The worlds of Baron  baroncoon Engel’s imagination are populated by, among sundry others, a myriad of species that would be recognizable to a human of our world as resembling anthropomorphized versions of many of the extant modern mammals. One of the less immediately obvious, but nonetheless most striking, similarities to humans in the real world is the presence of scalp hair on many of these furry individuals.

Structurally, this hair is similar to real-world human head hair: long, robust, interspersed with sweat glands, and lacking the awn hairs of fur. The full range of real-world-human colors—with the addition of white—and consistencies appears, though some people have stripes of differing colors in their hair and tight curls seem to be less common. Baldness, including male-pattern baldness, does occur, but is rarer than in the real world. Body fur does not, unfortunately for the victims, follow retreating hairlines to fill in bald areas.

Genetically, the scalp appears to be divided into two regions. The crown extends from the forehead over the top of the head to a line extending from ear to ear and passing over the point at which the hair changes direction. The mane extends from that line down the back of the head to the nape. Hair may grow on both regions, on only one or the other region, or on neither region. Where it does not grow, body fur takes its place. In babies (or pups or kits or what-have-you), the typical real-world human pattern of baby down followed by “adult” hair occurs.

Clearly, some sort of genetic “on-off switch” for each region must exist in these species. These switches must be separate from the determinants for color and consistency, because the hair on individuals with full heads tends to be the same on both regions. They must not be sex-linked, because there seems to be no significant difference between the sexes in the population at large. Different species seem to have some limited variation: equines, for instance, tend almost exclusively to be full-headed or have mane-only hair, and male lions almost invariably are full-headed. However, in the population as a whole, there seems to be a general pattern of distribution.

It is this pattern of distribution that is more mysterious and requires an explanation (and is, no doubt, the subject of countless university-student theses in those worlds). Most common is the full head, with scalp hair growing on both regions. Next most common is crown-only hair, with fur growing on the mane region. Third is no scalp hair, with fur growing on both regions. Least common is mane-only hair, with fur growing on the crown region.

Using a reasonably comprehensive poll of existing significant characters—that is, characters who have had the equivalent of “speaking roles”—yields some interesting numbers. (Since this was originally written, the number of characters has grown significantly; such new characters were not included.) These numbers are presented in the table below. “On” means scalp hair is present; “off” means no scalp hair is present, and fur takes its place.

[pre]     –––––––Crown–––––––
Mane –––on–––– –––off––– total
on 56 (48.7%) 2 (1.7%) 58 (50.4%)
off 33 (28.7%) 24 (20.9%) 57 (49.6%)
total 89 (77.4%) 26 (22.6%) 115 individuals[/pre]

Obviously this is a very small sample when attempting to determine trends for large populations, but still it is suggestive. Crown hair appears to follow approximately the classic 3:1 proportions for a single dominant-recessive gene, but mane hair appears to occur in roughly 1:1 proportions. The interaction of the two, though, is even stranger, as shown in the table below. Of particular interest is the fact that mane-only hair is less common, by a wide margin, than no scalp hair at all.

[pre]Crown Mane Proportions
on on 1 in 2
on off 1 in 3.5
off on 1 in 57.5
off off 1 in 5[/pre]

The fundamental question is: what genetic mechanism would account for this distribution?