Darwin's Dreampond: Drama in Lake Victoria
Tijs Goldschmidt, translated by Sherry Marx-MacDonald (MIT Press)
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No Mercy: A Journey to the Heart of the Congo
Redmond O'Hanlon (Knopf, Vintage)
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Camping with the Prince and Other Tales of Science in Africa
Thomas A. Bass (Moyer Bell)
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Natural history is the focus of two recent books about Africa, one by a Dutch fish ecologist, the other by a British travel writer. The authors approach Africa with different temperaments, and motives, yet both lead us to lakes where the mysteries of evolution confront the curiosity of the rational Western mind. It is a gift of these books that they do not entirely replace mystery with explanation. A third book, by an American journalist, shows a more practical side of African science, focusing on the search for answers to the continent's problems, from famines and loss of wildlife to new virus outbreaks.
In Darwin's Dreampond, Tijs Goldschmidt offers a fresh, almost breezy account of a young scientist's fieldwork and thoughts, as he tries to bring order to the explosive taxonomy of fish in Lake Victoria and to make sense of the order he discerns. Goldschmidt studied cichlids, locally called furu, a group of small perchlike fish, whose radiation into countless species in Lake Victoria is an ecologist's dream come true.
Lake Victoria's cichlids are akin to Darwin's finches in the Galápagos Islands: in both cases, the variations provided an isolated picture of how adaptation to different niches could lead to the rapid evolution of new species from a common ancestor. But as an endless number of different forms were pulled from the lake in Goldschmidt's nets, the ecologist's dream became a taxonomist's nightmare. "How could I ever learn to distinguish these different fish from each other?" he writes. "Were they in fact biological species? . . . I became increasingly uncertain about what a species was. The longer I reflected on the concept, the vaguer it became." In clear and candid prose, Goldschmidt reviews various theories of how species evolve, and shares his meditations on their shortcomings as well as their explanatory successes. Goldschmidt's accounts of the fish are full of fascinating detail as he introduces us to the fanning out of furu forms: algae scrapers, with file-like jaws to scrape algae from rocks; snail crushers, with an extra set of jaws in their throats powered by strong muscles; scale scrapers, with a long rasp made of 11 rows of teeth that can scrape the protein-rich scales off other fish; two kinds of fish eaters, those that play dead, lying in ambush to attack their approaching prey, and those streamlined for fast attack.
Since furu are "mouth breeders," the females swimming around with their eggs and newly hatched fry in their mouths, some species feed by ramming the mouths of these females and eating the dislodged offspring. And each predator species has developed its own specific way of ramming, hitting the throat or mouth from below, or crashing down on the snout from above.
But Goldschmidt's mind can be as interesting as what it is studying, and it is refreshing that he doesn't hide this from us. "Anyone who works with fish more intensively than with people over a period of years," he confesses, "starts to see different personalities in the various species. The algae-eating philosopher, the snail-swallowing pimp, the larvae-sifting housewife. . . . I projected human qualities onto the fish--an activity considered anathema by every right-minded scientist--and, in turn saw fish in humans. . . ." While shopping at the open market in nearby Mwanza, Goldschmidt reports wryly, "I continually spotted traces of fish personalities in the faces of Africans, Indians, and Europeans. In passing, I whispered their Latin names under my breath."
It is ironic that a book that illuminates the evolution of species in so many ways ends up describing a mass extinction of species. While Goldschmidt collected cichlids to understand their evolution, he found that he had become a witness to an ecological disaster. The Nile perch, a large fish introduced into Lake Victoria in order to improve commercial fishing, almost wiped out the cichlids (Smithsonian, December 1988). "Within a single decade," he writes, "the differentiated biotic community that had coevolved over a period of at least fourteen thousand years, and perhaps even hundreds of thousands of years, had changed into an impoverished mess."
Yet there is a further irony at the book's end. Ecologists assumed that once the Nile perch devoured the cichlids, their numbers would also crash from lack of a food supply. But it didn't happen, because a population of prawns, once dined on by cichlids, exploded and fed the Nile perch. And a new cichlid species began to appear, a kind of hybrid that seems to demonstrate a degree of resistance to the perch. Here again, Goldschmidt reminds us of the errant facts of life, concluding, "Every time we predicted something, the ecosystem surprised us by taking an unexpected turn."