Not everyone buys the new time frame. Geologist Tony Coates, a former director of scientific research programs at the Smithsonian Institution who fathered the original theory 30 years ago, says Jaramillo's team "has done some beautiful geology," but has ignored earlier lines of evidence, such as the genetics of fossil organisms on either side of the isthmus. Coates is mostly retired, but plans to write a rebuttal. Nevertheless, he says, these new questions are important to answer because the rise of the isthmus was the "last big episode of global change."
The effect of a new land mass on ocean currents is remarkably tricky to understand. Supercomputers in France have been examining how close the continents had to be before currents changed. The preliminary results, analyzed by paleoclimatologist Pierre Sepulchre of the Climate and Environment Laboratory, suggest that with any channel deeper than 200 meters currents behave as though there's an entire ocean there. But at shallower depths currents abruptly hit a wall. The surprise finding: at less than 50 meters currents arise that have never before been simulated.
As for Panama's role as a transcontinental bridge, biologists in Colombia and Sweden have conducted a meta-study examining migration between the Americas. They've found a bump in animal migration three million years ago, but a spike in flora migration 10 million years ago, in support of the revisionist time frame. It is not so unusual for plants to cross where animals dare not tread. The famous 19th-century naturalist Alfred Russel Wallace discovered that animals do not cross the strait separating Bali and Lombok, as if observing an invisible line.
Jaramillo's team aims to gain more insight into these subtleties in the next two years, as Canal Zone excavations continue. But they have a longer lens in mind as well: They have been setting aside hundreds of rock samples in hopes that future scientists can study them with yet-to-be-developed geologic dating methods. After all, it could be decades before geologists have another chance to delve physically into Panama's ancient history, Jaramillo says.
"Most of the rocks we have seen in the past three years have already gone," Jaramillo says. "Some entire mountains that we used to collect from two years ago are now 50 meters below water. So we know we're in a race against time."