The Year in Science

Sinking Chips

By Joseph D'Agnese|Saturday, January 01, 2000


Earth's human population hit 1 billion in 1804; it had jumped to 5 billion by 1987. On October 12, 1999, the 6-billionth baby, Adnan Nevic, was born at Sarajevo in Bosnia and Herzegovina. Although the population continues to grow, the birth rate is dropping almost everywhere, both because of contraceptive use and, tragically, in Africa because of deaths from aids.


Botany

Mysteries of the New Tree of Life
Believe it or not, man and mushroom now share the same branch on the tree of life. Until recently, biologists divided all living things into two kingdoms-plants and animals-but their new tree, based on DNA sequencing, starts with three big branches: bacteria, archaea, and eukaryea. The eukaryotes are divided into five smaller kingdoms: green plants, animals, fungi, red plants (mostly seaweed), and brown plants. For the last five years, 200 scientists from 12 nations have homed in on green plants, which account for one-sixth of all known species. Their revolutionary classification system, unveiled in August at the Botanical Congress in St. Louis, tells a story different from what we've ever known.

DNA analysis indicates that green plants, from the tiniest single-celled aquatic plants to the grandest redwoods, are related to one another. They all descended from a single ancestor a billion years ago: a sheet of green tissue the size of a pinhead, similar to the modern-day genus Coleochaete. Even more amazing, amborella, a little-known flowering shrub that grows only on the island of New Caledonia in the southwest Pacific, has turned out to be the closest surviving relative of the first flower, a living fossil from which all other flowers evolved. Scientists also learned that plants invaded land not from the sea, as originally thought, but from freshwater ponds, where they'd acclimated to the sometimes wet, sometimes dry environment. The wackiest finding: Fungi such as mushrooms have more in common with humans and animals than with the forest floors or the trees on which they grow.


Genetics

Get Smart
Some people dream of building a better mousetrap. Princeton neurobiologist Joseph Z. Tsien did them one better. In September he announced that he'd built a better mouse by altering a gene that affects learning and memory. A similar process of gene manipulation might conceivably be used one day to boost intelligence in humans.

The secret lies in a feature of brain cells called the nmda receptor, which Tsien likens to a cylindrical tube or window that mediates the flow of information. When the window is open, chemicals called neurotransmitters flow through easily and memory is registered and stored. But as organisms mature, the window begins to close. (This may explain why children lose their facility for learning new languages when they reach sexual maturity and why some people suffer memory loss as they age.)

Tsien noticed that the receptor worked more efficiently when teamed with the gene NR2B, so he introduced extra NR2B genes into a batch of fertilized mouse eggs. In a normal mouse, the memory window is open for just 150-thousandths of a second. In Tsien's specially engineered mice, the window opens for 250-thousandths of a second, long enough to make a remarkable difference in memory retention. When he pitted his mice against common mice, they won paws down. Ordinary mice could recognize a Lego block for 12 hours, but smart mice could remember the block for up to three days. "That's a profound enhancement," Tsien says.

Can it be done with humans? Maybe, but genetic engineering will have to make some extraordinary advances first. And some thorny ethical issues will have to be resolved. Meanwhile, Tsien promises to keep his furry little geniuses locked up in a lab, far from your larder. "Otherwise," he says, "you might need a smart cat or a smart mousetrap to catch them."


Medicine

Blood Brothers
Imagine treating Parkinson's, diabetes, or leukemia simply by injecting cells that could assume the job of their failing counterparts. How about rebuilding faulty bone, muscle, or even organs? That is the promise of stem cell research. Stem cells are precursor cells that develop into nerves, bone, cartilage, and such various tissues as brain, blood, and muscle. The most primordial-and controversial-stem cells are found in eight-day-old embryos; such cells retain the power to blossom into any of the body's myriad cell types. More developed stem cells, such as the stem cells that produce brain or blood cells, have much less flexibility.

Or so it was thought. Last January, a team of Italian and Canadian researchers reported that they had managed to transform neural stem cells into blood cells in mice. The neural stem cells were injected into mice whose bone marrow had been nearly wiped out by radiation, and five months later the mice were producing almost a full array of blood cells. The researchers believe that cues in the body-secreted perhaps by neighboring cells-can coax tissue-specific stem cells into switching careers.

So far, most stem cell research has been done in mouse models. But in September, the National Bioethics Advisory Commission, a panel of ethicists, doctors, and researchers, recommended that Congress lift the ban on using federal funds to harvest the powerful stem cells of embryos discarded after in vitro fertilization procedures. Whether or not Congress decides to lift the ban, recent mouse studies suggest that nonembryonic tissue-specific stem cells are surprisingly powerful in their own right. "When we look at animals, we think all these cells are firmly different from one another and that those differences were established very early in development," explains Ronald McKay, a stem cell researcher at nih. "But it's beginning to look as if these differences are established early in development and then maintained by a conversation that's taking place all the time. It's a transition from a gene-based view of animals, which has been dominant for 20 years, to a much more dynamic cell-based view." -Sarah Richardson


Archaeology

Lots of Mummies
A man rides his donkey down a desert road 230 miles southwest of Cairo, and the beast suddenly stumbles, its leg punching a hole in the sand. Days later, a team of archaeologists enlarges the hole the donkey so kindly began and finds a 2,000-year-old underground cemetery with as many as 10,000 mummies. The largest untouched tomb ever discovered, it has already been compared with the treasure of Tutankhamen. While some of the mummies were wrapped only in plain linen, others were elaborately painted and gilded. Some were interred in rare terra-cotta sarcophagi, and one child mummy was covered with gold. The 105 mummies excavated so far from the site near the oasis in Baharïya appear to be mostly middle-class folk who made wine from locally grown dates and grapes when Egypt was under Roman rule. The remains of their wealthy neighbors are yet to come. Even so, writes Zahi Hawass, the archaeologist in charge of work at the oasis, "I could not believe that such beautiful specimens existed. The eyes of some gazed at me as if they were alive."


Physics

Slowing Down The Speed of Light
The speed of light in a vacuum is more than 670 million miles per hour. The speed of light in glass is about two-thirds of that. But the speed of light in a cloud of sodium cooled to a few billionths of a degree above absolute zero is only 38 mph, a remarkable discovery reported by Harvard physicist Lene Vestergaard Hau last February. Horses run faster-though perhaps not under the conditions that prevail in her lab at the Rowland Institute for Science in Cambridge, Massachusetts.

Hau starts with a magnetic trap inside a vacuum chamber, which she uses to create a strange kind of matter called a Bose-Einstein condensate-a cloud of atoms (sodium in this case) reduced to the same quantum state of near-zero energy so that they become profoundly cold and still. Next she and her fellow researchers send a pulse of light from a "probe" laser into one end of this tenth-of-a-millimeter-long, cigar-shaped cloud. "Then we just wait and measure the pulse when it comes out," she says.

If that were all there was to her setup, the pulse would never come out. The sodium cloud would simply absorb all the photons. Hau's solution to this problem is to illuminate the cloud from the side with a second laser-the "coupling" laser. Its slightly different photon energy primes the sodium atoms for a quantum leap different from the one suggested by the probe laser-and that confuses the atoms. The upshot is that the whole pulse is slowed dramatically.

Hau sees applications for her scheme in optical communications and computing. "It's like a transistor-it's really an optical switch," she says. Meanwhile, Hau continues to improve on her record. In October she slowed a pulse to half a meter per second, a shade over one mph. Her goal is a centimeter per second: light as slow as a turtle. -Robert Kunzig

Paleontology
Bernard Buigues led an expedition to a remote area of Siberia to excavate an adult male mammoth carcass, believed to be 23,000 years old. Buigues marked the site with the tusks, which were found separated from the mammoth's body. The mammoth was carefully preserved in a 23-ton block of ice and airlifted by helicopter on October 17 to a permafrost tunnel, where it will be maintained at 12 to 14 degrees Fahrenheit.

Plans to retrieve DNA and clone the creature are afoot.


Zoology

Cultured Chimps
Those poor chimps, we think. We all started as equals, but somehow we got the smarts and they ended up in zoos or cheesy film shorts. But information released last June suggests the joke's on us. Nine researchers-Jane Goodall among them-asserted in a landmark study that, based on an analysis of 151 years of data from seven long-term projects, chimps have culture.

Biologists define culture as a collection of behavior patterns that can be transmitted only by watching, knowing, and living with other members of a society. While songbirds learn songs from other songbirds and, in some cases, even warble dialects different from same-species birds living in other places, this behavior has never been accepted as true culture by biologists, because it is only a single tradition. Chimps, on the other hand, display many behaviors that, taken together, constitute a fascinating, if primitive, culture passed down from one generation to the next. Somewhere in the past, a chimp developed a way to groom itself, to forage for food, or to make itself comfortable, which others in its group emulated. Researchers identified 39 such traits, all subject to community taste. In some locales, chimps knock their knuckles to get others to listen to them; in others, they snap tree branches or stomp on a shrub.

This is little different from humans, some of whom eat corn typewriter-style while others slice off kernels with a knife. Freud argued that culture was man's bulwark against his animal nature, the proof that man was different in kind than the animals. This study suggests we owe our simian cousins a greater debt than we've acknowledged.

A Good Year for Peregrines
SINCE the Endangered Species Act was passed in 1973, 1,200 species have been listed by the U.S. Fish and Wildlife and National Marine Fisheries Services as endangered or threatened. Only 29 species have been delisted in these 27 years, seven of those because they became extinct. The good news in 1999 was that the peregrine falcon and Lloyd's hedgehog cactus were once again flourishing sufficiently to leave the list. The year's many and painful additions to the federal register included:

ANIMALS
Bull trout Threatened
Chinook, chum, sockeye,and steelhead salmon(selected locations) Threatened or endangere
Flatwoods salamander Threatened
Lake Erie water snake Threatened
Sacramento splittail fish Threatened
Sierra Nevada bighorn sheep Endangered
PLANTS
Catesbea melancarpa Endangered
Howell's spectacular thelypod Threatened
Ione plants (3 varieties) Endangered
Johnson's sea grass Threatened
Maui Nui plants (10 species) Endangered



Chemistry

Brief Encounters
Lab-made elements are the priceless gnats of chemistry. They blaze into being, twinkle merrily for microseconds, and die. With the exception of plutonium (number 94 in the periodic table), elements heavier than uranium (number 92) are so unstable that they can be cooked up only in nuclear reactors or particle accelerators. Last January, scientists at the Joint Institute for Nuclear Research in Dubna, Russia, created element 114, which lasted for 30 seconds-a lifetime in the subatomic world. In June, 116 and 118 were born, courtesy of scientists at the Lawrence Livermore National Laboratory in California. Lifetimes of 116 and 118 were as much as one one-thousandth of a second and three ten-thousandths of a second, respectively, long enough to suggest that we may have reached the island of stability predicted since the 1970s to occur at about atomic weight 114, where new elements last longer than fractions of a nanosecond.


Space

Earth to Mars: We're Coming
Back in the 1970s, Mars coyly teased us with her dimples, but now we're onto her: We can count them, date them, and, of course, theorize about how they came to be. Last year, major studies revealed a world whose hide is scarred by at least 3 billion years of activity, a world once teeming with spouting volcanoes, grinding crustal plates, sandy dunes, and deeply carved valleys. One study illuminated the role of volcanoes in Mars' development: They spewed water and gases that fed its atmosphere and terrain. That water, said another team, may have helped carve mysterious pinkish canyons. Other scientists focused on the odd pattern of magnetic bands in Martian rock, possible evidence that tectonic plates were once propelled forward by volcanic rifts. But for all this new knowledge, a big question remains: How could a past so dynamic, maybe even wet and warm, so . . . so . . . Earth-like, vanish into the quiet, frosty desert we see today?

Hopes to plumb these meteorological mysteries firsthand were rudely dashed in September, when Mars Climate Orbiter, a $125 million, 1,387-pound robotic weather satellite, vanished just as it prepared to circle the planet. nasa's embarrassment went off the chart when the cause was revealed: The craft's builder, Lockheed Martin, had specified measurements of thrust in the English unit of pounds, while nasa had used metric newtons in its calculations. Says project scientist Richard Zurek, "I would compare it to a death in the family. It feels very final. And there are all those things you wanted to do." But the work continues. Orbiter's launch partner, Mars Polar Lander, is designed to use a backhoe to sample dirt at the Martian south pole. Companion probes that were blasted into the red soil will test density and check for traces of water. This seemingly endless probing of soil is no mere geologic preoccupation. Beyond solving the mystery of where the water went, scientists are simply being pragmatic. "We might want to go there someday," says Zurek. "And it's not really cost-effective to bring a planetful of water with us."

Eileen Collins, the first female shuttle commander, piloted Columbia and deployed the Chandra X-ray Observatory successfully this past July, despite a fuel leak and a short circuit that knocked out key computers during launch. Today 29 of the 121 astronauts and three of the 42 shuttle pilots are women.





Boston Museum of Science's Web site: www.mos.org.


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