Low-level genetic engineering is so common among humans as to hardly even be worth mentioning. Parents have picked hair, eye, and skin colours for their children for over half a millenium. Many genetic diseases have been eliminated by routine gene therapy, and today's average human is faster, stronger, and more intelligent than any twenty-first century human.
The best years of genetic engineering for humanity were in the twenty-third and twenty-fourth centuries, when new horizons were still in sight and advancement followed hard upon advancement. However, as the number of modifications made to human genomes increased, so too did complexity and risk. Infertility, new diseases, and serious later-life health problems ran rampant. By 2404, seven out of ten children receiving extensive in-vitro gene therapy were rendered sterile, and almost all suffered severely. Other forms of genetic disorder and disease due to hasty and excessive genetic modifications also considerably lowered the general public's appetite for genetic modification considerably. Legal systems of the world were clogged with lawsuits and often accompanied by widespread panic, and by the time the dust had cleared, further modification was universally recognized as unsafe.
Genetic therapy advances tend to be slow and incremental in nature. While two centuries of genetic engineering had markedly improved the human race, regulations on new techniques of gene therapy meant that further development largely came to an official standstill. For those who could pay, however, there were always black-market doctors willing to perform riskier techniques. Many of the more loosely policed Martian colonies took up black market gene therapy as a major industry.
Moreover, government experimentation for military purposes never stopped and hardly slowed. In the twenty-eighth century, military gene research is largely regulated by an agreement between major military and industrial powers to prevent the rampant creation of potential "supersoldiers" and their release into the population. In particular, a fail-safe is inserted into all genetically modified soldiers to prevent fertilization between two genetic augments and to render the enhanced traits dormant to descendants. Lost over the centuries is what many genetically modified soldiers call the "omega vector," which is the key in unlocking the fail-safe, from which all "super soldier" lines descend from. All records of the omega vector had been wiped clean after the gentleman's agreement was set in place centuries ago, although it is rumoured that some corporations are secretly inserting the omega vector into their soldier lines or even more potentially explosive, that the suppressed genetic fail-safe is naturally disappearing.
Unofficially, it is widely rumoured that governments and contractors would be only too happy to gain an illegal if effective leg up on the competition with the creation of a genetically stable line of supersoldiers with long-term viability. These accusations are always flatly denied by any government official approached with them. Major military powers that engage in these practices are vigilant about any attempts to combine or otherwise perpetuate super soldier lines, considering the transfer of genetically engineered traits to be a sort of abomination. In more practical terms, the ability of supersoldiers to reproduce amongst themselves would give that particular nation an exponential advantage in the genetic augmentation 'Cold War' that has emerged.
Major corporations involved in genetic therapy as military government contractors include the European Union's Yoonjin-Rhodes Corporation and Levant-Intersomme Corporation (through their subsidiary Genospec), the Russian RESSAN Group, Korea's AhnSoft Genotech, Occupied Japan's Nakomi Concern, and Canada's Red Corporation. As well, the Republic of China's government maintains significant in-house genetic engineering assets. All these corporations and others also engage in low-level therapeutic genetic engineering.