What do you mean by 'human nature'? It seems like 'nature' is in general ill-defined in the first place. If you mean simply, "what it's like to be a human" then I think in many relevant ways we're changing that all the time.

You can change it in 5 minutes with an icepick.

Modafinil removes the urge to sleep pretty well - but as thomblake mentions, it depends on how you define that ill-defined concept.

There is no ability to change human nature as yet.

If you re-read the comment you're replying to, you'll see I was answering the part about "your own nature", not "human nature".

However, if you consider that most of what constitutes "human nature" is actually metaprogramming that drives the acquisition of our individual nature, then an enormous part of that nature is not actually hard-wired.

People who've not done any significant amount of mindhacking are horribly biased towards believing that aspects of their individual nature are in fact universal. (Actually, everyone is so biased, it's just that non-mindhackers are an order of magnitude worse, because they don't have the experience yet of seeing the consistent disconnect between their automatic thoughts and external reality.)

Stupid example: earlier this week I realized that I was choosing not to aggressively pursue certain goals because I felt the "rush" to complete them would be stressful. Then I realized that there was no intrinsic association between "rush" and "stress" -- that was a learned response, and a fairly specific one at that. (My mother always freaked out whenever she was late... which was virtually all the time.)

However, until I thought to question that specific assumption, I was not conscious of it being my individual nature - it was assumed to be part of human nature, or just the nature of the world itself. (i.e. "of course it's stressful to rush")

It's impractical to question every implicit association, though, and practical knowledge/experience is needed as a guide to know what assumptions to surface and question. (A good rule of thumb, though, is that anything that provokes a negative emotional reaction should be questioned thoroughly.)

For the individual at least. Eugenics of course gives the ability to change human nature (albeit with a time scale and logistical difficulties that make it useless to most purposes).