Long before humans understood genes, they were selectively breeding animals (like dogs, sheep, etc) and plants to improve desired characteristics. Much of what we eat today on the international plate were crops that were once only grown in specific corners of the world, and which took adaptation, mutation, and extensive breeding to become the number of commercial strains we know today.
Let’s take a look at a few crops, like corn and watermelon, for example.
Here is corn, which not only grew in size but was slowly changed to more readily release its niacin to us directly (otherwise the corn must be nixtamalized in an alkaline solution). Pellagra (a sickness stemming from a lack in niacin) used to be common in areas where the diet was high on corn.
Watermelon also went through a drastic transformation, becoming more watery, more sweet, and increasing in vitamin C.
These crops were creating over thousands of years, with a ramp up of new species in the 20th century through mutagenesis and later (in the late 20th century until now) through targeted genetic engineering. The difference between traditional breeding and genetic engineering can be seen in this diagram:
The number of genes changed, and knowledge of which genes these are, aren’t directly related. Anyone complaining about a lack of regulation for GM, while ignoring the chemical and radioactive mutagenesis used in conventional and organic seed creation, has unfortunately helped contribute to the high regulatory costs for GM that keep only a small number of companies in operation.
Is it good that humans have modified these crops? For us humans, certainly.
We have changed our food to better fit us, to help exclude us from the list of predators the plants were expecting to fight and making their nutrients (like niacin in the case of corn) more available for us to use. Another example is potatoes, which store solanine (which is highly toxic) to help prevent tubers from being eaten. Solanine tastes bitter for us (a lot of poisons do, which is why evolution led to us largely disliking bitter tastes), and selection for sweeter and more delicious potatoes (and better storage conditions) has surely led to a decrease in their solanine content.
So is genetic modification bad? Well, it always depends on what the change is and how it is done.
Is selectively modifying or adding a gene more dangerous than randomly changing genes through radiation? No, and I feel more comfortable knowing exactly what was changed.