As a trivial example, suppose humanity decides to give itself the genes to sense one's orientation and location continuously, like homing pigeons. These oscillations take place on a scale so tiny that sub-atomic particles like protons and neutrons would seem enormous in comparison. Moreover, the intensity of these tiny oscillations is so great that a proton passing by would seem not only large, but insubstantial, like a vast cloud. If so, then some future science may enable us to manipulate aspects of our souls. Scientific naturalism can give only trivial answers to the latter question.
Human is what carries the human genome.
Scientific naturalism will only be able to ascertain our ability to breed with unaltered humans, if there are any left. To the questions of whether and how to preserve our human nature, scientific naturalism gives no answer at all. Scientific naturalism, which is no more than unaided reason, gives knowledge without meaning, technique without teleology. Hence we must turn to faith. We take it on faith that we must preserve and build on our essential human-ness, rather than undermine it.