Gene jumping: by contact!

Graft a branch of one plant onto another, and at the contact point at minimum chloroplast genes can move from one to the other, even if they are different species.

I remember wondering as a lad, rather innocent of the details of agriculture, if it were possible to somehow mix sugarcane and lime trees so that the fruit would provide pre-sweetened lime juice. I discovered later how silly that was, but apparently there can be some transfers anyway. Although the gene mix might result in sour woody stalks instead of sweet fruit...

Hmm. "You are what you eat." Our bodies are quite good at digestion and most of our food is thoroughly broken down, but we have gut bacteria that seem to play unexpected roles outside the gut thanks to chemical cues, we have skin in contact with thousands more kinds and with the occasional ornaments and perforations, and maybe some of that food makes contact for long enough to gene-jump.

How much of our environment changes us?

One of the symbols in The Pilgrim's Regress by Lewis was of an addictive plant that the tenants grafted into everything they could find. Everything was more or less tainted, and the only way to avoid the worst-tainted foods was with a complicated dietary scheme.

I don't want to go there. I like Twain's "eat what you like and let the food fight it out inside."