"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!
Plasma-zapping process could yield trans fat-free soybean oil product
02.12.2016 | Purdue University
New findings about the deformed wing virus, a major factor in honey bee colony mortality
11.11.2016 | Veterinärmedizinische Universität Wien
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Materials Sciences
08.12.2016 | Materials Sciences
08.12.2016 | Physics and Astronomy