As is, perhaps, inevitable between species so closely related and physically alike, sexual contact is not unknown, if also not common nor encouraged. It occurs most often in the takma river towns (at least, those from which the xtauh are not banned), although sadly many such instances are not voluntary; many of those that are are essentially on the level of prostitution, trading sex for some form of payment. While entirely free and loving relationships probably exist, they are usually either hidden well or prone to being forcibly ended by outraged observers.

In all cases, liaisons are more common between a female takma and a male xtauh, partly because of a tendency toward dominating female behavior in both species but mostly because of the difficulties of size; males are also the smaller sex in both species. A smaller male, takma or xtauh, seems more natural; whereas a female xtauh engaging with a male takma, on the other hand, are more likely to find themselves uncomfortable in a reversal of sizes (though, considering the individuality of sexual preferences, this is not to be taken as an absolute rule). Although it is usually not a formal consideration, the possibility of offspring also argues in favor of the more likely pairing; a cross-species gestation for the larger takma female is likely to be much easier than for the smaller xtauh one.

That said, while sex is certainly known (however disdained), successful reproduction is less so. Takmar possess a possible scale type that is entirely missing in the xtauh, and which is a dominant genetic trait in the former species; therefore, unions involving a takma with spongiform scales will generally not result in living offspring, or else offspring that will have a lower life expectancy due to scale afflictions. Takmar with massive or stratified scales, by contrast, are more likely to successfully produce living hybrid children, albeit at a discouraging rate - no more than 75% hatch from the egg, and often another half of those are either not themselves fertile or die from various health conditions before puberty. The ones who are both healthy and fertile frequently have impaired or absent hearing, due to differences in antenna structure between the species.

The earliest takmins diverged from the dvidalins approximately 74,000 cycles before the present. These pre-takmar, common ancestors of both the takmar and the xtauh, originally possessed - as did the dvidalins - two main scale types, massive and cavitated. The internal structure of the former involved scales forming as solid masses, while that of the latter had scales that were scattered throughout by microscopic cavities or bubbles. The evolutionary significance of cavitated scales is unclear, but after enjoying an initial period of continuing success as a significant minority scale type, it began to dwindle away in favor of the massive type - possibly related to their ability to help retain water - and nearly disappeared after the appearance of stratified scales as a development from the massive type approximately 52,000 cycles ago.

Pre-takmar had by thirty-five thousand cycles ago evolved a strategy of cooperative polyandry as a strategy for rearing their young in the resource-scarce environment of the desert now called the Brightness. A female of breeding age, assuming she could find and attract unattached males, would attempt to acquire more than one to cohabit and mate with, with all males collaboratively caring for their young. The female would then become the alpha of a pack consisting of herself, her mates, their immature and adolescent offspring, and possibly adult daughters. Males left the pack during adolescence to seek their own mates. Females would stay on longer, to aid in hunting and possibly caring for their younger siblings, but would eventually either likewise depart, or be evicted by their mother, when searching for mates; or, in the case of the youngest daughter, shoulder aside her elderly mother to assume leadership of the pack and its territory.

Over time, packs began interacting more strongly with each other, spurring the development of linguistic ability, tool use, and, particularly in the prime territory nearest to water sources, more complicated pack structures. Nonetheless, the pre-takmar remained relatively uniform until the climate shift of between eighteen and nine thousand cycles ago, which resulted in the decrease of rainfall over the Brightness, the slow degradation of vegetation, and the disappearance of smaller lakes and streams. With food and water increasingly scarce, competition between packs became more intense, and drove a genetic divergence between the populations clustered nearest the remaining rivers (proto-takmar) and those on the fringes of the wastes (proto-xtauh); among the differences was the tendency of the former to retain the more complicated social structures and higher population densities they had gained, while the latter reverted to smaller, more easily maintained packs. At the same time, the proto-takmar became prone to develop the spongiform scale type, possibly a development of latent cavitated scales genes retained from their pre-takmar ancestors.

Nonetheless, as their habitat continued to shrink, the proto-takmar found their opportunities in the Brightness increasingly restricted. Many packs and tribes began to migrate south over the Spine of Sirdanth into the Cerulean Tangle beginning around fifteen thousand cycles ago, splitting the proto-takmar further into a northern and southern population. The northern proto-takmar continued to dwindle, with more migrating south to assimilate with their southern cousins, and the remainder dying out and interbreeding with the proto-xtauh, until no more could be said to remain by about six thousand cycles ago. With the northern proto-takmar now no longer providing a genetic bridge between them, the division into xtauh and takmar could be said to be complete. In the humid, green environments of the Tangle, the spongiform scale type proved to be far more advantageous than than the massive type that had previously predominated, and - particularly in the lowlands - came to be the dominant scale type by 3,800 cycles ago.