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Assembling the Tree of Life - 2002-06-08

Scientist from around the world have come together at a three-day conference at New York City's American Museum of Natural History to help the public understand the pattern of relationships that link all species on Earth.

The "Tree of Life" is much like a family tree, except that its branches are not adorned with the names and birth dates of a few dozen people. Instead it bears all of the millions of species that exist on earth today, and those that have existed throughout the nearly four billion years of earth's history. It answers the questions: How are we humans related to animals, plants, and bacteria? And, How are they related to each other?

The Tree of Life was just a seedling as recently as 10 years ago. Then, explains Dr. Michael Novacek of the Museum of Natural History, science made remarkable advances in the field of genome sequencing. "Ten years ago we didn't have much of this information. It's only been in the last five years that we've been able to sequence so many genes and with so much technology that we've actually uncovered a lot of relationships between organisms that we weren't aware of before," he says.

The discovery of these relationships is leading to marked growth of the Tree of Life, according to Dr. Novacek's colleague, Harvard Professor Edward O. Wilson. Dr. Wilson says the Tree marks the beginning of a new era in biology. "It will be the basis for all kinds of new endeavors of a synthetic sort: comparing species, behaviors, developing patterns, meaning of different parts of the biological organizations and so on. I think there will be an exponential explosion of knowledge in biology. The next few decades are certain to be a new age," he says.

Dr. Wilson says that, currently, more than 90 percent of the Earth's species remain unknown to science. In the next 25 years, however, he thinks a "complete census of all species" - a fully-grown Tree of Life - is attainable.

But the Tree has practical applications that are already in use by science.

Dr. David Hillis studies HIV/AIDS. He says the Tree of Life presents a clear picture of the relationship between viruses, how they circulate in the human population, and how they got into the population in the first place. "It's even possible to trace individual infections. It's been used in criminal investigations when there have been purposeful transmissions, as in the case of the physician convicted of purposefully infecting his mistress with HIV from one of his patients who was HIV positive. These kinds of questions can be answered by looking at the relationships between the individual viruses," he says.

Dr. Hillis also pointed out that the Tree was instrumental in tracing the anthrax infections that struck almost 18 people in the United States late last year, killing five.

By all accounts, scientists have only begun to reap the rich rewards the Tree of Life has to offer. But, according to Dr. Novacek of the Museum, the Tree of Life has already spawned at least one headline-grabbing revelation. "One thing this conference tells you is that dinosaurs didn't go extinct, because one lineage of dinosaurs exists today: birds. That's an insight that comes from studying the Tree of Life. It tells us that birds are not only related to dinosaurs, they are dinosaurs," he says.

But if the birds twittering in the trees surrounding the American Museum of Natural History are not enough for dinosaur fans, they can find what the Museum calls the "largest and most important" collection of dinosaur fossils in the world, inside.