One of the interesting elements of space fantasy campaigns is that they let GMs experiment with really different species—as opposed to races—and the civilizations and cultures that they might develop. With that in mind, presented here are suggestions for the ways in which creatures' biology can contribute to how they interact socially, politically and religiously, thus creating interesting backdrops for interplanetary adventures.
The Default: Various Types of Mammals
Humans are almost guaranteed, of course, with elves and dwarves a close second, probably some kind of halfling, and maybe gnomes and half-orcs. Whatever the case, the dominant races in most campaign worlds are various types of mammals. (Thus the same can be said, too, for many of the NPC races in settings, such as orcs and other humanoids, giants and the like.) They give life birth, and even larger litters—that is to say, multiple births—are relatively small in number. Offspring usually know who their mothers are, and thus most likely their fathers, too. Additionally, children remain at home for a lengthy period of time before they can provide for themselves.
These factors taken together mean that family connections become quite important, and thus can lead to predominantly matriarchal or patriarchal systems of government, laws of inheritance, and such (such as among the Amazons or more traditionally medieval societies). As a result, characters who don't have families—orphans, foundlings, loners and the like—might find it more difficult to work their way into certain social circles, but areas that see lots of travelers won't present much of a problem.
Something a Little Different: Reptiloids
In many ways, the cultures and civilizations built by reptiloid species are similar to mammalian ones. Take, for instance, the lizard folk and troglodytes, both presented in the Bestiary, or the serpentfolk presented in Bestiary 2 along with supplements from Green Ronin's Freeport setting. For them, the concept of family can still be quite important. Because young are hatched from eggs, however, there is less certainty regarding parentage, and thus the society might take more of a communal outlook toward caring for them. Since more young are born at one time, less value is placed on each individual. What is more, since hatchlings are sometimes even expected to fend for themselves right from the start, this means that close family ties are less developed. While there can be individuals who seek to promote the well-being of the whole species, others are just as likely (if not more so) to be concerned only with their own survival and success. Taken further, this can lead to a culture in which greater strength—perhaps demonstrated through prowess in combat—becomes the means of attaining positions of leadership, rather than promotion through communal decision-making.
All of One (Hive) Mind: Insectoids
Along with lots of other creatures, Bestiary 4 presents the formians. These sentient insects have a society dominated by a central figure, the queen. From an individual perspective, all that matters is following her orders; she, then, provides the materials needed for life to her loyal followers. There is virtually no sense of self-determination; indeed, those who think to follow their own paths are deemed to be deviants at best and at worst, threats to peace and stability. Because large numbers of creatures are born from clutches of eggs, they are not seen as being of individual importance. Instead, all that matters is what they can do to serve the queen. They work together to generate foodstuffs and accumulate other goods, all of which remain under the queen's control, for her to distribute as she deems appropriate. In theory she should have no favorites among her loyal followers, but in practice that is not always the case.
Unhindered by Bonds of Blood: Arborlings
An eponymously titled PDF supplement from Clockwork Gnome Publishing presents an interesting variant species, the intelligent and mobile tree creatures known as arborlings. As sentient plants, they are born through the spreading of seeds or pollen; this is a relatively anonymous process when compared to live birth or even hatching from eggs. For this reason, while a given creature might feel some sense of kinship for its offspring, a much greater emphasis is put on individuality. That is, one cannot be expected to heed a parent's wishes when it is almost impossible to prove parentage. What is more, since the earth, water and sunlight provide the materials necessary for survival, and those are commonly available to all creatures, then there is little cause for competition in acquiring them. This tend to makes for a peaceful society, and one in which decisions are made through discussion of the common good rather than any sense of obedience to any authority.
An exception, can arise, however, when outsiders threaten the territory in which these creatures live. At such times, when they are forced to band together in mutual self-defense, then a charismatic and crafty leader might arise to rally them in battle.
Beyond the Pale: The Undead
Taking the strangeness even a step further, one can consider a society made up of the undead. They don't need to reproduce through any natural means; rather they can be created in a number of ways. Some, like skeletons and zombies, are simply the animated remains of living creatures; they lack any real drive of their own, but simply follow orders. Others, such as ghosts, wraiths and spectres, come into being when a mortal dies and—for one reason or another—is unable to attain any peaceful kind of afterlife. Finally there are those who enter into undeath knowingly: the lich, a wizard who seeks a kind of immortality; and the vampire, who willingly or unwillingly participate in the blood ritual.
An interesting aspect of life (for lack of a better term) in a predominantly undead society is the strict hierarchy that exists among these types of creatures. As mentioned above, skeletons and zombies are clearly of the lowest stature. Above them are some of those like ghouls, ghasts, wights and wraiths, who possess greater power but who cannot to rise above their given positions. It is only among the ghosts, vampires and liches that can aspire to any real power. In this way they tend to build up their own centers of influence, commanding those beneath them while working toward their individual ends. While they may work together toward common purposes, they are just as likely to betray each other, since there is no love lost among their kind. Their main weakness is a reliance on living creatures for food, be that in the form of blood, brains or flesh. They do have the benefit of time, however, since they can plot action over the course of decades, centuries and even millenia.
Lifespan and Outlook on Life
When considering the outlooks of different cultures and societies, it is important to keep in mind how long each of them lives. Humans, for example, are considered by others to be impetuous and grasping, in part because they typically live for less than a century. While halflings and half-orcs are pretty similar in nature, dwarves, gnomes and elves tend to view them as short-sighted. In this way, the formians are much more like humans in nature, while arborlings and lizard folk tend to see things in the same way as the older races. Only among the undead does time truly lose its relevance.