The Rhizome of Life

Rhizome

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I stumbled upon an intriguing article, "Life after Darwin," written by the French biologist Didier Raoult and posted on a website titled Project Syndicate. Here's the part that interested me:

All living organisms appear as mosaics of genetic tissue, or chimeras . . . . This framework . . . . resembles a rhizome -- an underground stem that sends out roots and shoots that develop into new plants . . . . [W]e now know that the proportion of genetic sequences on earth that belongs to visible organisms is negligible . . . . Human cells comprise genes of eukaryotic, bacterial, archaean, and viral origin. As this chimerism increases, it occasionally integrates genes from microbes that live within the human body . . . . Once integrated in a person's genome, these genes can be transmitted from parent to child -- making microbial genes their "grandfathers" . . . . [A] transfer of genetic sequences from parasites to hosts could involve hundreds of genes for a bacterium in different hosts. For example, if the bacterium Wolbachia's genes are integrated by different hosts, such as spiders, insects, or worms, the hosts' offspring are also descendants of Wolbachia.

We're all thus genetic chimeras, imaginary creatures of mixed origins that populate the minds of superstitious folk and the tales they tell their children. Just joking. Wrong chimeras. More seriously, I recall discussing such origins of some of our genetic material when I was teaching in Germany 20 years ago, for a biologist in one of my conversation classes brought up the issue in the context of a reading on biogenetically engineered crops. His point was that objecting to biogenetics on the basis of the integrity of an organism's genetic structure is absurd since natural biogenetics is occurring constantly. He then noted that this happens not only in crops but also in humans.

That was the first I'd heard of such a process, and I'd heard nothing since until yesterday. Any experts out there among my readers who might want to post an enlightening comment? What's the extent of this sort of genetic transference? I would expect most of it to be harmful, so how does the body prevent the transferred genetic material from working harm? Especially subsequent generations if the foreign genes manage to insinuate themselves at that level?