Elsevier

Endeavour

Volume 30, Issue 4, December 2006, Pages 131-137
Endeavour

Review
Deserts on the sea floor: Edward Forbes and his azoic hypothesis for a lifeless deep ocean

https://doi.org/10.1016/j.endeavour.2006.10.003Get rights and content

While dredging in the Ægean Sea during the mid-19th century, Manxman Edward Forbes noticed that plants and animals became progressively more impoverished the greater the depth they were from the surface of the water. By extrapolation Forbes proposed his now infamous azoic hypothesis, namely that life would be extinguished altogether in the murky depths of the deep ocean. The whole idea seemed so entirely logical given the enormous pressure, cold and eternal darkness of this apparently uninhabitable environment. Yet we now know that the sea floor is teeming with life. Curiously, it took 25 years for the azoic hypothesis to fall from grace. This was despite the presence of ample contrary evidence, including starfishes, worms and other organisms that seemingly originated from the deep seabed. This is a tale of scientists ignoring observations that ran counter to their deep-seated, yet entirely erroneous, beliefs.

Section snippets

The azoic hypothesis

Cruising in the Ægean Sea looking for weird and wonderful life-forms on the seabed, Edward Forbes (Figure 1) had an unparalleled opportunity to pursue his great interest – the distribution of animals and plants in the sea. The year was 1841 and Forbes, a brilliant naturalist who is considered by many to be the founder of British marine biology, had boarded the HMS Beacon under the captaincy of Thomas Graves as part of a surveying mission to the eastern Mediterranean. Dredging in deep water in

Evolution of an idea

Born on 12 February 1815, it was not long before the romantic beauty of his native Isle of Man was to captivate the young Forbes and inspire him as a naturalist. He spent hours arranging, classifying and drawing all manner of objects, including minerals, fossils, shells, dried sea-weeds, hedge-flowers and dead butterflies. Indeed, by the age of 12 he had founded a museum in his own home, and at 16 he left home for London intending to become an artist. The Royal Academy refused to admit him.

Counter evidence

As early as 1818, decades before Forbes’ adventures in the Ægean, evidence that might have discredited the azoic hypothesis began to accumulate. Captain John Ross RN (1777–1856), sailing in the Isabella, made a series of soundings off the northeast coast of Canada in the region of Baffin's Bay when searching for the elusive northwest passage. He calculated depth using a sounding line lowered over the side of the ship on the end of which was attached a snapping device known as a ‘deep-sea clamm’

Believing the impossible

The endurance of the azoic hypothesis in the face of counter evidence is a good example of the so-called ‘theory ladenness of observation’ [23]. Prejudiced by the notion that life would be impossible in the extreme environment of the deep sea, naturalists embraced Forbes’ hypothesis and simply disregarded evidence to the contrary. Matters were not helped by the fact that much of the counter evidence was not collected in purpose-built dredges, with naturalists reluctant to accept evidence that

The benefits of false hypotheses

The controversy surrounding the azoic hypothesis was not so much due to problems with the theory itself, but rather the reluctance of many contemporary scientists to accept contradictory evidence. By proposing it, Forbes paved the way for later discoveries by stimulating the debate among leading naturalists of the day about how the marine environment influences the distributions of the plants and animals that live in it. For theories, including erroneous ones, are absolutely necessary for the

References (26)

  • E. Forbes

    On the light thrown on geology by submarine researches; being the substance of a communication made to the Royal Institution of Great Britain, Friday Evening, the 23d February 1844

    Edinburgh New Philosophical Journal

    (1844)
  • E. Forbes et al.

    The Natural History of the European Seas

    (1859)
  • E. Forbes

    Report on the Mollusca and Radiata of the Aegean Sea, and on their distribution, considered as bearing on geology

    Report of the British Association for the Advancement of Science for 1843

    (1844)
  • Von Humboldt, A. (1850) Views of Nature: Or Contemplations on the Sublime Phenomena of Creation (Otté, E.C. and Bohn,...
  • E. Forbes

    Report on the distribution of Pulmoniferous Mollusca in the British Isles

    Report of the British Association for the Advancement of Science for 1839

    (1840)
  • E. Forbes

    On the associations of Mollusca on the British coasts, considered with reference to Pleistocene geology

  • H.T. De La Beche

    Researches in Theoretical Geology

    (1834)
  • L. Agassiz et al.

    Outlines of Comparative Physiology

    (1851)
  • D. Page

    Advanced Text-book of Geology

    (1856)
  • J.F. Grassle et al.

    Deep-sea species richness – regional and local diversity estimates from quantitative bottom samples

    American Naturalist

    (1992)
    M.V. Angel

    Ocean diversity

  • Peres, J.M. (1982) Major benthic assemblages. In Marine Ecology (Vol. 5, Part 1) (Kinne, O., ed.), pp. 373–522, John...
  • E. Forbes

    On the dredge

    P.F. Rehbock

    The early dredgers: ‘naturalizing’ in British Seas, 1830–1850

    Journal of the History of Biology

    (1979)
  • J. Ross

    A Voyage of Discovery, Made Under the Orders of the Admiralty, in his Majesty's Ships Isabella and Alexander, for the Purpose of Exploring Baffin's Bay, and Inquiring into the Probability of a North-West Passage

    (1819)
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