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We are slowly working on replacing our popular Flash-based content and will update this content as it becomes available. If you would like to help us as we work on these updates, please consider donating here. The history of modern-day maize begins at the dawn of human agriculture, about 10, years ago. Ancient farmers in what is now Mexico took the first steps in domesticating maize when they simply chose which kernels seeds to plant.
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These farmers noticed that not all plants were the same. Some plants may have grown larger than others, or maybe some kernels tasted better or were easier to grind. The farmers saved kernels from plants with desirable characteristics and planted them for the next season's harvest. This process is known as selective breeding or artificial selection. Maize cobs became larger over time, with more rows of kernels, eventually taking on the form of modern maize.
The identity of maize's wild ancestor remained a mystery for many decades. While other grains such as wheat and rice have obvious wild relatives, there is no wild plant that looks like maize, with soft, starchy kernels arranged along a cob. The abrupt appearance of maize in the archaeological record baffled scientists. Evolution was generally thought to occur gradually through minor changes.
Why did maize appear so suddenly? Maize cobs uncovered by archaeologists show the evolution of modern maize over thousands of years of selective breeding.
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Even the oldest archaeological samples bear an unmistakable resemblance to modern maize. All Rights Reserved. Through the study of genetics, we know today that corn's wild ancestor is a grass called teosinte. Teosinte doesn't look much like maize, especially when you compare its kernals to those of corn. But at the DNA level, the two are surprisingly alike. They have the same number of chromosomes and a remarkably similar arrangement of genes. In fact, teosinte can cross-breed with modern maize varieties to form maize-teosinte hybrids that can go on to reproduce naturally.
Scientists study teosinte-maize hybrids and their offspring through the process of genetic archaeology. This process helps geneticists understand what is happening at the DNA level to make teosinte and maize so different. By combining clues from genetics and the archaeological record, scientists have pieced together much of the story of maize evolution. One of the first scientists to fully appreciate the close relationship between teosinte and maize was George Beadle.
In the s, Beadle studied teosinte-maize hybrids and showed that their chromosomes are highly compatible.
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Later, he produced large numbers of teosinte-corn hybrids and observed the characteristics of their offspring. By applying basic laws of genetic inheritance, Beadle calculated that only about 5 genes were responsible for the most-notable differences between teosinte and a primitive strain of maize. Using more-modern techniques, another group of scientists analyzed the DNA from teosinte-maize offspring. They too noticed that about 5 regions of the genome which could be single genes or groups of genes seemed to be controlling the most-significant differences between teosinte and maize.
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In recent years, geneticists have used advanced molecular-biology tools to pinpoint the roles of some of the genes with large effects, as well as many other regions across the genome that have had subtle effects on maize domestication. The earliest events in maize domestication likely involved small changes to single genes with dramatic effects.
We know the events were early because there is little variation in these genes between maize varieties, suggesting that modern varieties are descended from a single ancestor. So could a sudden shadow falling over their leaves. Instead, plants appear to have developed intricate stress defence systems to sense their environment and help them detect danger and respond appropriately," says Van Aken.
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Importantly, the study also identified two proteins that could switch off the plant's touch response. In the future, this could help plants in controlled environments, such as greenhouses, from changing their genes and responding to 'false alarm' stimuli.
One study on its own obviously isn't enough to overhaul our understanding of plant stimulation perception, and more research is needed to replicate the finds. But for now, maybe we should all be more thoughtful when we're prodding and poking our plants, or blocking their light with our giant human heads. The good news? Singing seems to be pretty safe.
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