An per your question: the same that qualifies you or me, which is being alive and capable of observe and extrapolate possible outcomes through thinking.
Unless in possession of a crystal ball, nobody can say what is bound to happen to our species as climate changes take place.
Like any other species we are vulnerable to extinction but as many physicist have underlined, the highest risk for a civilization is its start. After a certain point is achieved, a civilization can become technically immortal.
If we are to go back far enough, we are bound to find an ancestor mostly herbivore. On that level, going for the scenario I mentioned would have been some event.
Selective breeding increases the frequency of a given set of genes, already present in a species, in order to better manifest specific, more advantageous - either nature or human chosen - traits.
Random mutations can occur when biological reproduction happens but unless extreme and radical - which often prove fatal for the offspring - are not relevant for the species in the immediate.
These principles are applicable to both plants and animals.
Now grafting takes a part of one plant - usually a small branch - uses another plant to provide the root system - usually something that grows much faster than the graft - and this process multiplies asexually the plant from which the branch was oroginally cut. No genes are carried over between the two plants.
This is valid to get a bunch of trees out of a single one in a very short time but it will not introduce new genes into the crop.
Quince trees are often used as root stock to graft other trees, like pear and apple. If the seeds from those grafted trees were to be sprouted, planted and nurtured to maturity, apples or pears would grow but of completely new varieties. The quince trees used to provide the root for grafting would provide zero genes to the new varieties.
Can you expand on why you consider grafting as a tool for genetic manipulation?
Our ancestors were primarily leaf eaters, so moving to grass wouldn’t be that unusual. But let’s picture the first proto-human that decided to go for the carcass of another animal, either killed by a predator or by fire or lightning. That would have been an event.
Last time I was taught about biology, selective breeding was a process through which, over a long period of time, individuals with favorable traits were multiplied in order to increase the prevalence of such traits.
The genes were already introduced, hence, no modification. Already existing characteristics were allowed to further express and refine.
Genetic modification, to my understanding, implies introducing genetic information into the genome of an organism to produce another with traits previously completely absent in the species.
Selection vs manipulation.
I’ll concede there are a few cases where the lines blurr, like the golden rice, where a gene that codified the production of vitamin A in the grain was/is already inactive or so receassive, in order to have it express again would require gene manipulation but I think a selective production program was put forward in an attempt to bring out that gene again.
Like many other cultures, bananas and apples were selectively reproduced to obtain fruits with more to eat. Corn, carrots, every single kale and cabbage, potatoes, oranges and even strawberries can go into this basket.
The wild banana has almost nothing to eat, being filled with large seeds and we can still find wild apples, by nature very tart but still edible. Every single cereal we plant and harvest today was originally nothing more than a wild grass.
But to call the work of millenia and who knows how many generations of farmers genetic modifications is a bit over the top.
GMOs are very recent introductions and normally for obtaining pest, drought or disease (more) resistant plants.