One of the most optimistic - perhaps excessively optimistic - philosophies that take shelter under the umbrella terms of atheism and humanism is transhumanism. Transhumanism is a set of loosely associated philosophies which all share a belief in the desirability of transcending the biology of the human condition through technology.
At the marginally more plausible end of the scale, this may entail feats of technology such as preserving the terminally ill by cryogenically freezing their bodies, to be thawed out in a future age once a cure is discovered; or the invention of genetic or other treatments that arrest or reverse the aging process, allowing people to live greatly extended lives. On the far more enthusiastic end of the scale, other transhumanist ideas include nanotechnology that can repair or reconstruct the human body from the inside, or the ability to digitally scan and simulate our brains to create robot doubles that would think, believe and act just like the originals. (Whether these "uploaded" beings would be the originals is a matter of considerably more debate.)
Of course, none of these wonders are presently possible. At the moment, even the most modest transhumanist ideas are little more than pipe dreams. On the other hand, the accelerating growth of technology has already allowed us to transform the human body in ways that previous eras would have found inconceivable. We can already transplant limbs and organs from one person to another, or in some cases, replace them with mechanical duplicates. We have nascent technologies that can read brainwaves or the firing of neurons and transform them into robotic action. Our ability to treat disease through genetic therapy is still rudimentary, but there can be little doubt that it will improve. In the far future, some of the transhumanist dreams may be possible. What should our response be to this kind of technology?
The first thing I have to say is that, even if these ideas become possible in the future, there are more basic problems we should confront first. As long as human beings still suffer from poverty, malnutrition and treatable disease, we should concentrate on eradicating those. It's already an injustice that some people have access to vastly better medical care than others because of the circumstances of their birth. It would be a far greater injustice if rich people of the First World had access to life-extending innovations while others still suffer needlessly from easily curable diseases. Before we start work on raising the human baseline, in my opinion, we should ensure that everyone is lifted up to that baseline.
But if this could be done, other problems would soon follow. If human beings could live forever, then we would inevitably face a severe problem of overpopulation, since all life, of whatever form, must consume resources. The Earth is only so big, and the natural resources we can tap, however carefully managed, are finite. It seems the physics of our universe conspire to prevent interstellar travel on any large scale, and although it's conceivable that those limits will be circumvented, we can't just assume that this will be the case. If this is so, then it might be argued that humans have a duty to die - at the very least, to cease life-extending treatments after a certain period and allow natural aging to resume.
The last issue concerns the "uploading" of human minds into software. While I find this idea almost too strange to countenance, there's nothing about it that's physically impossible. If it were ever feasible, it would raise deep questions about the nature of personal identity, which I hardly feel qualified to address. But, I have to point out, it could not create two identical individuals - at least not for long. If an uploaded person is truly a mind, they will have the same capacity for learning, reflection and personal growth. A mind modeled in software, therefore, could not help but diverge from the original (which will inevitably have different experiences) over time. Eventually, we would have not one but two distinct people. Perhaps uploading, even if it were one day possible, would not be a way to create identical copies of ourselves, but merely a very new and unusual way to reproduce.