Those are all good questions and I can't answer them.  I am familiar with the "landrace" variety of seeds from that National Geographic magazine.  From searching the Internet I would make a guess that "heirloom" seed is seed that is unmodified, old seed, that has been used for many decades.  I do know that landrace seeds are seeds found in the wild or ancient farming, that have never been modified from their wild state.  What makes the landrace seeds so good is that because they have been propagated by nature, they have lived through all sorts of disease and have a built in resistance to disease, even drought and other things.   

Wheat is a grass, and from what little I know about it the landrace varieties are significantly smaller and less productive than hybrids.  Keep in mind that these farmers are in direct competition with their neighbors, the changes in the markets, the weather, and the government subsidy programs.  Those that I worked for could either have good years or bad years depending on a lot of factors.  These individual farmers are out to maximize their production any way possible, and I can't blame them.  Of the three I worked for more than 50 years ago, all of them went out of business because they couldn't ride out the bad years along with the peak years.  It is not an easy life and requires a tremendous capital investment for machinery, seed, fertilizer, and of course land.  During my first year in harvest I would guess that the average yield of wheat was 20-24 bushels per acre.  During my last year there the yield was up to about 32-35 bushels per acre.  This was dry land farming.  They increased the yield through new hybrid seed and, fertilizer - chemical fertilizer.  Both paid big returns.  Now in the Columbia Basin project where they irrigate and can raise crops every year, the last I heard they were able to get between 150 to 180 bushels per acre.  However, the Columbia Basin farm size is limited by government control (two 160 acre plots, I believe) so in theory a corporation can't come in and buy lots of land and monopolize it. 

I don't know anything about vegetables other than potatoes.  Potatoes originated in the Andes, spread to both Europe and North American and from what I know have probably remained more unchanged than any other veggie.  Other than that, I know nothing about the origins of vegetables, except perhaps the pepper.  They still find new varieties of peppers in the wild. 

Its an interesting field.

seedsavers has a bank of heirloom seeds that is both saves and sells. is that the same thing as the landrace seeds you mentiioned above?

also, what is landrace wheat like? you said landrace corn is small and would be unprofitable for large scale farming. does the same hold true for landrace wheat?

also, some actually make the argument that some modern vegetables like carrots are not "real food" because they are highly hybridized and altered versions of food that don't grow anywhere in nature. is there such a thing as landrace versions of common garden vegetables like carrots?

thanks for any input, i appreciate an experienced voice.

Here is a story of a wheat from ancient Egypt which produces a high quality without artificial fertilizers and pesticides.  It's but one reason we have to continue to search for old seeds.

Kamut®: Ancient Grain, New Cereal

Robert M. Quinn

Kamut® is a registered trademark of Kamut International, Ltd., used in marketing products made with a remarkable grain. The new cereal is an ancient relative of modern durum wheat, two to three times the size of common wheat with 20–40% more protein, higher in lipids, amino acids, vitamins and minerals, and a "sweet" alternative for all products that now use common wheat (Fig. 1). Nutritionally superior, it can be substituted for common wheat with great success. Kamut brand wheat has a rich, buttery flavor, and is easily digested. A hard amber spring type wheat with a huge humped back kernel, this grain is "untouched" by modern plant breeding programs which appear to have sacrificed flavor and nutrition for higher yields dependent upon large amounts of synthetic agricultural inputs.

Fig 1. Kamut® wheat.

Although the Kamut brand wheat is thousands of years old, it is a new addition to North American grain productions. It's origins are intriguing. Following WWII, a US airman claimed to have taken a handful of this grain from a stone box in a tomb near Dashare, Egypt. Thirty-six kernels of the grain were given to a friend who mailed them to his father, a Montana wheat farmer. The farmer planted and harvested a small crop and displayed the grain as a novelty at the local fair. Believing the legend that the giant grain kernels were taken from an Egyptian tomb, the grain was dubbed "King Tut's Wheat." But soon the novelty wore off and this ancient grain was all but forgotten. In 1977, one remaining jar of "King Tut's Wheat" was obtained by T. Mack Quinn, another Montana wheat farmer, who with his son Bob, an agricultural scientist and plant biochemist soon perceived the value of this unique grain. They spent the next decade propagating the humped-backed kernels originally selected from the small jar. Their research revealed that wheats of this type originated in the fertile crescent area which runs from Egypt to the Tigris-Euphrates valley. The Quinns coined the trade name "Kamut" an ancient Egyptian word for wheat. Egyptologists claim the root meaning of Kamut is "Soul of the Earth."

In 1990, the USDA recognized the grain as a protected variety officially named 'QK-77'. The Quinns also registered Kamut as a trademark. Perhaps the most significant aspect of the introduction and cultivation of Kamut brand wheat is that it is an important new crop for sustainable agriculture. This grain's ability to produce high quality without artificial fertilizers and pesticides make it an excellent crop for organic farming.

The real history of the Kamut brand grain has been as elusive as its taxonomic classification. Although not thought to have been in commercial production anywhere in the world in the recent past, most scientists believe it probably survived the years as an obscure grain kept alive by the diversity of crops common to small peasant farmers perhaps in Egypt or Asia Minor*. It is thought to have evolved contemporary with the free-threshing tetraploid wheats. Scientists from the United States, Canada, Italy, Israel, and Russia have all examined the grain and have reached different conclusions regarding its identification. All agree that it is a Triticum turgidum (AABB) which also includes the closely related durum wheat. The correct subspecies is in dispute. It was originally identified as polonicum. Some now believe it is turanicum, while others claim it is durum. One Russian scientist believes it is a durum cultivar called 'Egiptianka' or "the durum of Egypt." Still others believe it is may evolve from a mixture of many types which would be consistent with its supposed descent from an ancient landrace originally gathered by primitive farmers from the wild. The majority now identify the grain as turanicum commonly called Khorasan wheat. Although its true history and taxonomy may be disputed, what is not disputed is its great taste, texture, and nutritional qualities as well as its hypo-allergenic properties.