# Method in Action: Wegener and Continental Drift (1912)

> *This example is part of the [occams-razor](../SKILL.md) skill.*

A worked example of the razor — and an honest demonstration of its limits. Not a victory parade.

By the early 1900s, paleontologists had a stubborn pattern of evidence: identical fossil species (*Mesosaurus*, *Glossopteris*) appeared on continents now separated by oceans. The conventional account multiplied entities: vanished "land bridges" between continents, sunken "lost continents," parallel evolution on identical isolated environments, sweepstakes dispersal across thousands of miles. Each new fossil required a new bridge or a new coincidence.

In 1912, the German meteorologist **Alfred Wegener** proposed a simpler account: the continents themselves had moved, and these now-separated regions had once been joined (he called the supercontinent *Pangaea*). One claim explained the fossil pattern, the matching coastlines of South America and Africa, the distribution of certain rock formations, and the matching mountain belts — all at once.

By the razor, Wegener's account is the preferred hypothesis: it fit the evidence with **one** posited mechanism instead of many ad hoc bridges, sinkings, and coincidences. **But the razor does not prove him right.** Wegener could not name a plausible *mechanism* by which continents could drift through ocean basins, and the geological establishment rejected the theory for decades. Both sides were partly correct: the razor preferred Wegener (parsimony), but the **over-shave check was unresolved** (a missing entity — the mechanism — that the evidence ultimately required).

The mechanism was found in the 1960s: **seafloor spreading** at mid-ocean ridges (Harry Hess) and the magnetic stripe pattern across the ocean floor (Vine–Matthews–Morley). Plate tectonics absorbed Wegener's drift, with the mechanism filled in. The razor's bet — held as a prior, pending distinguishing evidence — paid off, 50 years later.

Two lessons for the audit: (1) **the razor gives you what to bet on, not what is true**; (2) **the over-shave check is what tells you the bet is incomplete** — Wegener's missing-mechanism gap was the thing he could not have explained away by appealing to parsimony.

**Sources:** Wegener, A. *Die Entstehung der Kontinente und Ozeane* (1915; English tr. *The Origin of Continents and Oceans*, Methuen, 1924); Hess, H. H., "History of Ocean Basins," in *Petrologic Studies: A Volume in Honor of A. F. Buddington*, Geological Society of America (1962); USGS overview: https://www.usgs.gov/programs/earthquake-hazards/plate-tectonics