The 100 Most Influential Scientists of All Time (39 page)

From 1951 Turing had been working on what is now known as artificial life. He wrote “The Chemical Basis of Morphogenesis,” which described some of his research on the development of pattern and form in living organisms, and he used the Ferranti Mark I computer to model chemical mechanisms by which genes could control the development of anatomical structure in plants and animals. In the midst of this groundbreaking work, Turing was discovered dead in his bed, poisoned by cyanide. A homemade apparatus for silver-plating teaspoons, which included a tank of cyanide, was found in the room next to his bedroom. The official verdict was suicide, but no motive was ever discovered.

(b. March 25, 1914, Cresco, Iowa, U.S.)

A
merican agricultural scientist and plant pathologist Norman Ernest Borlaug helped to lay the groundwork of the so-called Green Revolution, the agricultural technological advance that promised to alleviate world hunger. For his achievements he was awarded the Nobel Prize for Peace in 1970.

Borlaug studied plant biology and forestry at the University of Minnesota and earned a Ph.D. in plant pathology there in 1941. From 1944 to 1960 he served as research scientist at the Rockefeller Foundation's Cooperative Mexican Agricultural Program in Mexico. Borlaug's work was founded on earlier discoveries of ways to induce genetic mutations in plants. These methods led to modern plant breeding, with momentous results that included the tailoring of crop varieties for regions of climatic extremes. At a research station at Campo Atizapan he developed strains of grain that dramatically increased crop yields. Borlaug ultimately developed short-stemmed
(“dwarf”) wheat, a key element in the Green Revolution in developing countries.

The Green Revolution resulted in increased production of food grains (especially wheat and rice) and was due in large part from the introduction into developing countries of new, high-yielding varieties, beginning in the mid-20th century with Borlaug's work. Its early dramatic successes were in Mexico and the Indian subcontinent. Wheat production in Mexico multiplied threefold in the time that Borlaug worked with the Mexican government. In addition, “dwarf” wheat imported in the mid-1960s was responsible for a 60 percent increase in harvests in Pakistan and India.

Borlaug also created a wheat–rye hybrid known as triticale. The increased yields resulting from Borlaug's new
strains enabled many developing countries to become agriculturally self-sufficient. However, since their introduction, these new varieties have been discovered to require large amounts of chemical fertilizers and pesticides to produce their high yields, raising concerns about cost and potentially harmful environmental effects. As a result, newer varieties of food grains, which are high-yielding and resistant to local pests and diseases, have been developed.

Borlaug served as director of the Inter-American Food Crop Program (1960–63) and as director of the International Maize and Wheat Improvement Center, Mexico City, from 1964 to 1979. In 1986 Borlaug created the World Food Prize as a way to honour individuals who have contributed to improving the availability and quality of food worldwide. In constant demand as a consultant, Borlaug has served on numerous committees and advisory panels on agriculture, population control, and renewable resources.

(b. Oct. 28, 1914, New York, N.Y., U.S.—d. June 23, 1995, La Jolla, Calif.)

A
merican physician and medical researcher Jonas Edward Salk developed the first safe and effective vaccine for polio. Salk received his M.D. in 1939 from New York University College of Medicine, where he worked with Thomas Francis, Jr., who was conducting killed-virus immunology studies. Salk joined Francis in 1942 at the University of Michigan School of Public Health and became part of a group that was working to develop an immunization against influenza.

In 1947 Salk became associate professor of bacteriology and head of the Virus Research Laboratory at the University of Pittsburgh School of Medicine. At Pittsburgh, he began research on polio, an acute viral infectious disease of the
nervous system that usually begins with general symptoms such as fever and headache and is sometimes followed by a more serious and permanent paralysis of muscles in one or more limbs, the throat, or the chest. In the mid-20th century hundreds of thousands of children were struck by the disease every year. Working with scientists from other universities in a program to classify the various strains of poliovirus, Salk corroborated other studies in identifying three separate strains. He then demonstrated that killed virus of each of the three, although incapable of producing the disease, could induce antibody formation in monkeys. In 1952 he conducted field tests of his killed-virus vaccine, first on children who had recovered from polio and then on subjects who had not had the disease; both tests were successful in that the children's antibody levels rose significantly and no subjects contracted polio from the vaccine. His findings were published the following year.

In 1954 Francis conducted a mass field trial, and the vaccine, injected by needle, was found to safely reduce the incidence of polio. On April 12, 1955, the vaccine was released for use in the United States. In the following years, the incidence of polio in the United States fell from 18 cases per 100,000 people to fewer than 2 per 100,000. In the 1960s a second type of polio vaccine, known as oral poliovirus vaccine (OPV) or Sabin vaccine, named for its inventor American physician and microbiologist Albert Sabin, was developed. OPV contains live attenuated (weakened) virus and is given orally.

Salk served successively as professor of bacteriology, preventive medicine, and experimental medicine at Pittsburgh, and in 1963 he became fellow and director of the Institute for Biological Studies in San Diego, California, later called the Salk Institute. Among his many honours was the Presidential Medal of Freedom, awarded in 1977.

(b. June 24, 1915, Bingley, Yorkshire [now West Yorkshire], Eng.—d. Aug. 20, 2001, Bournemouth, Dorset)

B
ritish mathematician and astronomer Sir Fred Hoyle was best known as the foremost proponent and defender of the steady-state theory of the universe. This theory holds both that the universe is expanding and that matter is being continuously created to keep the mean density of matter in space constant.

Hoyle was educated at Emmanuel College and St. John's College, Cambridge, and spent six years during World War II with the British Admiralty, working on radar development. In 1945 he returned to Cambridge as a lecturer in mathematics. Three years later, in collaboration with the astronomer Thomas Gold and the mathematician Hermann Bondi, he announced the steady-state theory. Within the framework of Albert Einstein's theory of relativity, Hoyle formulated a mathematical basis for the steady-state theory, making the expansion of the universe and the creation of matter interdependent. Einstein assumed that the universe as a whole is static—i.e., its large-scale properties do not vary with time. This assumption, made before American astronomer Edward Hubble's observational discovery of the expansion of the universe, was also natural; it was the simplest approach, as Aristotle had discovered, if one wishes to avoid a discussion of a creation event. The notion that the universe on average is not only homogeneous and isotropic in space but also constant in time was philosophically attractive. Hoyle, Bondi, and Gold called it the perfect cosmological principle.

In the late 1950s and early '60s, controversy about the steady-state theory grew. New observations of distant galaxies and other phenomena, supporting the big-bang theory (a phrase that Hoyle had coined in derision in the 1940s),
weakened the steady-state theory, and it has since fallen out of favour with most cosmologists. Although Hoyle was forced to alter some of his conclusions, he tenaciously tried to make his theory consistent with new evidence.

Hoyle was elected to the Royal Society in 1957, a year after joining the staff of the Hale Observatories (now the Mount Wilson and Palomar observatories). In collaboration with William Fowler and others in the United States, he formulated theories about the origins of stars as well as about the origins of elements within stars. Hoyle was director of the Institute of Theoretical Astronomy at Cambridge (1967–73), an institution he was instrumental in founding. He received a knighthood in 1972.

Hoyle is known for his popular science works, including
The Nature of the Universe
(1951),
Astronomy and Cosmology
(1975), and
The Origin of the Universe and the Origin of Religion
(1993). He also wrote novels, plays, short stories, and an autobiography,
The Small World of Fred Hoyle
(1986).

(b. June 8, 1916, Northampton, Northamptonshire, Eng.—d. July 28, 2004, San Diego, Calif., U.S.)

B
ritish biophysicist Francis Crick received the 1962 Nobel Prize for Physiology or Medicine, along with James Watson and Maurice Wilkins, for determining the molecular structure of deoxyribonucleic acid (DNA), the chemical substance ultimately responsible for hereditary control of life functions. This accomplishment became a cornerstone of genetics and was widely regarded as one of the most important discoveries of 20th-century biology.

During World War II, Crick interrupted his education to work as a physicist in the development of magnetic mines for use in naval warfare, but afterward he turned to biology at the Strangeways Research Laboratory, University
of Cambridge (1947). Interested in pioneering efforts to determine the three-dimensional structures of large molecules found in living organisms, he transferred to the university's Medical Research Council Unit at the Cavendish Laboratories in 1949.

In 1951, when the American biologist James Watson arrived at the laboratory, it was known that the mysterious nucleic acids, especially DNA, played a central role in the hereditary determination of the structure and function of each cell. Watson convinced Crick that knowledge of DNA's three-dimensional structure would make its hereditary role apparent. Using the X-ray diffraction studies of DNA done by Wilkins and X-ray diffraction pictures produced by Rosalind Franklin, Watson and Crick were able to construct a molecular model consistent with the known physical and chemical properties of DNA. The model consisted of two intertwined helical (spiral) strands of sugar-phosphate, bridged horizontally by flat organic bases. Watson and Crick theorized that if the strands were separated, each would serve as a template (pattern) for the formation, from small molecules in the cell, of a new sister strand identical to its former partner. This copying process explained replication of the gene and, eventually, the chromosome, known to occur in dividing cells. Their model also indicated that the sequence of bases along the DNA molecule spells some kind of code “read” by a cellular mechanism that translates it into the specific proteins responsible for a cell's particular structure and function.

By 1961 Crick had evidence to show that each group of three bases (a codon) on a single DNA strand designates the position of a specific amino acid on the backbone of a protein molecule. He also helped to determine which codons code for each of the 20 amino acids normally found in protein and thus helped clarify the way in which the cell eventually uses the DNA “message” to build proteins.
From 1977 until his death, Crick held the position of distinguished professor at the Salk Institute for Biological Studies in San Diego, California, where he conducted research on the neurological basis of consciousness. His book
Of Molecules and Men
(1966) discusses the implications of the revolution in molecular biology.
What Mad Pursuit: A Personal View of Scientific Discovery
was published in 1988. In 1991 Crick received the Order of Merit.

(b. April 6, 1928, Chicago, Ill., U.S.)

A
merican geneticist and biophysicist James Dewey Watson played a crucial role in the discovery of the molecular structure of deoxyribonucleic acid (DNA), the substance that is the basis of heredity. For this accomplishment he was awarded the 1962 Nobel Prize for Physiology or Medicine with Francis Crick and Maurice Wilkins.

Watson enrolled at the University of Chicago when only 15 and graduated in 1947. From his virus research at Indiana University (Ph.D., 1950), and from the experiments of Canadian-born American bacteriologist Oswald Avery, which proved that DNA affects hereditary traits, Watson became convinced that the gene could be understood only after something was known about nucleic acid molecules. He learned that scientists working in the Cavendish Laboratories at the University of Cambridge were using photographic patterns made by X rays that had been shot through protein crystals to study the structure of protein molecules.