The euphoria presently surrounding the Human Genome Project should not blind us to the reality that both scientifically and socially the hard work is yet to come. As University of London Genetics Professor Steve Jones has said, the four most important letters in genetics today aren't A, C, G and T (the chemical bases that make up DNA), but H, Y, P and E.

The Project is, or will be when it is finished, a considerable achievement, which in scale – and expense – has rightly been compared to the Manhattan Project and the Apollo Missions, and which may in the long run have more far-reaching implications than either of them. So far, however, all it represents is an enormous, mostly undeciphered list of chemicals; making sense of which has been compared to a non-English-speaker trying to read the entire works of Shakespeare printed with no spaces and no punctuation. It can be done, but it will take a while.

This is fortunate, because it gives us a little time to consider the social ramifications. The Manhattan Project brought us the first real threat of immediate species suicide, the consequences of which we are still working out. Some say that the balance of terror kept the peace, others that it destroyed our liberty (or both, or neither) but everyone agrees that we stumbled into the nuclear age blindly, under the pressure of war, and without enough consideration. Putting that genie back into the bottle has proved, so far, impossible.

There is a similar concern that over-enthusiastic scientists, whether driven by a desire to help the afflicted or by less worthy goals, may try to apply the first fragments of human genetic knowledge without either understanding the full effects of their actions or adequately considering the social consequences.

Such anxieties are only exacerbated by statements like the following, made by the most famous molecular geneticist of all, James Watson: "Some people are going to have to have some guts and try germline therapy without completely knowing that it's going to work." 'Germline' therapy is the genetic manipulation of embryos, which will affect not only the resulting child (and adult) but all future generations as well. If it doesn't work, the result is, at best, a family tragedy; at worst, a disaster for humanity. Watson's statement comes from a recent book called Engineering the Human Germline, based on a conference held at UCLA, which features many of the most prominent scientists in the field, almost all of whom are in favor of it.

Professor Lee Silver, of Princeton, has written a popular-science book called Remaking Eden, in which he not merely envisages but describes as inevitable a society in which the ruling class becomes genetically distinct from the majority of people; becomes, in fact, a different species. Such an atavistic reversion to aristocracy is, of course, by no means unavoidable, and the pseudo-scientific speculation that leads to it may be no more realistic than time travel, but this kind of proposal for the use of the new human genetic technologies is truly horrifying. The fact that reputable scientists, the very people spending billions in government and private funds to do the basic research, even think in these terms about how their work might be applied should be cause for alarm among the general public.

Over the coming several years we will need to engage in a broad process of education and discussion concerning the new human genetic technologies. Much broader, indeed, than the academic discipline of bioethics. To their credit, universities have helped to promote this novel discipline to confront the novel issues this technology raises, but all too often its participants are funded and even supervised by the very scientists they are supposed to advise. At the University of Pennsylvania, the Center for Bioethics was, until recently, part of the Institute for Human Gene Therapy, and one component of the Jesse Gelsinger tragedy (he died there after an experimental use of gene therapy) was that there was no external ethical review of the procedure, merely informal conversations between Arthur Caplan, the bioethics center director, and his boss, James Wilson, who decided on the procedure.

Similarly, Lori Andrews, a law professor with long experience in reproductive issues, has written scathingly of the reasons for her resignation from the Working Group set up to consider the Ethical, Legal, and Social Implications of the Human Genome Project (ELSI). By her account, it was deliberately created "not to set ethical standards but to let the science proceed unimpeded."

The science is important, and may lead to better medicine and possibly even greater understanding of who we are. But it is shockingly hubristic to suggest that anyone knows what we can do, what we shall be able to do, and especially what we ought to do. As yet, we barely know how to discuss the issues. We urgently need to summon up the maturity and commitment required to distinguish between those potential applications that are beneficial and deserve our support, and those that could open the door to a terrible future of human techno-eugenic manipulation, and should not be allowed.

This is a social and political process, but there is nothing new about that. As a global society, we have decided, for example, that chemical warfare should be outlawed and that prisoners of war should be treated with a certain minimum respect. There has been progress towards the elimination of nuclear testing, and even though nuclear proliferation continues there is widespread acceptance that we should – together – restrict the deployment of these weapons. That something is technically feasible does not mean it is socially acceptable.

The Council of Europe is already in the process of enacting a ban on modifying the genes we pass on to our children. Canada, Australia and Japan are also considering such laws. The United States needs to join this dialog, bring in all the other nations of the world, and help to create a global agreement on how to regulate these technologies.

This may sound like a tall order, and indeed the prospect of building a world-wide consensus is daunting. But the effort is essential when you consider what is at stake: the continued existence of the human species as we know it.