FUTURE HUMAN EVOLUTION : Can we change human nature?

Humanity's age-old dilemmas are often set down to what we call human nature. Even the most philosophical shake their heads in despair at this, as an impassible boundary to progress. Though some have denied its existence, studies indicate that we do indeed have a nature, instincts, and patterns of behavior which are endemic to our species. Even so... Could we change? In what does our nature consist? Is it hopelessly etched in stone? Or only written on our DNA? If our instincts and behavior have evolved beyond that of earlier primates and hominid ancestors, is it possible for us to improve them? If so, why haven't we done so, noticeably, lately?