An international team of researchers advancing a new theory about the primordial soup that gave rise to life has paid homage to the "brilliance" of a long-dead Canadian scientist whose insights in the 1920s presciently framed this century's search for the ultimate origin of species.
German biochemist Armen Mulkidjanian led a group of Russian and American researchers that presents evidence in the latest issue of the journal Proceedings of the National Academy of Sciences that life began in shallow pools of condensed vapour near active volcanoes — an idea that runs counter to the prevailing view of an oceanic origin for organic matter, but echoes 19th-century scientist Charles Darwin's famous notion that "some warm little pond" was probably the wellspring of all living things.
However, the new study specifically credits another scientific legend — Ontario-born biochemist Archibald Macallum, founding chairman of the National Research Council of Canada — for a landmark 1926 paper in which he argued that a potassium-rich pool of water would have been crucial in generating those first stirrings of life.
Researchers know that somehow, about 3.7 billion years ago, lifeless minerals became fortuitously mixed in a fluid environment just as some unidentified but necessary energy source — perhaps lightning or the sun, perhaps hydrothermal vents in the sea or volcanic heat on the land — triggered chemical reactions that led to the formation of elemental fatty acids and then to the primitive, unicellular organisms from which all plants and animals eventually evolved.
Mulkidjanian and his team built their research on the premise that the cells of all living things today — by virtue of what they call the "chemistry conservation principle" — preserve vital information about the geological conditions in which life began near the dawn of Earth's history.
As it happens, the same concept was articulated eloquently by Macallum more than 85 years ago, in an article he published in the April 1926 edition of the journal Physiological Reviews.
"The cell," Macallum wrote at the time, "has endowments transmitted from a past almost as remote as the origin of life on earth." The existence of such "paleochemical" traces within living cells, he added, could give biologists — like their colleagues in the field of geology — a window into the primeval conditions on the planet, and foster a new understanding that the "serried ages of the earth's history do not sleep in stone alone."
The paper on cell origins was just one of many highlights in Macallum's stellar scientific career. Born near London, Ont., in 1858, he was not only the founding chair of the NRC — the Canadian government's main science agency — he also served as the inaugural chair in biochemistry for both the University of Toronto and McGill University before his death in 1934.
Mulkidjanian told Postmedia News that he stumbled onto Macallum's 1926 paper late in the preparation of his team's PNAS study, but quickly realized that the Canadian scientist had anticipated several of the key issues still facing 21st-century scientists engaged in origins-of-life research.
"Because of Macallum's brilliance, we have decided to give all the credits to this great scientist, although we had learned about his work in the very last moment," said Mulkidjanian.
Among the central puzzles to be solved is why — if organisms today mimic the chemical conditions of life's beginnings — there's more potassium than sodium in living cells, yet more sodium than potassium in sea water, traditionally seen as the likeliest incubator of life.
Macallum "was the first researcher to frame this question," said Mulkidjanian, adding that in order to "explain the prevalence of potassium over sodium within cells," the Canadian theorized "that the primordial ocean contained much more dissolved potassium than sodium."
Modern science, however, has discounted that possibility, creating a serious knowledge gap for those who cling to the idea that life began in the ocean.
But in their paper, Mulkidjanian and his team propose that "geothermal ponds" in which key mineral ingredients are concentrated and animated by volcanic activity would have served as ideal "hatcheries" for life — and with the required chemical predominance of potassium over sodium.
"In sum, we have addressed the same problem which Macallum had addressed first," said Mulkidjanian. "We, however, suggest a quite different solution."
The team's research is generating debate already in the scientific community, with at least one leading researcher questioning the validity of the "chemistry conservation principle" but another — Harvard Medical School professor Jack Szostak, the McGill-educated winner of the 2009 Nobel Prize for physiology — offering qualified support.
"If there is a reason that a high potassium/sodium ratio is biochemically a good thing, then a pre-biotic scenario that provided such a ratio might have been more favourable for the origin or early evolution of life," Szostak told Scientific American this week in commenting on the Mulkidjanian-led study. "But we can't rule out an origin in a low potassium environment followed by (evolutionary) selection for high internal potassium."
However, Szostak added: "I do not think the oceans were a favourable environment for the origin of life," pointing to how the lower salt content of freshwater would have been more conducive to creating the fatty-acid precursors of living cells.
"The accumulation of organic compounds in ponds is also easier to imagine than in the ocean," Szostak stated, "and geothermally active areas provide numerous advantages, as expressed by the authors."
rboswell@postmedia.com
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New research on origins of life credits long-dead Canadian
