The Earth’s landmasses and their respective biotas had always been in the current configuration. It seemed inconceivable to most scientists that cartographic features of the planet had changed much across evolutionary time.
biotas; continental drift
The Earth’s landmasses and their respective biotas had always been in the current configuration. It seemed inconceivable to most scientists that cartographic features of the planet had changed much across evolutionary time.
In 1912, the German geophysicist/meteorologist Alfred Wegener published a provocative article speculating that the planet’s continents had formerly been united (into a supercontinent Pangea) before they splintered and slowly plowed across the Earth’s surface to their present-day positions. This hypothesis became known as Wegener’s theory of continental drift. Wegener backed his idea – which got a hostile reception at the time – by several lines of empirical evidence: continental shapes that fit together like pieces of a jigsaw puzzle; particular resemblances between the biotas on apposite landmasses, such as those on alternate sides of the Atlantic Ocean (some of these similarities previously had been attributed to hypothetical land bridges); and a matching alignment of geological formations on the respective landmasses, such as similar rock strata in the Appalachian Mountains of North America and the Scottish Highlands. Wegener’s theory languished for several decades until – in the 1950s and 1960s – it received compelling support from detailed geophysical explorations of the Earth’s crustal movements (plate tectonics). Today, continental drift is widely accepted as a geological fact beyond dispute, and the precise rate of modern crustal movements (typically several centimeters per year) can even be monitored directly using satellite and other global-positioning technologies.
Wegener’s ideas eventually were to revolutionize thought in geology and paleontology. They also dovetailed nicely with some of the biological concepts that had been implicit in various of Wallace’s biogeographic principles (see Chapter 6). In evolutionary genetics, Wegener’s insights understandably had a lesser impact, except insofar as they helped to promote the broader realization that biogeographic patterns and processes (see Chapter 51) must take into account the surprisingly dynamical nature of the Earth’s historical geology and physiography.
1. Wegener AL. Die entstehung der kontinente [The formation of the continents]. Geologische Rundschau. 1912;3:276–292.
2. Wegener AL. 1968. The Origin of Continents and Oceans [translated from a later edition of a book originally published in German in 1915]. Mathuen, London, UK.