However, there is additional conflicting evidence.
The lead author of the latest research paper is Camilo Montes of the institute with eight other academics.
The time when the isthmus joined North and South America has seemed to be settled science at about 3 million years, and a number of research efforts accept these dates as fact. The Smithsonian said that the joining radically altered the world’s climate and set the scene for a great interchange of plants and animals from north to and from south.
Genetic studies of marine organisms separated by the formation of the Isthmus are all based on research by the Panama Paleontology Project that sets the date for the connection at about 3 million years ago, the institute noted.
The new research is controversial and suggests a much earlier uplift of most of the isthmus. The paper finally has been published online by the Bulletin of the Geological Society of America in its Jan. 13 issue. This is the second paper on the topic, and a third and final effort is due soon. This completes a series of articles that outline a new model for the evolution of Panamá, said the institute.
The new research uses reports from 2,000 fields stations and some 70 analyses, including some for the search for petroleum. “This data set suggests that the isthmus was an uninterrupted chain above sea level from late Eocene until at least late Miocene times,” said an abstract prepared by the Geological Society of America.
On the other hand, another Smithsonian Institute researcher has found a 2.3 meter marlin fossil in the Panamá Caribbean tidal zone. Such fish are typical of the open ocean and the deep seas, the institute said. The researcher, Carlos De Gracia, inadvertently thrust himself into the debate over the uplift of the Isthmus of Panama and suggests that six million years ago, marlin were common in a deep ocean environment at the Caribbean entrance of the current canal, said the institute. The fossil claims a Central American record for the most-complete marine vertebrate fossil yet discovered, said the Smithsonian.
Serious researchers do not doubt that the isthmus was lifted above sea level by tectonic activity, that is the movement of the plates on which the continents ride. The open question now is did the isthmus close 3 million years ago at the start of the current ice age or much earlier.