatively young, and has since slowed its growth.
This finding runs counter to the theory of a dense universe that could eventually collapse upon itself. If there was a lot of mass around to be accumulated, clusters of galaxies would grow continuously, and the most massive ones would have been growing longest. It would be highly unlikely to find one so early in time.
But a cluster that has grown relatively quickly and then slowed supports the opposite idea, that the universe is relatively lightweight, without the critical mass that would allow clusters to grow steadily or prevent its own eternal expansion.
Flawed Mercury Measure
Mercury, the element, not the planet, is one of the world's great environmental poisons. It accumulates in the food chain, starting in plankton and building up through ever larger sea creatures to wind up in humans, where it is toxic to the nervous system. The amount of mercury from industrial processes and the burning of coal and solid waste has long been a concern.
Now American and French researchers have shown that one important barometer of mercury pollution, measurements of the amount of the metal found in the Greenland ice cap in the 1970's, was too high. Where tests of snow samples two decades ago found mercury concentrations as high as 800 parts per trillion, the new studies, of samples from 1949 to 1989, found concentrations below 2 parts per trillion. Apparently the older testing methods contaminated the samples.
Drawing (Nurit Karlin)