URBANA — Carl Woese thought about things a lot.
And when a question or problem drew his attention, he would ponder it not for weeks or months, but for years.
"It's not even clear that the atmosphere of science these days is supportive of that perspective, but he was a master of it," said Gary Olsen, a collaborator with Mr. Woese and a fellow microbiologist at the University of Illinois.
"Carl was single-minded in his pursuit of the big tree" of life, added Norman Pace, a distinguished professor of molecular, cellular and developmental biology at the University of Colorado at Boulder and a Woese colleague for decades.
Mr. Woese, 84, who discovered a third domain of life, died at his home Sunday in Urbana.
Schmoozing at parties or pursuing a cult of personality — that was not Carl Woese, colleagues said. A scientist's scientist, he was a visionary thinker who valued greatly the science and the work.
In 2003, when Mr. Woese was awarded the prestigious Crafoord Prize by the Royal Swedish Academy of Sciences, he told The News-Gazette that the real importance of his discovery was the door it opened to better understanding the roots and process of evolution. He quoted a Chinese proverb that says when a wise man points out the moon, only a fool looks at the finger.
"The work is the moon, and I am the finger," he said.
Prior to Mr. Woese, it was thought there were two branches in the tree of life: prokaryotes (bacteria) and eukaryotes (such as plants and animals).
He claimed certain microbes, now called archaea, were as distinct from bacteria as plants and animals are. Thus the new, third branch of the tree of life.
"It changed how we view the tree of life ... and his work has had huge implications we are even now just starting to come to terms with," said Gene Robinson, UI entomologist and director of the university's Institute for Genomic Biology.
Mr. Woese was an early supporter of the institute and its "discovery-oriented science really fit his intense creativity," said Robinson, who called him a "patron saint of the institute." He became a founding member of its biocomplexity theme.
Robinson called him an inspirational teacher who challenged students. A stern taskmaster, Mr. Woese was also intellectually playful and encouraged students to think for themselves, he said.
James Davis, a postdoctoral fellow at the IGB, worked with Mr. Woese at the institute and took courses with him while studying at the UI.
During a course on microbial evolution, Davis said Mr. Woese spent time explaining the basis of his discoveries but also trying to impress upon students how to think properly about problems, to question statements, terminology and more.
If you don't understand what you described, how can you solve the next problem, Davis said he learned from Mr. Woese.
"This is the key to understanding why he was so good as a scientist," Davis said. "He was very good at teasing things apart. He brought a great deal of clarity to his field."
Born July 15, 1928, in Syracuse, N.Y., Mr. Woese earned bachelor's degrees in math and physics from Amherst College in 1950. He went on to earn a Ph.D. in biophysics from Yale University in 1953.
For two years he studied medicine at the University of Rochester, and worked for five years as a postdoctoral researcher in biophysics at Yale and as a biophysicist at the General Electric Research Laboratory in Schenectady, N.Y.
In 1964, he became a professor of microbiology at the University of Illinois.
Pace was a graduate student at the UI when Mr. Woese arrived. They would interact a lot while Pace was on campus and kept in touch throughout the decades.
"I think he did more for biology than (Charles) Darwin did. Darwin — he was a sociological phenomenon. ... Woese, he put a quantitative face on evolution," when he started comparing gene sequences from different organisms in the 1970s, Pace said.
Added Olsen: "He had a remarkably good idea for not falling for dogma."
Some theories may be seductive or sound like a good story, and they're easy to fall for, Olsen said.
Mr. Woese "had a particularly great ability at recognizing what do we actually know and what are people filling in and making up as we go, how much of science is a 'just so' story," he said.
That was a reference to Rudyard Kipling's book, "Just So Stories," which features fantastical takes on, for example, how camels got their humps and leopards got their spots.
With a "burning desire to understand evolutionary relationships between the microbes," Mr. Woese's re- search would help give insights into how life evolved, Robinson said.
In his work, Mr. Woese zeroed in on the ribosome. Instead of classifying organisms by observing their physical traits, he analyzed evolutionary relationships by comparing genetic sequences.
The method used by Mr. Woese is now reverberating in 21st-century biology in the form of metagenomics, Robinson said. That is, the idea of going out to a particular environment, the backyard or the deepest sea, and then finding out what kind of microbial life is living there.
Scientists are now in the early stages of describing all these microscopic worlds, to show how one microbial community in the body is different from another part, how a healthy body's microbial community is different from a diseased one, he said.
"The whole area has profound implications for all biology, medicine, evolution and environmental biology," Robinson said.
Mr. Woese received a MacArthur Foundation grant in 1984, was elected to the National Academy of Sciences in 1988 and was awarded the Leeuwenhoek Medal, microbiology's premier honor, in 1992. He received a National Medal of Science in 2000.
"Carl was the greatest evolutionary biologist of the 20th century — a true revolutionary," UI physics Professor Nigel Goldenfeld, a colleague and friend, said in a statement. "Beginning as an outsider, he turned a field that was primarily subjective into an experimental science, with wide-ranging and practical implications for microbiology, ecology and even medicine that are still being worked out.
"The largely untold story of the intellectual struggle he endured, and his years of hard, painstaking work have been a model of how scientific discoveries get made and a source of inspiration to all those whose lives he directly touched, be they scientists, educators, students or lay people," Goldenfeld said.
When asked in 2002 why anybody but biologists would care where cells came from billions of years ago, Mr. Woese told The News-Gazette, "Where'd you come from? This is a forever, perennial question: 'Where do I come from?' I'm just trying to construct a part of that road."
Referring to an article published earlier this year in "Nature Reviews Microbiology," which outlined reasons for Mr. Woese to receive a Nobel Prize, "the entire yield on his original work hadn't been seen yet," Davis said.
Mr. Woese is survived by his wife, Gabriella; and their children, Gabriella and Robert, both of whom live in Atlanta; and a sister, Donna Daniels of New York.
A memorial service will be held at the University of Illinois in late January.