May of these don't seem like binary adjustments, though. Perhaps you can increase the tolerance to radiation, but how? Perhaps by causing the body to produc

May of these don't seem like binary adjustments, though. Perhaps you can increase the tolerance to radiation, but how? Perhaps by causing the body to produce a protein that shields cells from these effects, much like melanin does for UV. Assuming you do this, you immediately have to ask, what other effects does that have on the body? When these cells are destroyed by radiation, what are their breakdown products? How quickly can the body replenish them? What new nutritional requirements will be necessary to support them? The same questions can be raised for any of these "DNA feature flags." It seems to me, viewed a certain way, the human body is almost entirely driven by emergent phenomenon. I have serious doubts about our ability to edit the source code to achieve very straight-forward single side-effect modifications. We may very well be limited to merely adjusting "errant" DNA sequences that cause or are implicated in disease or undesired attributes. Who would choose a short child? Or one with myopia? Or one with weak muscles? Or even one with the misshapen chest and facial orifices necessary to survive lower partial pressures of oxygen? The long term effect of custom genetic modification actually seems like it would just be used to reduce the overall genetic diversity of humans on the whole, not to improve it in drastic ways.