"Beginning in the 1950s we thought that bottle gourds floated across the ocean from Africa," said Logan Kistler, post-doctoral researcher in anthropology, Penn State. "However, a 2005 genetic study of gourds suggested an Asian origin."
Domesticated bottle gourds are ubiquitous around the world in tropical and temperate areas because, while they are edible when young, the mature fruit make ideal lightweight, waterproof, liquid-carrying vessels. They were popular in areas either before development of ceramics or where ceramics never developed.
The 2005 study looked only at targeted sequence markers that turned out not to be informative on the population level, said Kistler. Now we can do sequencing of the large single copy area of the plastid genome, which is about 86,000 base pairs of DNA, he added.
Unlike animals, which have two types of DNA -- nuclear and mitochondrial -- plant cells have three types of DNA -- nuclear, mitochondrial and plastid. Animal mitochondrial DNA is often used in genetic studies because it is completely inherited from the mother and changes very slowly, but in plants, mitochondrial DNA is prone to structural rearrangements, while often carrying a slow mutation rate. The DNA found in plastids such as the organelles that perform photosynthesis and create starch or pigments, is a better choice for plants because it does not recombine, but it mutates fast enough for population-level studies.
The researchers, who report their results in a recent issue of the Proceedings of the National Academy of Sciences, looked at 36 modern samples of bottle gourd and 9 ancient samples. They found that all the ancient bottle gourds from the Americas that were tested fell within the normal variation of the African bottle gourds and not the Asian bottle gourds.
"The best explanation for this is that they came directly from Africa," said Kistler. "However, we wanted to test the possibility that gourds did float from Africa to form New World populations."
Previous studies found that gourds do float in the oceans and that after long periods of time in the ocean they still have viable seeds. The researchers developed an ocean-current drift model that showed that wild African gourds could have simply floated across the Atlantic during the Late Pleistocene. They suggest that large mammals like the mammoth helped naturalized populations establish in the neotropics, because these large mammals were known to eat various members of the family that includes gourds. The seeds are found in ancient deposits of large mammal dung.
Bottle gourds in Africa exist today mostly in the domesticated form, with only small populations of the wild variety in Kenya and Zimbabwe. In the ocean drift model, the researchers looked at realistic, unrealistically conservative and optimistic scenarios. They divided the western coast of Africa by latitude and simulated 12 years of gourd release where one gourd per month entered the ocean in each latitude division. The shortest amount of time it took for a gourd to arrive was 100 days, with an average arrival time of about nine months.
According to the researchers, it is feasible that gourds did float across the Atlantic Ocean frequently. This is especially true of gourds growing near rivers that flow into the ocean.
"It wasn't one gourd that came over and gave rise to all New World gourds," said Kistler. "Populations show up in Florida and Mexico around 10,000 years ago and in Central America a little later."
Also working on this project were Álvaro Montenegro, assistant professor or geography, Ohio State University; Bruce D. Smith, curator of North American archaeology, Smithsonian Institution; John A. Gifford, associate professor of marine affairs and policy; Richard E. Green, assistant professor of biomolecular engineering, University of California Santa Cruz; and Lee A. Newsome, associate professor of archaeological anthropology, Penn State.
The National Science Foundation partially supported this work.
A'ndrea Elyse Messer | EurekAlert!
Sequencing of barley genome achieves new milestone
26.08.2015 | University of California - Riverside
Entomologists sniff out new stink bug to help soybean farmers control damage
25.08.2015 | Texas A&M AgriLife Communications
A University of Oklahoma astrophysicist and his Chinese collaborator have found two supermassive black holes in Markarian 231, the nearest quasar to Earth, using observations from NASA's Hubble Space Telescope.
The discovery of two supermassive black holes--one larger one and a second, smaller one--are evidence of a binary black hole and suggests that supermassive...
A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).
Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...
In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.
These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...
Bacteria do not cease to amaze us with their survival strategies. A research team from the University of Basel's Biozentrum has now discovered how bacteria enter a sleep mode using a so-called FIC toxin. In the current issue of “Cell Reports”, the scientists describe the mechanism of action and also explain why their discovery provides new insights into the evolution of pathogens.
For many poisons there are antidotes which neutralize their toxic effect. Toxin-antitoxin systems in bacteria work in a similar manner: As long as a cell...
It comes when called, bringing care utensils with it and recording how they are used: Fraunhofer IPA is developing an intelligent care cart that provides care staff with physical and informational support in their day-to-day work. The scientists at Fraunhofer IPA have now completed a first prototype. In doing so, they are continuing in their efforts to improve working conditions in the care sector and are developing solutions designed to address the challenges of demographic change.
Technical assistance systems can improve the difficult working conditions in residential nursing homes and hospitals by helping the staff in their work and...
20.08.2015 | Event News
20.08.2015 | Event News
19.08.2015 | Event News
28.08.2015 | Physics and Astronomy
28.08.2015 | Health and Medicine
28.08.2015 | Life Sciences