A grass called teosinte is thought to be the ancestor of corn, but it doesn’t look much like corn at all. Smithsonian scientists were surprised to find that teosinte planted in growth chambers under climate conditions that simulate the environment 10-12,000 years ago looks more like corn. This may help to explain why early farmers chose to cultivate teosinte and lends support to the idea that teosinte was domesticated to become one of the most important staple crops in the world.
By simulating the environment when corn was first exploited by people and then domesticated, Smithsonian scientists discovered that corn’s ancestor, a wild grass called teosinte, may have looked very different then than it does today. The fact that it looks more like corn under these conditions may help to explain how teosinte came to be selected by early farmers who turned it into one of the most important staple crops in the world.
The vegetative and flowering structures of modern teosinte are very different from those of corn. These and other differences led to a century-long dispute as to whether teosinte could really be the ancestor of corn.
“We grew teosinte in the conditions that it encountered 10,000 years ago during the early Holocene period: temperatures 2–3 degrees Celsius cooler than today’s with atmospheric carbon dioxide levels at around 260 parts per million,” said Dolores Piperno, senior scientist and curator of archaeobotany and South American archaeology at the Smithsonian’s National Museum of Natural History and the Smithsonian Tropical Research Institute, who led the project. “Intriguingly, the teosinte plants grown under past conditions exhibit characteristics more like corn: a single main stem topped by a single tassel, a few, very short branches tipped by female ears and synchronous seed maturation.
After the Industrial Revolution, carbon dioxide rose to today’s 405 parts per million, the level in the control chamber where teosinte plants look like plants in the wild today—tall, with many long branches tipped by tassels and seed maturation taking place over a period of a few months. Co-author Klaus Winter usually studies the effects of rising atmospheric carbon dioxide levels on tropical plants as a senior staff scientist at STRI. Piperno and Winter devised a scheme to essentially travel back in time by comparing plants grown in modern conditions with plants grown in the early Holocene chamber.
“Now it appears to be an open question when in the Holocene teosinte became the plant very distinctive from maize in vegetative architecture and inflorescence sexuality that we see today and use as the baseline for research on maize domestication,” said Piperno. “When humans first began to cultivate teosinte about 10,000 years ago, it was probably more maize-like—naturally exhibiting some characteristics previously thought to result from human selection and domestication. The environment may have played a significant, if serendipitous, role in the transition through inducing phenotypic plasticity that gave early farmers a head start.”
Phenotypic plasticity is an organism’s ability to change in response to the environment, causing genetically identical organisms to look very different when they live in different conditions. As they formulate a “new modern evolutionary synthesis,” in part with concepts that Darwin could not have known of, evolutionary biologists continue to debate the importance of the environment and plasticity on evolutionary change and the origins of the diverse forms of life on Earth today. However, new evidence shows that these environmental–phenotypic interactions are in a growing number of organisms. This is one of the first studies to examine the influence of these processes on plant domestication.
“Extending these concepts to domestication research allows anthropologists to become more fully engaged in modern evolutionary theory and practice,” Piperno said.
The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a unit of the Smithsonian Institution. The Institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Website: www.stri.si.edu.
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SI-25-2014
Piperno, D.R., et al., Teosinte before domestication: Experimental study of growth and phenotypic variability in Late Pleistocene and early Holocene environments. Quaternary International (2014). http://www.sciencedirect.com/science/article/pii/S104061821300983X
The PR is from The Smithsonian
I have to wonder though, where they get this info: “After the Industrial Revolution, carbon dioxide rose to today’s 405 parts per million”.
Last I checked, today, MLO was still below 400 ppm:
397.82 parts per million (ppm) CO2 in air 02-Feb-2014 http://t.co/5Q2FLbb4ix
— Keeling_Curve (@Keeling_curve) February 3, 2014
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“These and other differences led to a century-long dispute as to whether teosinte could really be the ancestor of corn.”
The estimate of 260 ppm for 10,000 years ago isn’t much change to the 280 ppm of a century ago so the reference to 405 ppm (local estimate?) seems to be a mis-direction. Note the text claims the argument started an imprecise century ago.
Another hypothesis is that there was a plant that mutated (an early GM candidate) and was selected because of its better traits. In botany, especially tree fruits, say apples, these new types are called sports.
Did anyone think to try to pop the Teosinte grain?
“We grew teosinte in the conditions that it encountered 10,000 years ago during the early Holocene period…:
————
I hope nobody tries to make a joke about corn-holocene!
Sounds like more CO2 is beneficial to food production.
Phenotypic plasticity is an organism’s ability to change in response to the environment, causing genetically identical organisms to look very different when they live in different conditions.
So … what is the genetic similarity of corn to teosinte?
.
Perhaps temperature and CO2 levels are not dependent variables. That is to say, it seems possible that a Holocene Chamber with 260 ppm CO2 and no temperature adjustment would likely produce the same result.
Although corn was first domesticated in Mesoamerica, 300 miles of travel in either polar direction would produce the same 2-3 degree C temperature change.
The ability of a population to evolve is an evolved trait as is phenotype plasticity. It should be no surprise that they are related. BTW, the public school version of the theory of evolution is designed primarily as a mechanism to denigrate Christianity. It is about as close to the real thing as is the mischaracterization of Christian belief that public school teachers use in contrast.
A populations evolutionary trajectory is in the direction that maximizes the ability of the population to produce offspring that live long enough to produce offspring. Therefore Dr. Flying Spaghetti Monster is a fraud.
Google is our friend, as usual, but this is one of the best starting points corn-teosinte comparison:
http://learn.genetics.utah.edu/content/selection/corn/
For a shortcut to genomics,
http://www.nature.com/ng/journal/v44/n7/full/ng.2309.html?WT.ec_id=NG-201207
(“Comparative population genomics of maize domestication and improvement”, Matthew B Hufford et al., may be paywalled)
Have there been studies that show carbon dioxide concentrations in the atmosphere 10 thousand years ago in regions where teosinte grew? The 260 ppm is from polar ice core data. Last I heard, our ancestors weren’t doing much farming in Antarctica or Greenland back then.
Interesting but not convincing, since early mesoAmericans lived in a variety of microclimates given the mountainous nature of the region, so temperature and CO2 need to be teased apart. But this is certainly an extreme example of the new concept of phenotypical plasticity (originating in what 20 years ago was though to be junk DNA, but which we know know at least partly controls gene expression). Another vivid example of the science is not settled…
The devil is in the details. The exact quote was “Intriguingly, the teosinte plants grown under past conditions exhibit characteristics more like corn: a single main stem topped by a single tassel, a few, very short branches tipped by female ears and synchronous seed maturation”.
This means that all of those things must be present. This being the first time I was ever interested in this plant, I searched the net for real-world pictures, not the wikipedia pictures that are everywhere. If you look at Teosinte grown in Colorado (slightly colder, slightly less CO2 because of altitude), you get a single main stem, very few short branches with female ears, but multiple tassels. See http://keen101.wordpress.com/2011/10/21/growing-prehistoric-corn-teosinte/ for examples. He has a photobucket list of photos.
That looks enough like corn to get a meager harvest, but it doesn’t have a single tassel and who knows about sychronous maturation. I’m just saying that if these plants are grown in cold mountain conditions today, shouldn’t that also simulate conditions 10k yrs ago? Are there naturally occuring growing conditions today that give teosinte a single tassel? I’m betting the Smithsonian didn’t ask that question with too much enthusiasm.
As an interesting discovery because of this story, I found that there are a few people on the net documenting their gardens of teosinte crossing with corn and indian corn. Who knew that was a hobby?
JDN says:
Every possible occupation is certain to be exercised by somebody as a hobby. In agricultural selection, crossing a promising cultivar with a wild type to kick it out of a dead end or an undesired local optimum is almost a knee-jerk reaction. Got larger fruits? Good. Roots not viable in the field? Need another cross.
I’ve been involved with the preservation of a specific Native American corn variety for years. It is not unusual for occasional plants to revert to some ancient variety which bears little resemblance to modern “corn”.
The paper doesn’t make sense. About 10,000 years ago, at the beginnning of the Holocene, the temperatures were higher, not lower than todays. It be interesting to see the behavior of teosinte under actual holocene conditions.
Maybe it’s just my memory playing tricks on me, but I’d swear that I’ve seen plants resembling teosinte growing in fallow cornfields. Could it be that a seed from a modern hybrid plant would revert to phenotypes more closely resembling teosinte if it lies in the ground all winter and is allowed to sprout and grow in an uncrowded environment?
LeeHarvey: Does your memory of plants resembling teosinte relate to one of these regions?
http://www.maizegenetics.net/taxonomy
Wiki says (http://en.wikipedia.org/wiki/Zea_(genus)#Origin_of_maize_and_interaction_with_teosintes):
“All but the Nicaraguan species of teosinte may grow in or very near corn fields, providing opportunities for introgression between teosinte and maize.”
All wild types of maize appear to be niche-specific, even within their native range. That is fortunate for us. Corn would be rather more expensive if its wild relatives were more broadly adapted.
More details on teosinte distribution here:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047659
docstephens says:
February 3, 2014 at 9:58 am
“Have there been studies that show carbon dioxide concentrations in the atmosphere 10 thousand years ago in regions where teosinte grew? The 260 ppm is from polar ice core data.”
———————
Tes, studies of fossil plant stomata, … to wit:
“Data from various stomata studies (ref. 10-20) show CO2 concentrations over the last 11,000 years varied between 260 and 340 ppm (average: 305 ppm). In contrast, the Dome C ice core record shows no significant variability and considerably lower overall CO2 levels (average: 270 ppm).” http://www.geocraft.com/WVFossils/stomata.html
10,00 years ago it was warmer than today with an attendant CO2 spike that would have been much higher than 400ppm. See what those conditions do for teosinte.
_Jim says: @ur momisugly February 3, 2014 at 9:37 am
So … what is the genetic similarity of corn to teosinte?
>>>>>>>>>>>>>>
That was my first thought.
If they can figure out how many descendants Genghis Khan has and 1 to 4% of non-African modern human DNA is shared with Neanderthals, you would think they could figure out if teosinte is an ancestor to corn and what the genetic differences are.
I am not up on genetics but if I recall what I read correctly, the number of mutations can give a pretty good idea of when a branching occurred.
LeeHarvey says: @ur momisugly February 3, 2014 at 11:00 am
Maybe it’s just my memory playing tricks on me, but I’d swear that I’ve seen plants resembling teosinte growing in fallow cornfields….
>>>>>>>>>>>>>>>
The pure bred parents of modern hybrid seed corn are pretty anemic looking scraggly messes you would have a hard time identifying as modern corn. You are probably seeing reversion towards the pure breds. (Ex husband worked for a seed corn company during Vietnam era)
@Gene Selkov –
Nope… never been south of Monterrey, and I don’t ever recall seeing a cornfield up close in Mexico. I was thinking specifically of fields in Iowa.
@Gail Combs –
I think you may have pegged what I was seeing.
Interesting paper on the origins of zea mays here:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC122905/
Not paywalled.
The more problematic issue is 10ky New World agriculture–I think that’s still a minority position, about 4ky too early by the majority, especially for corn. –AGF
Not only did they get the current ppm levels wrong, but they seem to be unaware that levels of CO2 didn’t start to take off until about mid century last century, not at the start of the industrial revolution.
agfosterjr said @ur momisugly February 3, 2014 at 2:32 pm
The paper I referenced above says:
Close enough to 10kya. The continuation of Mexican maize required human intervention. Maize doesn’t self-sow.
American corn/maize is a genetic expression that must be selected for continually. While it does self sow or regrow from seed that falls to the ground, the genetic expression drifts do to stress from environmental causes. Modern varieties are mostly hybrid and cannot accurately recreate themselves. Old straight bred lines are somewhat flaky and still must be rouged of undesirables to get the best expression in the next generation of the characteristic desired. Without constant selection corn/maize will revert to grass after a number of generations. On the other hand its’ very rich double dose of genes gives it an extreme range of possibilities for GMO design. Corn/maize is grown in every environment that can be farmed, from Alaska to Chile. Not bad for a subtropical grass.
This guy can’t even get the CO2 content of the atmosphere correct. I’m not sure I would give too much credence to the rest of his assertions. 😉 pg
Whether those researchers are right or wrong and I suspect they are partly wrong in their conclusions, spare a thought for those guys and gals, those unrecognised researchers who have tramped and travelled endless kilometres over the past 6 decades in some of the most inhospitable regions on earth to try and find those often quite small natural remnants of the old and original plant species that are the very foundation today of mankind’s and his domesticated animal’s food supplies.
Spare a thought for the laboratory staffs who both analyse both the potential food characteristics of those old species as well as the outcomes of their crosses that provide us with most of our major food supplies today,
Spare a thought for the plant geneticists, few in number across the world, who put together the appropiate genes from a whole range of varieties and species to pass onto the plant breeders.
And spare a thought for the plant breeders, those highly dedicated but globally small in number, group of men and women who when they begin their careers after gaining employment as a plant breeder may not see any commercially acceptable outcomes for their plant breeding efforts for perhaps some dozen or often more years.
It takes ten to fifteen years to produce a new and improved variety of wheat and much, much longer than that, a couple of decades for improved fruit trees and many other similar fruiting food plant species.
Without those plant breeding researchers, most of them highly dedicated, they have to be dedicated as they are usually paid a lot less for their essential to humanity’s food plant breeding efforts than most so called climate scientists, a large percentage of mankind’s numbers, possibly as many as three quarters of mankind’s present day numbers would starve or be killed in the ensuring breakdown of society if a major global food shortage developed.
It can still happen as with the UG99 rust of a few years ago which wiped out wheat varieties in
Africa and the middle east that were not resistant to that strain of rust which very few of all currently grown varieties of wheat are.
The geneticists and breeders moved fast in an international effort to find resistance to UG99 in other varieties and in those ancient plant species and to transfer that resistance to new varieties to counter the UG99 rust fungus.
Each and every one of those plant food researchers and plant breeders and the work they do, the real actual results of which each of us can eat our fill of food each day, every day, and that for all 7 billions of our numbers, are worth some many hundreds of so called climate scientists in their importance to mankind and mankind’s future.
Climate scientists have produced nothing of lasting or even short term value to humanity.
Plant breeders feed the world, all seven billions of us and an even larger number of the animals upon which humanity depends for food, transport and pleasure.
Without those food researchers and plant breeders, most of future humanity will eventually starve.
Without today’s version of climate scientists the world would be much richer, far less traumatized by groundless and baseless climate scientist’s deliberately generated fears and far more socially cohesive.
And science itself would still be a profession that would still be admired and respected.