|An adult brunling apex (left), nadir (center), and mesa (right)|
Although brunlings and humans share a number of topical physical characteristics, neither species can be described as belonging to the same overall race of hominid. It remains unknown at which point brunlings split from humans, or how brunling even became a species of alvonatal mammals to begin with. Most anthropological records indicate a deviation from primates approximately 2–2.5 million years agos, though the divergence of brunlings from their nearest ancestor T. sunthranesis is also unclear. What is known is that the ancestors of brunlings originated from Nurthra, and likely migrated across the ancient land bridge connecting Nurthra to Sunthra around 1.8 million years ago, just prior to the land bridge's disappearance around 1.5 million BP. It was from this group that brunlings would emerge and spread across the rest of the southern continent. Ultimately, the brunlings would grow rapidly, developing highly-stratified patriarchal communities, which would expand into vast civilizations covering most of Sunthra. Today, the global population of brunlings sat at X billion as of 2023.
Brunlings are extraordinarily distinct from humans in how they think, operate, and interact with others. But above all, brunlings are distinct in how they reproduce as a species, which is what truly sets them apart from their human neighbors. Much like humans, brunlings are a sexually dimorphic species, though they possess three rather than two sexes; these are apexes (frumlings), mesas (ferelings), and nadirs (neshlings). Apexes are the sole reproducing members of their population, and are physically larger and stronger than mesas or nadirs. Mesas and nadirs possess no reproductive capabilities, and are instead defined by their general roles within the population; with mesas serving as protectors and providers, and nadirs as serfs and laborers. Apexes reproduce aesexually, and are capable of siring offspring following puberty, at around age 16, and infertility, at around age 80.
Brunlings are omnivorous, and can and will consume any edible flora or fauna available to them. Like humans, brunlings mastered the use of fire for cooking and generating warmth hundreds of thousands of years ago with their ancestor T. sunthranesis. Because of the physical differences among the brunling sexes, while apexes and mesas can survive for eight weeks without food and four days without water, nadirs can only survive for six weeks and three days without food and water. Brunlings are diurnal, sleep for approximately eight hours per day. Childbirth for the species has historically been safe, as apexes do not give birth via a narrow vaginal birth canal, but an elastic navel opening. Childcare for brunling offspring who are helpless at birth is generally divided among the sexes, with apexes providing guidance, mesas serving as wet-nurses, and nadirs handling the bulk of the day-to-day childrearing needs.
Anatomy and physiology
Brunling reproduction takes place via aesexual internal fertilization, though developments in the area of assisted reproductive technology do exist. Brunlings are particularly notable for the fact that the ostensibly "male" members of the population—the apexes—are the child-bearers within the species. The average gestation cycle for brunlings is 32 weeks, with some varying by 28–30 days. Much like humans, brunling pregnancies are divided into development stages, with the embryonic stage taking approximately 4 weeks to complete. The following 8 weeks mark the fetal stage of the pregnancy. Brunlings develop faster than humans to compensate for the smaller share of childbearing individuals in the population. Thus, by 12 weeks, brunlings may induce an early delivery in necessary for the health of the father or for other medical reasons. Brunling infants are generally 5–6 kg (11–13 lbs) in weight and 48-56 cm (19-22 in) in height at birth. The larger body mass of a brunling apex compared to a human female is believed to contribute to the greater size of the infant's body during childbirth.
Compared to humans, the entire process of childbirth is remarkably safe. Complications and health risks historically associated with the birth are very low, and have been for centuries. As apexes give birth via flexible navel openings rather than the cramped and narrow birth canals in humans, childbirth for an apex is generally straightforward and painless, with a very limited labor process associated with it. The navel opening itself is blocked by a thick strap of stem cells and fat molecules known as the lorum, which is located between the navel opening and the canubula where the infant is located. Roughly one week before the child is to be born, the lorum will begin to degrade and liquify until access to the canubula becomes available. Once access to the canubula opens, the child can be retrieved, during which time they will be pulled through and coated in the remains of the lorum, the cells of which help boost the immune system of the child and shield them from a number of diseases and viruses already exposed to the father before and during pregnancy.
Childrearing among the brunlings is a process handled at different sexes during different stages of development. The task of nursing is traditionally the duty of mesas, or delegated to nadirs with developed mammary glands, while teaching has historically been the preserve of the apexes and mesas. Like humans, brunling children are helpless at birth for the first few years of their life. The brunling lifespan is divided into various stages of life, with five stages being the commonly accepted number of stages. The accepted stages are infancy, childhood, adolescence, adulthood, and old age. These stages are generally understood to have fixed periods, though generally typified by a rapid growth spurt during adolescence, and the rapid onset of senescence during the last 10-15 years of life. Apexes lose fertility around the age of 80. This process is very rapid, taking place in the last year of fertility, with the reproductive cycle of an apex shutting down permanently. It is believed this process prevents overpopulation as an apexes odds of siring apex offspring increases late in life.
The lifespan of brunling individuals varies greatly based on sex, genetics, lifestyle choices, and location of birth and upbringing. For primarily biological reasons, apexes outlive both mesas and nadirs by an average of 20 years. As of 2022, the life expectancy at birth for an apex was estimated to be 108.6 years, compared to 96.2 years for nadirs and 91.3 years for mesas. Within the less-developed regions of the brunling world, the median age is much lower due to higher mortality rates. As a species, there were approximately 480,000 centenarians (brunlings 100 years or older) worldwide in 2020.