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Did the first coconuts come from the Americas?
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From whence come coconuts?

by Eric Jackson


The Smithsonian Tropical Research Institute (STRI) is best known as one of the world's top biological research centers, not only at the famous Barro Colorado Island but also at marine laboratories at Galeta Island in Colon and in Bocas del Toro, and scientists working on research projects here and there all over Panama and indeed all over the tropical world. But biology isn't the only thing that STRI does, and one proof of that is the institute's archaeology and paleontology center that's located in the old Gorgas Hospital complex, next door to the judicial morgue and kitty-corner from the Supreme Court.


The boundaries among archaeology (the study of the human past mainly through structures and artifacts left behind), paleontology (the study of fossils) and biology (the study of living things) are regularly blurred at the Smithsonian. Some of STRI's most famous work is by Dr. Dolores Piperno, who by studying the microscopic fossilized starch grains on grinding stones found by archaeologists has been able to discover many new leads to the story of the domestication of corn, pushing the date of that innovation back in time and north in place from the Andes to Meso-America. Biologists studying the nature of evolution frequently get into both the biochemistry of DNA and the fossil records uncovered by paleontologists. By and large STRI scientists are advanced beyond the condition described by Ambrose Bierce as the "specialist who knows everything about something and nothing about anything else" because they tend to be pushing the edges of their specialties beyond previous limits.


And so it is that the occasional Paleo-Talks held at the Gorgas Complex don't just attract paleontologists and the occasional journalist with strange interests. Biologists were also on hand on August 16 to hear Carolina Gómez N. speak about the work that she and STRI staff scientist Carlos Jaramillo have been doing at the Cerrejon open-pit coal mine in Colombia, where layer upon layer of the records of geological time have been laid bare by the earth moving machines.


Gómez has been studying the fossils of palms, plants that have been around a long time but whose scientific family name has relatively recently changed from the old Palmae to Arecaceae in the more modern taxonomy. These are, of course, a family of monocot trees and shrubs with unbranched stems and palmate or pinnate leaves, found mainly in the tropics.


Colombia has the world's richest collection of palms, some 44 genera with 227 species that have been identified and probably some undescribed others lurking out there in the country's jungles and mountains. Likewise, Gómez describes the fossil record of the site she and Jaramillo have been working as "very rich" --- they find the pollen, leaves, fruit and trunks of ancient palms in abundance there.


Fossilized palm species, it seems, are hard to differentiate at a glance. Even under a microscope, Gómez noted, the fossil pollens that are found in the rocks and coal seams are so similar as to be fairly impossible to assign to one species or another. Certain things, however, can be learned from morphologies. The large leaf sizes and drip tips found on the palm fossils at Cerrejon, for example, are dead giveaways that in their lifetimes they existed in a tropical rainforest. Extrinsic geological evidence also reveals that over time and varying by location the primordial palms of Cerrejon sometimes existed next to fresh water, and sometimes next to brackish water.


It is possible, however, when one gets a really well preserved sample of a palm leaf to study the waxy cuticle layer that protected the epidermis. Studied under a microscope using ultraviolet light, distinctive patterns come out in the cuticles, by which different species can be distinguished from one another and fossils can be compared to modern plants.


Palms are thought to have emerged in the Cretaceous period of the Mesozoic era, when dinosaurs walked the earth. The oldest palm fossil yet found was unearthed in South Carolina and dates back some 85 million years, but palms are thought to have originated in Australia. (Bear in mind, however, that continents have drifted around over geologic time, merging and splitting, so that if you think of these plants as having appeared in the modern positions of these places you will have created an inaccurate perception in you mind.) The Mesozoic era and its Cretaceous period ended, most scientists now believe, about 65 million years ago with a mass extinction caused by an object from outer space smashing into our planet near the modern Yucatan Peninsula. Most living things didn't survive, but after awhile the few things that did splintered into myriad species that took over all the various ecological niches that had been filled by other plants and animals in earlier times. Not only mammals proliferated in the Paleoncene epoch that followed the dinosaur extinction, Gómez said. The fossil record indicates a great breakout in palm diversity in that time as well.


Her work is helping to flesh out details of this natural history, and revising earlier estimates of when and how things happened. For example, it has been commonly believed that the spiny and non-spiny clades of palm species split off some 50 to 60 million years ago. But fossils found at Cerrejon indicate that this divergence is older than that, according to Gómez.


This finding also provides the first tantalizing bits of evidence that coconuts originated in South America more than 60 million years ago, rather than at a later date in India as the conventional wisdom would have it.


Coconuts, it seems, are related to nipa fruit, a palm modernly native only to the South Pacific. The Paleocene fossil record shows that there used to be a much wider distribution, with finds in Asia, Africa, Europe, North and South America. The oldest fossil nipa fruit yet found now belongs to a layer of the Cerrejon site that's 60 million years old and it suggests that the ancestors of these palms and and those of the coconuts diverged before that time.


The discoveries will surely be scrutinized and the inferences which Gómez draws from them will surely be contested, as she admits that the oldest fossils of modern coconut fruit go back to the Eocene epoch, which extends from a bit more than 37 million years ago back to about 55 million years ago, and hail from Australia and India. But her studies of fossilized palm frond cuticles through a microscope and under UV light suggest to her that those were just youngsters.  


Also in this section:
Did the first coconuts come from the Americas?
Young people and HIV

Male circumcision and HIV

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