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Are we past our ‘extinct by’ date?
SOME SAY the world will end in fire, some say in ice, wrote Robert Frost. But whatever is to be our fate, it is now overdue.
After analysing the eradication of millions of ancient species, scientists have found that a mass extinction is due any moment now. Their research has shown that every 62 million years — plus or minus 3m years — creatures are wiped from the planet’s surface in massive numbers.
And given that the last great extinction occurred 65m years ago, when dinosaurs and thousands of other creatures abruptly disappeared, the study suggests humanity faces a fairly pressing danger. Even worse, scientists have no idea about its source.
“There is no doubting the existence of this cycle of mass extinctions every 62m years. It is very, very clear from analysis of fossil records,” said Professor James Kirchner, of the University of California, Berkeley. “Unfortunately, we are all completely baffled about the cause.”
The report, published in the current issue of Nature, was carried out by Professor Richard Muller and Robert Rohde also from the Berkeley campus. They studied the disappearances of thousands of different marine species, whose fossils are better preserved than terrestrial species, over the past 500m years.
Their results were completely unexpected. It was known that mass extinctions have occurred in the past. During the Permian extinction, 250m years ago, more than 70 per cent of all species were wiped out, for example. But most research suggested that these were linked to asteroid collisions and other random events. But Muller and Rohde found that, far from being unpredictable, mass extinctions occur every 62m years, a pattern that is ‘striking and compelling’, according to Kirchner.
But what is responsible? Here, researchers ran into problems. They considered the passage of the solar system through gas clouds that permeate the galaxy. These clouds could trigger climatic mayhem. However, there is no known mechanism to explain why the passage might occur only every 62m years. — Dawn/The Guardian News Service (c) The Observer
The ‘X’ factor
It was slow to reveal its secrets, but the X chromosome has now bared it all. Researchers recently said they had determined with 99.99 per cent accuracy the genetic code of the X chromosome, which lay at the core of human femaleness.
The newly completed picture of the X chromosome — one of the last orders of business for the human genome project — falls far short of explaining all the mysteries of what makes a woman. But by determining the exact order of virtually all 155 million “letters” of code on the X — the counterpart to the male Y chromosome — scientists have confirmed how sex evolved and are much closer to explaining some of the differences between men and women.
The X chromosome’s unveiling also brings into focus the molecular underpinnings of hundreds of genetic diseases, far more than have been discovered on any other human chromosome. And it appears to have revealed a long-sought role for much of the body’s “junk DNA,” which is especially prevalent on the X, and whose lack of apparent function has long baffled scientists.
Perhaps most tantalizing, the new work sheds light on one of the most astonishing acts of self-effacement in all of biology: the permanent shutting down of half of the X chromosomes in every cell of a girl’s body — an effort to match the activity of the single X that men inherit with their Y.
“It’s more evidence that it’s not so much what you’ve got as how you use it,” said Mark Ross of the Wellcome Trust Sanger Institute in Cambridge, England, who led the gargantuan sequencing effort involving 282 scientists at 21 institutions in six countries, including the United States.
The new findings are described in a pair of scientific reports published in the journal Nature and clarify preliminary findings of the past few years. — Dawn/LAT-WP News Service (c) Washington Post
Man or mouse?
What happens when you cross a human and a mouse? Sounds like the beginning of a bad joke but, in fact, it’s a serious experiment recently carried out by a team headed by a distinguished molecular biologist, Irving Weissman, at Stanford University.
Scientists injected human brain cells into mouse foetuses, creating a strain of mice that were approximately 1 per cent human. Weissman is considering a follow-up that would produce mice whose brains are 100 per cent human.
What if the mice escaped the lab and began to proliferate? What might be the ecological consequences of mice who think like human beings, let loose in nature? Weissman says that he would keep a tight rein on the mice, and if they showed any signs of humanness he would kill them. Hardly reassuring.
Experiments like the one that produced a partially humanized mouse stretch the limits of human tinkering with nature to the realm of the pathological. The new research field at the cutting edge of the biotech revolution is called chimeric experimentation. Researchers around the world are combining human and animal cells and creating chimeric creatures that are part-human, part-animal.
The first chimeric experiment occurred many years ago when scientists in Edinburgh fused a sheep and goat embryo — two unrelated animal species that are incapable of mating and producing a hybrid offspring. The resulting creature, called a geep, was born with the head of a goat and the body of a sheep.
Now, scientists have their sights trained on breaking the final taboo in the natural world — crossing humans and animals to create new human-animal hybrids. Already, aside from the humanized mouse, scientists have created pigs with human blood and sheep with livers and hearts that are mostly human. — Dawn/The Guardian News Service
GM crops harm environment?
The largest study ever undertaken on genetically modified (GM) crops has concluded they can harm wildlife, setting the stage for a fight in Britain over whether to allow farmers to cultivate bio-engineered crops.
The last trial in a four-year study, published earlier this week, compared GM winter-sown rapeseed to its conventional non-GM equivalent, and found that in GM fields there were fewer seeds, bees and butterflies. The rapeseed, like many other GM crops designed by agro-industrial corporations, is designed to resist herbicide so that farmers can use a broad spectrum of powerful weedkillers. In the GM crop's fields there were also fewer broad-leaved weeds — considered important because they feed insects — even though there were some grass weeds and soil insects remaining.
The results were the last of four major farm-scale trials overseen by the British government. — Sci-tech World Report
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