Smithsonian Science » prehistoric

Amazon farmers who vanished centuries ago were remarkably innovative

John Barrat — Mon, 19 Apr 2010 05:28:35 +0000

Little is known about the long-vanished Arauquinoid, an Indian culture that thrived centuries ago in French Guiana, other than they were innovative farmers. The Arauquinoid were gone long before Columbus landed in the new world, yet what archaeologists and other scientists have recently learned about their farming methods comes through the auspices of some unlikely collaborators—ants, termites and earthworms. In addition, what scientists are learning about Arauquinoid farming methods may have important implications for today’s sustainable farms.

Image right: A pre-Columbian raised field in French Guiana filled with small, round mounds for growing crops.

Centuries ago these natives grew maize, manioc and squash upon a matrix of raised beds in flat, regularly flooded coastal marshes. Scooping slices of topsoil from the marsh they flipped them together and upside down, creating mounds which they topped with soil from other areas. Crops were planted, tended and harvested on this matrix of small islands.

Using aerial photographs, researchers have recently located a number of long abandoned “fossil” agricultural fields used by the Arauquinoid in coastal French Guiana. Follow-up examination of the soil and associated fragments from cooking implements, done in part by scientists at the Smithsonian Tropical Research Institute in Panama, have revealed microscopic starch grains from corn and manioc. Squash phytoliths also were recovered from soil analysis.

Image left: The aerial photograph at top shows different types of raised fields in a complex in French Guiana. The bottom image is an interpretation of these earthworks based on stereoscopic ananlysis and field studies.

This new research has revealed that in areas considered unsuitable for farming today, “pre-Columbian farmers constructed thousands of raised fields in the seasonally flooded coastal savannas of the Guianas,” scientists write in a paper published recently in the Proceedings of the National Academy of Sciences. ”They built conspiciuous earthworks, including raised fields, canals and ponds, that enabled them to practice intensive permanent agriculture in this low-lying region with highly seasonal rainfall.” The study combined archeology, archeobotany, paleoecology, soil science, ecology and aerial imagery and was carried out by scientists from a number of organization, including the University of Bayreuth in Germany, the University of Montpellier II and Centre d’Ecologie Fonctionnelle et Evolutive in France, the University of Exeter, and the Smithsonian Tropical Research Institute in Panama.

Image right: A matrix of raised mounds in an abandon field in a part of French Guiana named Savane Grande Macoua. Only the mounds are above water level.

In a region that receives on average four meters of rain each year, scientists were puzzled why the mounds have not eroded into obscurity over the centuries. They discovered that ants and termites, living in the raised mounds since before they were abandoned by the Arauquinoid, have continually rebuilt them with large quantities of new organic matter. Earthworms, attracted to this rich soil, kept the mounds porous, allowing rain to percolate through without washing them away. Grasses and other plants keep the mounds stable. A survey of the ants and termites in these former agricultural swamps, revealed that their nests occur entirely on the mounds, with none in the low, often submerged, areas surround them.

Researchers now speculate that as the fertility of the mounds decreased with continued crop growing, these ancient farmers may have let their mound-matrix fields lay fallow, allowing ants, termites and worms to replenish the soil’s nutrients. This largely forgotten practice of growing crops in marshes and allowing ecological engineers such as ants and termites to replenish nutrients is a technique that may have practical uses in modern sustainable farms, the researchers write.

Prehistoric pollination: Sawfly mouthparts fit tubular channels of gymnosperm cones

John Barrat — Fri, 06 Nov 2009 17:40:15 +0000

Scientific evidence shows that almost all of the earliest angiosperms (flowering plants) were pollinated by insects. Whether such a relationship existed between insects and early gymnosperm species (non-flowering plants with exposed seeds, such as conifers) has been widely disputed. Smithsonian scientists and colleagues, however, have recently found evidence that gymnosperm plants shared an intricate pollination relationship with scorpionfly insects 62 million years before flowering plants appear in fossil records. The team’s findings are published in the scientific journal Science, Friday, Nov. 6.

Illustration: Eurasian mid Mesozoic scorpionflies feeding on gymnosperm ovulate organs, each with tubular access to deeper-seated rewards such as nectar or pollination drops. (Illustration by Mary Parrish)

Conrad Labandeira, paleoentomologist at Smithsonian’s National Museum of Natural History, and team members examined both the specialized features of scorpionfly mouthparts and the unique reproductive features of coexisting gymnosperm plants. The proboscis (elongated tubular mouthparts) of these insects, which was up to 1.3 centimeters long, was either hairy or had ridges, and frequently had pads at the tip to suck up fluids, similar to the structure of modern hoverflies, moths and butterflies. The presumed gymnosperm hosts bore deep funnel-like or tubular channels, also up to 1.3 centimeters long, containing nectar-like pollen drops.

The reproductive anatomy of the plants was typically gymnospermous, but show important modifications for insect attraction, similar to modern flowering plants. However the lineages of these plants and their scorpionfly pollinators became extinct during the mid-Cretaceous period (approximately 105 million years ago) just as flowering plants and their newly evolved pollinators, such as moths and butterflies, came on the scene.

Photos: Lichnomesopsyche gloriae (Mecoptera: Mesopsychidae), from the late Middle Jurassic of northeastern China, showing head and long, hairy proboscis. (Photos by Wenying Wu)

“This exciting discovery now answers the conclusions that paleobotanists were making recently regarding ‘strange’ structures occurring in the ovulate organs of some Mesozoic gymnospermous plants,” said Labandeira. “One such fructification of an extinct Early Cretaceous cheirolepidiaceous conifer family, Alvinia bohemica, is the best example of an anatomically complicated, jerry-rigged device to achieve insect pollination. There were contemporaneous, matching, elongate insect mouthparts, and other evidence, that indicate presence of a gymnosperm-based pollination mode from the deep past.”

The evolution of this type of elongated mouthpart among insects occurred at least five separate times during a 13-million-year span during the Middle Jurassic period. The pollinating relationship between modern pollinators and flowering plants was an independent evolutionary occurrence, separate from the scorpionfly and gymnosperm plants.

Julia Child prepares “Primordial Soup” at the Smithsonian

John Barrat — Thu, 29 Oct 2009 18:56:42 +0000

Fossil teeth of 15-million-year-old browsing horse found in Panama Canal excavations.

John Barrat — Wed, 22 Jul 2009 08:10:19 +0000

The fossil teeth of a 15- to 18-million-year-old three-toed browsing horse, Anchitherium clarencei, were recently discovered by scientists from the Smithsonian Tropical Research Institute and the University of Florida. They found the teeth during excavations of newly exposed rock in the earthworks of the Panama Canal. Bruce MacFadden, curator of vertebrate paleontology at the Florida Museum of Natural History, University of Florida in Gainesville, described the fossil in a recent issue of the Journal of Paleontology.

Photo: This fossil of Anchitherium clarencei, found in the Panama Canal earthworks, is now in the collection of the University of Florida. (Photo courtesy Aldo Rincon)

The discovery significantly extends the southern tip of the known range of this prehistoric animal, and adds to previous fossil evidence discovered in strata from roughly the same period in Florida, Nebraska and South Dakota. It is by far the most complete fossil of a horse collected at the canal site in excavations spanning the last century; characteristics such as the shape of the horse’s teeth indicate it was primarily a forest-dwelling browser. This evidence supports MacFadden’s belief that the habitat of Panama was once a mosaic of relatively dense forest and open woodlands.

The ongoing excavation of the Panama Canal waterway to make the canal wide enough for supersized cargo ships has been a dream come true for Carlos Jaramillo, senior scientist at the Smithsonian Tropical Research Institute in Panama, and his colleagues. Jaramillo, working with the University of Florida and the Panama Canal Authority, organized a team of researchers and students who rush in to map and collect newly exposed fossils in the canal earthworks following large dynamite blasts set off by canal excavators. It was during one of these collecting excursions that Aldo Rincon, a paleontology intern at the Tropical Research Institute, unearthed the fossil teeth of Anchitherium clarencei.

Photo: Following blasting to expand the Panama Canal, geologists and paleontologists organized by the Smithsonian Tropical Research Institute rush in to map, describe and recover any fossils they can find that might reveal more about the prehistoric ecology of Panama.

The Panama Canal excavation site “is one of very few places in the tropics where we have access to fresh outcrops before they are washed away by torrential rains or overgrown by vegetation,” Jaramillo says.

“We expect the fossils that we have been salvaging to resolve some major scientific mysteries, such as: What geological forces combined to create the Panama land bridge? Was the flora and fauna in Panama before the land bridge closed similar to that in North America, or did it include other elements?”

So far, 10 million cubic meters of earth have been removed from the Canal. The pace of operations is about to accelerate as the Canal Authority awards the final bids for the construction of a third set of locks. More information on the Panama Canal Geology Project is available at striweb.si.edu/jaramillo/current_research/index.html.

Fossils Show Prehistoric Global Warming

John Barrat — Fri, 22 May 2009 12:52:32 +0000

The Past as Prologue
For those who think that global warming is a 21st-century phenomenon, Scott Wing, a scientist at the Smithsonian’s National Museum of Natural History, has news about the past.

Wing headed an international team of scientists whose discovery of plant fossils in the Bighorn Basin of northwestern Wyoming helps document the consequences of a sudden global warming, called the Paleocene-Eocene Thermal Maximum (PETM), 55 million years ago.

Experts believe the PETM, which was caused by a massive release of carbon into the atmosphere, may be an analogue for what is happening today as humans burn increasing amounts of fossil fuel and release large amounts of carbon dioxide.

Plant Movement Signals Global Warming
For nearly 15 years, Wing and his team dug through sediments deposited during uplift of the Rocky Mountains, looking for fossils of the right age and condition. Their discoveries proved that warming caused major shifts in the distribution of plants, allowing southern-dwelling trees and shrubs, related to poinsettia, sumac, and paw-paw, to move some 1,000 miles north in less than 10,000 years. These subtropical invaders flourished for about 100,000 years in what we now know as Wyoming. As carbon dioxide levels dropped and temperatures cooled again, plants related to birches and bald cypress came to dominate the vegetation.

The study and interpretation of this fossil record helps other scientists project future changes in plant life that may result from global warming induced by human activity.