Daily Archives: 1 November 2014

November 1, 1977 (a Tuesday)

Carl Woese

On this date, the American microbiologist and physicist Carl Woese published a report in the Proceedings of the National Academy of Sciences (PNAS) in which he defined the Archaeabacteria (a new super-kingdom of life) by phylogenetic analysis of 16S ribosomal RNA.  This technique was pioneered by Woese and is now standard practice. By 1990 Woese shortened the name Archaebacteria to Archaea and adopted the term “domains” for the three new branches of life: Bacteria, Archaea, and Eukarya. Archaea are neither Bacteria nor Eukaryotes. In other words, they are Prokaryotes that are not Bacteria. More than twenty kingdoms exist under the domains in the tree of life, far more than the five original kingdoms suggested by R.H. Whittaker in 1969. In fact, Woese found that Archaea are more closely related to Eukarya (plants, animals, fungi, etc.) than to Bacteria. This accounted for the renaming of Archaebacteria, the original name given by Woese, to Archaea.

According to Woese:

The archaea are unique organisms. While prokaryotes in the cytological sense, they are actually more closely related to eukaryotes than to the bacteria. They are of particular interest for this reason alone-they are simple organisms whose study should provide insights into the nature and evolution of the eukaryotic cell. Their study is also central to an understanding of the nature of the ancestor common to all life. The archaea are, of course, interesting in their own right. The group contains both the methanogens and numerous organisms that grow at extremely high temperatures (in some cases above 100°C). As such, they provide potential insights into mechanisms of thermophilia and methanogenesis.

by Carl Woese

The acceptance of the validity of Woese’s classification was a slow and painful process. Famous figures, including Salvador Luria and Ernst Mayr, objected to his division of the prokaryotes. Not all criticism of him was restricted to the scientific level. Not without reason has Woese been dubbed “Microbiology’s Scarred Revolutionary” by the journal Science. The growing amount of supporting data led the scientific community in general to accept the Archaea by the mid-1980s. A shrinking minority of scientists still adhere to concepts of evolutionary radiation, but Woese appears to have been vindicated in his convictions.

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November 1, 1880 (a Monday)

Alfred Lothar Wegener

On this date in Berlin was born Alfred Lothar Wegener, a German meteorologist and geophysicist who first gave a well-developed hypothesis of continental drift. In 1912, he presented a paper entitled “Die Herausbildung der Grossformen der Erdrinde (Kontinente und Ozeane) auf geophysikalischer Grundlage” (“The geophysical basis of the evolution of large-scale features of the earth’s crust”) before the Geological Association of Frankfurt am Main. He suggested that all the present-day continents came from a single primitive land mass, the supercontinent Pangaea, which eventually broke up and gradually drifted apart about 250 million years ago. (A similar idea was proposed earlier by F.B. Taylor in 1910.) It was expanded in 1915 into Die Entstehung der Kontinente und Ozeane (The Origin of Continents and Oceans), the first comprehensive account of the theory of continental drift. Others saw the fit of coastlines of South America and Africa, but Wegener added more geologic and paleontological evidence that these two continents were once joined.

Just like the initial reaction in the scientific community to the idea of evolution in the eighteenth century (see Jean-Baptiste Lamarck), reaction to Wegener’s theory was almost uniformly hostile, and often exceptionally harsh and scathing; Dr. Rollin T. Chamberlin of the University of Chicago said, “Wegener’s hypothesis in general is of the footloose type, in that it takes considerable liberty with our globe, and is less bound by restrictions or tied down by awkward, ugly facts than most of its rival theories.” Part of the problem was that Wegener had no convincing mechanism for how the continents might move.

In the fourth edition of his book, The Origins of Continents and Oceans (1929), Wegener wrote:

Scientists still do not appear to understand sufficiently that all earth sciences must contribute evidence toward unveiling the state of our planet in earlier times, and that the truth of the matter can only be reached by combing all this evidence. . . It is only by combing the information furnished by all the earth sciences that we can hope to determine ‘truth’ here, that is to say, to find the picture that sets out all the known facts in the best arrangement and that therefore has the highest degree of probability. Further, we have to be prepared always for the possibility that each new discovery, no matter what science furnishes it, may modify the conclusions we draw.

Beginning in 1906, interested in paleoclimatology, he went on several expeditions to Greenland to study polar air circulation. Wegener made what was to be his last expedition to Greenland in 1930. While returning from a rescue expedition that brought food to a party of his colleagues camped in the middle of the Greenland icecap, he died, a day or two after his fiftieth birthday. Wegener’s theory found more scattered support after his death, but the majority of geologists continued to believe in static continents and land bridges.

Increased exploration of the Earth’s crust, notably the ocean floor, beginning in the 1950s and continuing on to the present day, has provided overwhelming evidence for the mechanism by which the continents move, called plate tectonics. By the late 1960s, plate tectonics, as well as continental drift, was well supported and accepted by almost all geologists.