Human beings can be genefixed, genetic upgrades, or parahumans. All have full human rights, but some governments restrict the gengineering that can be done. Most nations do not permit gengineering that poses physical or mental health risks, stunts or degrades normal human abilities, or encourages criminal behavior. Some places, such as the European Union and Japan, do not approve any modification that might result in a child suffering social alienation: no tails or fur, for example. A waiver is possible for pantropic changes optimized for a colonial environment.

When parents decide to have a child, they usually visit a genetic clinic and assay their own genomes. They often pay for eugenic genetic engineering to fix defects such as hereditary diseases. This is known as being 'genefixed'. Since the 2040s, genefixing has been gradually extended to apply to tendencies to 'flaws' such as lantern jaw, knock-knees, poor complexion, crooked teeth, etc. It is also possible to edit gene sequences tending toward certain mental states, such as lecherousness or poor self-control, or to reduce susceptibility to some mental illnesses. It's generally considered acceptable for parents to do this.

A genetic upgrade is a person whose genes have been carefully selected (see Eugenic Gengineering) not only to fix defects but to enhance certain traits (such as appearance, health, or memory.) If their clones and descendants are included, upgrades make up about one-fifth of humanity. This is closer to one-third in Fifth Wave countries such as France and the United States, where young people lacking upgrades are beginning to be stigmatized.

Genetic clinics offer a variety of 'overlay templates', which provide specific genetic traits while leaving most of the parental DNA alone, or which can be merged with known upgrade gene lines. Such templates do not necessarily bring about simple cosmetic changes (a child can be a member of a wholly distinct species even with 98% of its DNA left unmodified). More ambitious parents may choose not to bequeath their genes to their children at all, calling instead for a wholly customized design. This degree of intervention is expensive and is strictly regulated in some countries, but it is usually possible.

Most upgrades come from proven commercial genetic templates ('gene lines'). Selecting one is vastly cheaper than customized eugeneering, since the work has already been done and hidden defects are unlikely to appear. A more subtle advantage is that certain gene lines establish their own subcultures and support groups. Being an Alpha upgrade means you have several million relatives.

A parahuman is a transgenic person (see Species Modification) whose genome incorporates genes of nonhuman origin, giving him traits that normal humans do not possess. These can range from the strikingly obvious (a coat of fur) to the subtle (a biochemistry adapted to zero gravity).

Each type of parahuman is technically a different species from humanity. With rare exceptions, they are no longer naturally interfertile with other humans or different parahuman species. If a parahuman and a normal human wanted to produce a child, for example, they'd need to blend their DNA via gengineering.

There are several million parahumans in the system. They represent about one-tenth of one percent of Earth's population. However, over one-third of human beings beyond Earth's orbit are parahumans.

Pantropic Parahumans: These are humans whose bodies possess genetic modifications that make them better able to live in a hostile environment. Examples include adaptations for Mars or micro-gravity, and 'econiche' parahumans optimized for harsh Earth environments such as desert or ocean habitats.

Ideal Parahumans: These are humans whose genomes were modified to conform to an individual or group's idea of what the human body should be like, or a particular aesthetic vision.

Specialized Parahuman: These are humans physically or mentally optimized for a particular occupation. A small degree of specialized enhancement (for example, a body well-suited for athletic pursuits) is considered ethical, but overspecialization that takes away some of a person's free will or dignity is not.