The biology of the goblinoids is strange and unfamiliar to scholars of other races. Much of their body chemistry, including their digestive and immune systems, is formed of various parasitic organisms, some fungal and some bacterial. This is perhaps why Blackroot is so effective as a poison against them, it is an agent that attacks some of their core parasitic systems. If such parasites are partially self replicating and self healing, this goes someway to explaining the goblinoid ability to shrug off many injuries that would kill or incapacitate a man and eventually heal themselves to full health.
Another strange aspect of their biochemistry is their propensity for rapid evolving. Within the time of just one or two generations they have demonstrated themselves to be able to adapt to the prevailing circumstances in they find themselves in order to better survive. The ability of goblinoids to rapidly adapt leads to blurring of the traditional goblinoid species lines as drawn by other races, though most individuals are recognisable as belonging to one or other of the species. Some rare groups of goblinoids adapt to such exceptional conditions that their adaption can appear almost Chaotic. Some sample adaptions include those covered by Kevin Coleman in his article in White Dwarf 268. This is rapid species change in human terms, though not so rapid as to be considered spontaneous mutation in the Chaotic sense. The ability helps strengthen the Sigmarite case that the greenskins are in fact allied to Chaos, however.
There is widespread confusion in human circles regarding the greenskin method of reproduction, and indeed whether greenskin females exist. The truth is that they do exist, but for reasons that have yet to be adequately explained are less common than their male counterparts. Being relatively rare, females are generally kept for himself by the Warboss and his highest ranking underlings. Greenskin females are generally similar size and build to their male counterparts and thus do not stand out in a greenskin tribe or horde when large numbers of greenskins are encountered by humans.
There have been reports of pregnant human women, raped on goblinoid raids, giving birth to deformed individuals, seemingly mutants. While in the Old World one can never be sure, some of these are the result of goblinoid parasitic agents invading the developing baby and warping their body. The resulting mutant offspring, therefore, could be considered to be half goblinoid in biology and appearance. This propensity to induce mutant births is just one more reason for the Sigmarites and putitans to hate the goblinoids.
Goblinoid females vary in their gestation period from four months (Snotlings), six months (Goblins and Lesser Goblins) to approximately eight months (Orcs, Savage Orcs, Hobgoblins and Black Orcs), the period being very much linked to the average height of the species. The period is shorter than normally the case for an equivalent sized human, and generally the smaller the species, the bigger the brood - goblinoids breed quickly. Snotlings can have broods of ten or more at a time.
More on goblinoid females and reproductive behaviour is available in the Culture chapter.
Right from birth, goblinoids grow physically quickly. Orcs and the bigger goblinoids soon develop a strong, thick-boned, skeleton and their muscles rapidly put on mass and harden. Goblinoid physical size is also a function of status (or perceived status). Individuals in the tribe often develop muscle mass as they progress up the ranks, or prepare to make a challenge to move up the ranks. Thus an Orc Boss or Warboss can sometimes tell a challenge is in the offing if an underling is putting on mass in this way.
In contrast, goblinoids mental development is not as fast. Intellectual and emotional development comes with age, but not quickly. Imagine a race most of whose individuals are the emotional equivalent of adolescent teenagers, and you have a good measure of the goblinoid emotional psyche. The most balanced and stable members of a tribe are often the eldest. Shamans have the particular distinction of perhaps understanding most about the world in which they live, while at the same time being the most obviously zany due to the large amounts of hallucinogenic mushroom they are wont to consume.
Goblinoid youngsters are kept under watch by some of the older members of the tribe until they come of age when they are set loose to find their own way in the tribe. This is not only for reasons of natural goblinoid boisterousness, but also to watch for signs for shamanistic calling that often occur at this time in those affected.