There was no sudden genetic change in wheat in the 1970s. There have been two key genetic changes at the chromosomal level in the past, with one probably occurring before domestication. The "natural" genetic condition of multicellular plants and animals that reproduce sexually is to have paired chromosomes: organisms like this are called "diploid". Chromosomes are paired, and in normal cell division, each double helix is split into single helixes, which then reform their missing half, becoming double helixes again. When male and female reproductive cells (gametes), the pairs are separated, and each gamete has unpaired chromosomes. When male and female gametes meet, they fuse and each contributes half of each new pair of chromosomes. There are some variants on this usual plant/animal sexual reproduction scheme: sometimes, the gamete just makes a new organism, without combining with another gamete - this organism has unpaired chromosomes, and is "haploid". Sometimes, perhaps because more than two gametes join, or gametes get paired instead of single chromosomes due to some error in cell division, the new organism has chromosome in threes, or larger groups, than pairs. This is much more common in plants than animals. Chromosomes in triples = triploid, chromosomes in groups of 4 = tetraploid, and chromosomes in sizes = hexaploid.

The different species of wheat are quite genetically varied. Some are diploid, many are tetraploid, and some are hexaploid. The wild ancestors of wheat were both tetraploid (wild emmer) and diploid (wild einkorn). Wild emmer is a natural hybrid of two diploid ancestors, one closely related to wild einkorn, and another wild grass. Emmer and einkorn are only minor cultivated varieties today, with common wheat AKA bread wheat dominating. Common wheat is a three-way hybrid, a hexaploid hybrid of three diploid ancestors, via tetraploid emmer as a combination of two of those ancestors (perhaps the ancient Sumerians and Babylonians had some magic insight into the genetics of wheat when they wrote that Gilgamesh was 2/3 god and 1/3 human?). This hybridisation giving hexaploid wheat appears to have happened after the domestication of emmer and einkorn wheat, but happened many thousands of years ago - it is not a product of modern genetic engineering.

Of the other common wheat varieties, durum wheat, the 2nd most grown variety, is tetraploid, spelt is hexaploid, and Persian wheat (Triticum turgidum AKA Triticum turanicum) is tetraploid.

In the later 20th century, many new wheat varieties were developed. These were developed by old-fashioned selective breeding and hybridisation, and some were developed by deliberate mutation by gamma-ray or X-ray or ultraviolet irradiation of seeds. None of these changes had any significant effect on gluten, or the "evilness" or digestibility of wheat.

Some GMO wheat varieties were developed in the 1990s, but not grown commercially. Monsanto sought approval for growing one herbicide-resistant variety, but dropped it when they realised than anti-GMO feelings in the marketplace would badly hurt the export market. In 2020, a GMO drought-resistant wheat was approved for cultivation in Argentina (with Brazilian approval perhaps to follow soon), so GMO wheat might be seen on the market in the near future. These modification still don't affect the gluten or the "evilness" of wheat.

The main source of the "wheat = evil" thing beginning in the 1970s is unrelated to the genetics of wheat. The usual claim is that widespread use of glyphosate herbicides in the 1970s have caused humans to be less tolerant of gluten in their diet. Glyphosate use is related to GMO crops, since Monsanto has developed a wide range of GMO crops that are resistant to glyphosate herbicides, allowing such herbicides to selectively kill weeds growing in the crop. Such GMO crops became common in the 1990s, some decades after glyphosate herbicides became common.

Older wheat varieties still exist, and are grown in places around the world. Large-scale commercial wheat growing is dominated by new varieties, which have been bred/selected for short growing seasons, drought resistance, and other useful traits. These changes haven't affect the gluten. Reverting to old wheat varieties won't help or harm the digestibility of wheat. If the gluten-glyphosate claims are correct, then old wheat varieties will be just as bad as modern wheat varieties.

There are strange pseudo-scientific claims made about gluten and "ancient" wheats vs "modern" wheats. For example, this website claims that:

Remember that all wheat contains gluten, and gluten consists of two proteins:

gliadin (which causes the rise)

glutenin (which causes elasticity)

Most individuals with gluten issues react negatively to the gliadin.

Einkorn has a higher ratio of gliadin to glutenin, so naturally we would think that it would be far worse for individuals with gluten sensitivities than modern wheat. However, because Einkorn is not hybridized, the original DNA structure remains intact and actually helps the body to digest these gluten proteins properly.

This makes no sense. Even if "the original DNA structure remains intact", it will not help the body digest these proteins. Further, if the "gluten + glyphosate = evil" claims are to be believed, it's all about the glyphosate in the environment and our diet, and not whether the wheat is diploid or hexaploid.

Certainly, some people have trouble digesting gluten (and some people have worse reactions, such a coeliac disease). Some people report less reaction to einkorn that common wheat. We don't know why. I don't know if proper double-blind studies have been conducted on this, and therefore I don't know whether we can rule out placebo effects as a major contributor. Food allergies and intolerances are only poorly understood, and it's quite possible that the switch from one type of wheat to another in the diet (e.g., from common wheat to einkorn) helps, but that the change is due to components other than the gluten.

At this point, we pass from the history of wheat varieties and wheat genetics, and a brief look at the history of gluten "conspiracy theories", to where science might be more useful, and since this is a history sub, I'll stop and leave some references for further reading on the science if you are interested:

• Elli, L., Roncoroni, L., & Bardella, M. T. (2015). Non-celiac gluten sensitivity: Time for sifting the grain. World journal of gastroenterology, 21(27), 8221–8226. https://doi.org/10.3748/wjg.v21.i27.8221

• Geisslitz, S., Longin, C., Scherf, K. A., & Koehler, P. (2019). Comparative Study on Gluten Protein Composition of Ancient (Einkorn, Emmer and Spelt) and Modern Wheat Species (Durum and Common Wheat). Foods (Basel, Switzerland), 8(9), 409. https://doi.org/10.3390/foods8090409