“It has never happened” cannot mean “It can never happen”

The expression “It has never happened” cannot mean “It can never happen” rejects the comforting but faulty assumption that an event’s absence from experience makes it impossible. The passage turns that distinction into a warning about biological change: populations can grow, reach a peak, and collapse with a speed and scale that past stability does not rule out.

The Difference Between Precedent and Possibility

The argument begins by insisting that “It has never happened!” cannot be construed to mean, “It can never happen!” Its paired analogies expose the error: never having broken a leg does not make a leg unbreakable, just as never having died does not make a person immortal. In each case, an untested possibility is mistaken for a guarantee. The expression therefore cautions against treating a limited record of experience as proof that a future event cannot occur.

Population Fluctuations

The passage applies the principle to species whose numbers can increase dramatically and then fall just as sharply. It points first to plagues of locusts or Grasshoppers, and then to higher animals: lemming populations follow cycles, while Rabbits can build up over several years until they seem ubiquitous before their numbers suddenly plunge. Some zoologists, the passage adds, have suggested a broader biological law: that the number of individuals in a species is never constant but rises and falls. Under this proposal, the more slowly a species reproduces, the longer its period of fluctuation. The claim is presented as a suggestion, not as an established certainty; its force lies in challenging the assumption that apparent stability will continue indefinitely.

The African Buffalo as an Example

The African buffalo makes the argument historical and specific. During most of the nineteenth century it was common on the veldt, powerful, and subject to few natural enemies. A census taken decade by decade would, the passage says, have shown its numbers steadily increasing. Toward the century’s end, that growth reached a climax; then rinderpest struck, leaving the buffalo almost a curiosity and causing it to disappear from many parts of its range. In the passage’s account, its numbers have slowly built up again over the last fifty years. The sequence—abundance, sudden devastation, and gradual recovery—shows why a species’ previous success cannot be taken as protection against collapse, and why a collapse need not be its final state.