Darwin’s theory of evolution is supported and defended throughout Hen’s Teeth and Horse’s Toes. Gould argues the roles that genetics and environment play in the drama of evolution, drawing on the work of William Bateson. Gould addresses debates occurring within evolutionary theory, the political and nonintellectual controversy beginning to stir anew in 1980. Behavior, both inherited and learned, is explored as an adaptation to local environments.
Gould’s first essay, “Big Fish, Little Fish,” introduces the female anglerfish and its dwarf male partner as a delivery system for sperm. A one-and-a-half-inch male anglerfish imbeds itself into a ten-inch female. The two fish become one unit, sharing tissue. The fused male depends on the female for nourishment and provides sperm to ensure a new generation and the continuity of the species. In the second essay, “Sensible Oddities,” Gould writes of the carnivorous nature of parasitic wasps, quoting experts in the field. The female wasp often displays what humans deem cruel and immoral behavior in order to lay its eggs and feed its young.
In the last chapter of this trilogy, “The Guano Ring,” Gould compares the inflexible intelligence of most animals, with decisions made as a result of certain signals, with that of humans, who decide using rational thinking. For example, birds know how to care for only the young that are inside their nests. On the Galápagos Islands, the blue-footed booby nests on a bed of guano (droppings). Squirting guano all around to produce a symmetrical white ring to mark its nest, it lays its eggs. One to three eggs are laid, which...
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