Giant islands now submerged could explain ancient migration in the Americas
Here’s a mystery: Ancient fossils show animals native to South America in the Antilles Islands off Central America, but how did they cross the sea? The answer is via land masses that have long since disappeared from view under the ocean, according to a new study.
These animals certainly wouldn’t have been able to swim several hundred kilometers of the Caribbean Sea, so they floated above. on hushed vegetation flowing over rivers, where there were once land bridges in place which are now gone.
The new research supports the second hypothesis, suggesting that tectonic plate movements and the spread and shrinkage of glaciers over millions of years may have provided a path for wildlife.
“The Caribbean, including the Greater and Lesser Antilles located at the northeastern end of the Caribbean plate, is considered one of the most important centers of island biodiversity,” the researchers write in their published article.
“Despite decades of study, however, the phylogenetic origins and historical biogeography of this amazing biodiversity remain controversial.”
The team modeled some 40 million years of tectonic plate movement around the junction between the Lesser Antilles, the Greater Antilles, and the Aves ridge submarine mountain, demonstrating how land masses could form and decompose again.
The emergence and disappearance of these archipelagos and “mega-islands” would also have been affected by the rise and fall of sea level, controlled by the melting of glaciers – something else that scientists have modeled over a period of 1.5 million years old.
The researchers took into account seismic data collected in the region over the past 40 years in the calculations, as well as the current geography of the islands. The team was able to work backwards towards the late Eocene period, matching the shores of the islands to the time when they would have emerged from the ocean.
“These periods of emergence may have favored the existence of episodic mega-islands and transitory land links between the Greater Antilles, the Lesser Antilles and the northern part of the Aves ridge (Saba Bank)”, write researchers.
“During the Pleistocene, archipelagos and mega-islands formed repeatedly during maximum glacial episodes.”
These land bridges are more common than you might think, have been around for millions of years and then disappear for millions more. There was once a connection between Russia and Canada, for example, and between the UK and the rest of Europe.
While the idea of land masses in the West Indies region was proposed before, no one has looked at so many details in this particular area. In the future, the researchers want to use the same techniques to extend their models south and cover the entire Caribbean plate.
For now, there is still work to be done around the Lesser Antilles – a more complete terrestrial fossil record and better reconstruction of the ancient geography of the region between Guadeloupe and Venezuela is needed to more precisely trace the paths that once existed.
“The role of the Lesser Antilles in the dispersal of terrestrial fauna over the past 40 million years must therefore be reassessed”, conclude the researchers.
The research was published in Earth-Science Reviews.