Black and white: the bias that shaped plate tectonics and the ongoing > 100 years old divide of the geoscience community

Dichotomous thinking also known as “black-and-white” and “all-or-nothing” thinking is a common cognitive distortion in which one sees things in absolute extremes without any middle ground. Not only does this bias distort reality and lead to interpersonal conflicts, but it also hinders problem solving. In the Geosciences, this bias is the source of a > 100 years old divide between tectonicists, i.e., early supporters of Continental Drift Theory (e.g., Alfred Wegener, Alexander du Toit), and paleontologists, who argued for (now sunken) land bridges between the continents based on similar fossil records (e.g., Charles Schuchert, John Gregory, Hermann von Ihering, Bailey Willis). Despite explaining the similar fossil record on continents now separated by oceans, Land Bridge Theory implied continental fixity. It was therefore completely abandoned in the 60–70s with the growing body of evidence supporting continent motion. Continental Drift Theory was then fully accepted without any middle ground despite the fossil record suggesting prolonged connection between the continents at specific localities. Possible causes for the black-or-white approach of the Geoscience community include (1) simplicity: easier to envision one hypothesis being right rather than a compromise of both, (2) guilt: Alfred Wegener had died in Greenland in 1931 only to be proven right 30 years later upon acceptance of continent motion, and (3) a feeling of inferiority amongst paleontologists and feeling of superiority (i.e., feeling of inferiority in disguise) amongst tectonicists upon demonstrating continental motion.

Since then, paleontologists have explored new hypotheses to explain the migration of species at times when oceans are believed to have fully separated the continents, e.g., migration of primates from western Africa to South America and of lizards the other way around in the Oligocene. A hypothesis under testing involves floating vegetation islands rafting the species as small groups of individuals across the ocean. This hypothesis implies that enough individuals survived the crossing, i.e., enough food and/or quick journey, and found one another upon landing.

Neither the new hypotheses nor the old ones take into account all the evidence, e.g., microcontinents along major transform faults (e.g., Romanche and St Paul fault zones) and correlation of all former land bridges with major transform faults and rift-oblique orogens on the adjacent margins (e.g., Central African Orogen in western Africa and Sergipano Belt in northeastern Brazil). Orogenic Bridge Theory reconciles these with both continent motion and the fossil record. Orogenic bridges are ribbons of continental crust transected by orogenic structures highly oblique to the active rift. These structures are unsuitably oriented to thin the crust and thus hinder rifting, delay breakup, and control the formation of major transform faults and elongated microcontinents. Orogenic bridges have the potential to form prolonged land connections between the continents while oceanic crustal domains form on either side, thus further allowing the spreading of terrestrial species while hindering that of marine species. This illustrates the need for more multidisciplinary collaboration across the geosciences. Creating a more flexible community that is both inclusive and mindful of diversity is key to enhance collaboration.