Biology will dominate the 21st century much in the way that the computer chip was the most influential technology of the previous half century. So at least many biologists believe, and events of 2000 lent substance to this view.

The genome of the Drosophila fruitfly was sequenced in March, giving biologists the full parts list of a favorite laboratory organism. At a White House ceremony in June, the two rival teams racing to sequence the human genome declared a truce and jointly announced the essential completion of their task. And a powerful new technology based on stem cells started to prove its promise as a possible way of rejuvenating the body's diseased or aging tissues.

Despite these advances, which promise to underpin a new era of medical progress, some serious problems grew worse. AIDS, largely contained in the United States and Europe, continues to devastate many countries in Africa. Cases of mad cow disease continue to accumulate in Britain, with the future extent of this incipient epidemic still impossible to predict.

Here are the top 10 science stories of 2000:

1. The linguist Joseph Greenberg reported that languages spoken from one end of the Eurasian continent to the other, from Portuguese to Japanese, belong to a single ancient superfamily of languages. Though Greenberg's thesis is rejected by many historical linguists, it fits with the finding by population geneticists that the Eurasian continent was inhabited by a small number of people who emigrated from the ancestral human homeland in Africa.

2. Many fundamental discoveries in biology have been made in the Drosophila fruitfly, which has been a standard laboratory organism for more than 90 years. J. Craig Venter and colleagues at the Celera Corporation sequenced the entire DNA of the Drosophila genome, giving fruitfly biologists a powerful tool to help accelerate their research. Another important genome sequenced this year was that of the first plant, a standard laboratory organism known as Aridopsis. The Aridopsis genome is expected to help plant biologists studying important crops.

3. Two rival teams racing to sequence the human genome decided at the last minute that they had more to gain from declaring joint victory than from making separate announcements. The human genome sequence is expected to revolutionize medicine since almost every disease has a genetic component.

4. AIDS continues to cut a relentless swathe of suffering and curtailed lifespan through many countries of Africa. In the worst affected countries two thirds of today's 15 year olds will eventually contract AIDS and die, unless the epidemic is immediately reined in.

6. After 4 flat years, cases of mad cow disease resumed their increase in Britain, dashing hopes that the incipient epidemic had peaked. An untreatable infection that turns the brain to mush, mad cow disease is contracted by eating diseased beef.

7. The first inhabitants arrived at the International Space Station and a few weeks later a second space shuttle delivered solar panels with which to power it.

8. Physicists at the European particle accelerator believed they had captured the first experimental evidence for the existence of the Higgs boson, a predicted subatomic particle which occupies a central place in the leading theory of matter.

9. Stem cells, the special cells used by the body to repair and maintain its own tissues, are coming to the fore as a possible medical treatment for many degenerative diseases of aging. Among many advances in understanding stem cells, biologists showed how they could be used to repair damage to the brains of rats, enabling paralyzed animals to move again.

The concept of regenerative medicine suggests that a new kind of medicine, based on stem cells and cell signaling factors, could be developed. Its goal would be not just to patch up damaged tissues but to replace and rejuvenate them.

10. Archeologists and population geneticists are on the verge of a grand synthesis that will document the history of the past 50,000 years, at least in terms of the migrations by which humans left Africa and populated the rest of the world. Drawing on new data derived by analyzing mutations in the Y chromosome, geneticists have reconstructed the migrations that first brought people into Europe between 45,000 and 20,000 years ago.

Referenced Articles
• What We All Spoke When the World Was Young (February 1, 2000 NYTimes)
• On Road to Human Genome, a Milestone in the Fruit Fly (March 24, 2000 NYTimes)
• First Complete Plant Genetic Sequence Is Determined (December 14, 2000 NYTimes)
• Genetic Code of Human Life Is Cracked by Scientists (June 27, 2000 NYTimes)
• Deaths Tied to Mad Cow Disease on the Rise (July 25, 2000 NYTimes)
• On a Particle's Trail, Physicists Seek Time (November 4, 2000 NYTimes)
• In Early Experiments, Cells Repair Damaged Brains (November 7, 2000 NYTimes)
• Teaching the Body to Heal Itself (November 7, 2000 NYTimes)
• Scientists Rough Out Humanity's 50,000-Year-Old Story (November 14, 2000 NYTimes)