Reef Madness: Charles Darwin, Alexander Agassiz, and the Meaning of Coral
- David Dobbs
Reefs have long fascinated natural historians and geologists for their unearthly beauty, as well as their ability to produce prodigious amounts of carbonate sediment. Yet reefs offer more than their share of paradoxes. How do coral-reef islands seemingly grow from great depths in the middle of the oceans? What controls the production of all this limestone? And why do so many reefs form necklaces strung across the Pacific? These questions troubled the minds of nineteenth-century scientists and philosophers. The long, tortured and often sad history of how the ‘coral reef problem’ was finally solved is laid bare in this eloquent and thoughtful book.
We are first introduced to the key figures: Louis Agassiz, his son Alexander and Charles Darwin. The book explores in detail the meteoric rise and fall of the arrogant, narcissistic and charismatic Louis, and his relationship with his shy and diligent son. Louis, a palaeontologist, was the first to propose that an ice age could explain many features of the Earth's surface. In the mid-nineteenth-century United States, which was hungry for pioneering personalities that embodied the spirit of a young nation, Louis' enormous energy and persuasive vision enabled him to found many scientific institutions that still thrive today. Darwin, by contrast, is presented as a distant figure, more a man with a following than a personality.
It was Louis' failure to embrace the implications of Darwin's Origin of the Species, instead tenaciously holding on to his idealistic logic that God had created all species whole and immutable, that toppled him from his pedestal in American scientific and Boston blue-blood society. In just five years Louis was transformed from being seen as the prince of US science to an archaic reactionary.
As a young man, Alexander was caught between paternal loyalty and a great personal need for objective and careful analysis. He rejected his father's florid unscientific style but was equally unhappy with Darwin's theorizing, which was based, as Alexander saw it, on equally unacceptable flights of imagination, rather than on the tireless compilation of meticulously observed facts.
Darwin had been greatly influenced by the geologist Charles Lyell, whose major tenet was that geological structures, rather than being the result of past catastrophes, were instead formed by the constant action of slow and gradual processes observable today. It is easy to see how such thinking led to Darwin's formulation of another time-based phenomenon: the origin of multiple species through common descent by means of natural selection. Darwin's observation of Pacific reefs, together with his harrowing experiences of the Earth-moving forces of earthquakes during the voyage of the Beagle, led him to propose that oceanic reefs and atolls were formed on subsiding foundations, such as volcanoes. His imaginative intellect saw here another result of small changes that could account for otherwise complex patterns: that there was a dynamic relationship between the reefs and their foundations that seemed to shape them. But proof for this theory was there none.
So the stage was set for a century-long battle for the roles of empiricism, theorizing and imagination in scientific endeavour. In 1876, the Scottish oceanographer John Murray had put forward an alterative coral-reef hypothesis. He proposed that reefs grew not on their own debris, but on the accumulation of sediment derived from plankton and other non-coral skeletons. Alexander Agassiz was immediately drawn to this idea: it was born of neither his father's idealism nor Darwin's over-simple theorizing, but seemed instead to be based firmly on observable fact. Alexander, grief-stricken by the early loss of his wife and other relatives, had finally found his raison d'être: to disprove Darwin's theory.
Made hugely wealthy from the ownership of copper mines, Alexander was able to embark on a massive programme of travel. For decades he made detailed observations of all the known coral reefs. He was convinced that each reef was a unique outcome of forces that combined in different ways: no single grand theory was required. By 1902, he believed he had proved Murray's theory. Yet astonishingly, after his death in 1910, no manuscript that summarized his massive accumulation of observations was ever found. It seems that for Alexander, the chase was everything.
The truth is that there were never enough facts to go on. All the protagonists had died long before the origin of reefs was resolved by deep drilling in the 1950s. The penetration of Eniwetok atoll down to its volcanic foundations revealed some 1,500 metres of coral reef limestone, proving Darwin right.
Reef Madness is more than a narrative about the victory of empiricism, the power of observation as the evidence of truth, over the philosophy of belief. It is also a beautiful illustration of how theories can, or must, be built slowly and painfully, brick by brick, by a dynamic combination of both imaginative leaps and factual observation. It would be foolish to think that this debate has ended: as the author points out, 150 years later, over half of Americans continue to believe that God has either created species or directs evolution in some way. It seems that science and the human condition will always need a beautiful idea.
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Wood, R. The evolution of scientific thinking. Nature 435, 25–27 (2005). https://doi.org/10.1038/435025a
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