I enjoy watching the various "Planet Earth" series narrated by David Attenborough on the BBC America channel; I've seen bits of some of the episodes multiple times. A vital aspect of life on Earth, especially animal life, is, of course, producing the next generation. Mating and the care of offspring occupy a lot of footage on those programs. A constant viewer soon notices that most animals other than primates have fixed breeding seasons at particular set times. Once a year, for however long the process takes, all members of a given species enter the mating period. They all focus their total attention and energy on finding partners and producing offspring. For the rest of the year, they return to whatever constitutes "normal life" for their species, perhaps now with young to care for. It's striking to watch films of thousands of penguins or seals, for instance, crowding onto beaches for their annual mating rites. Some of them, such as penguins, practice lifelong monogamy, yet they engage in sexual activity only during that brief period.
Suppose a sapient species had a similar pattern, everybody in their society becoming fertile at once, all of them compelled to mate within a period of a few weeks or miss their chances to become parents? Wouldn't the entire society essentially shut down for that period, sort of like an extended Mardi Gras but with no sober police force or other authorities to keep the madness under control? The hermaphroditic humanoids in Ursula Le Guin's LEFT HAND OF DARKNESS go into "heat" for a few days every month, but they don't all enter that condition at the same time. How would an entire alien culture subject to an annual, universal breeding season handle it? Maybe people become infertile after a certain age, and the elders in their society have the responsibility to keep civilization running smoothly until citizens of reproductive age get back to normal. Would civilization as we know it have taken longer to evolve on that planet, with the yearly mating frenzy as a distraction?
In the opposite situation, some species have only one breeder or breeding couple in a group (e. g., bees, naked mole rats, wolves). An alien society with that reproductive pattern would presumably display none of the preoccupation with sexuality that drives so much of human law, custom, and emotional life.
Wildlife documentaries offer a wealth of information about exotic (to us) biological traits that could inspire alien species.
Margaret L. CarterCarter's Crypt