Human-Assisted Evolution is still Natural Evolution
I would like to raise a discussion - a necessary (in fact key) component of 'natural selection' or 'natural evolution' is one upon which I am not sure how many will agree with me, that of defining the 'natural cause, driver and vehicle' of biological evolution. There have been popular suggestions recently (in fact, it is almost a 'natural' assumption to make at present) that humans are reaching the technological stage where they will be able to 'take over' (or hijack) the role to evolve from nature, because humans via the human endeavours of medical science are now able to 'evolve themselves'; an interesting point in itself, perhaps for the first time humans can truly evolve 'by design'.
However I would argue that ANYTHING humans do is by term 'natural', as humans are in fact natural. Just as termites build a home that will alter their physiology over time as a result, so do humans alter many facets of their internal (biological) and external (environmental) elements. If humans change a gene consciously via medical alteration, this is still a 'natural' event - the only way it could be considered otherwise is if (a) humans were not from Earth (b) humans are exempt from the usual rules of physics (c) humans are able to defy nature. None of the above statements are true, so all human acts are natural acts; if we 'evolve' by our own hand, this is still evolution, in fact maybe even a pacier evolution. Of course, human-assisted-evolution may not lead purely to advances as humans largely anticipate, but may lead to the hits/misses that 'natural selection' as we commonly interpret it also experiences.
It is illogical, I believe, for humans to formally separate the natural vs the 'man-made', we too are all 'natural', thus all our actions, causes, results etc are natural too - it is only at this stage in time that our actions/results have far broader reaches than animals of other species.
We are natural, and our actions and their results are all natural by definition, we only pretend they are not otherwise, for the fact that to us our modern actions look sophisticated. Though perhaps to beings from millions of years from now, our actions will seem as low-tech as termite mounds, and they will track our evolution through these days until then, and notice how we had some play in our own evolution. But this is still natural. To say otherwise would disqualify the action of any creature on this earth as 'natural', rendering any conscious/instinctive act of any creature as 'unnatural'. The level of sophistication of the action is irrelevant.