Africa and Australia are stable continental masses, they have changed little over the ages, while North and South America have experienced episodes of mountain building in what were ancient sea beds and have been joined and separated a number of times as the land bridge through Central America and chains of volcanic islands either moved or were immersed. An understanding of Zamia and its roots in the Americas has long been in a state of confusion. Is the current domain of Zamia a fading relic of a global range, or was Zamia always a local and specialized American phenomenon? Did pre- Columbian Indians confuse the issue even more by establishing populations on remote islands to serve as a food source?

The Yucatan impact. Douglas Henderson

The origins of Microcycas are equally shrouded in mystery. This monotypic genus possesses many ancient traits linking it to Ceratozamia and Zamia, but is not present in the fossil record. Was it's ancestral homeland always restricted to Cuba? That seems unlikely. The Cretaceous asteroid impact in the Yucatan threw a vast fan of deep ocean sediments and fiery debris over western Cuba at the close of the Cretaceous. Deep sea cores in the Atlantic and Caribbean reveal sorted materials, layers of mud, then sand, gravel, and finally huge fragments of stone carried by great waves that were more mud and gravel than water. All life on Cuba, Hispaniola, the perhaps the Antilles must have been scoured away in this calamitous event. It's hard to conceive of even seeds or uprooted trunks surviving a catastrophe of such a scale. 

The devastation in Central America might have been minimized if the impactor had descended at a low angle so that much of the ejecta was directed toward the north and east. Perhaps Microcycas is a rare, uniquely specialized survivor of the precursor of Zamia. During the Pleistocene glaciations, when sea levels were much lower and Cuba and Florida and Central America were all part of one land mass, scattered Microcycas populations might have become established all through the area. When sea levels rose, climates changed, and the main land populations died out, Microcycas was restricted as an island relic. The puzzle remains, what might have been fatal to Microcycas in Mexico or Central America, where the climate has always been very similar to Cuba's? A disease that might have wiped out a specific pollinator?