My (limited!) understanding is that dark skin is a protective adaptation to prolonged strong sunlight, so it would make sense that it would be more reflective (so shinier) than lighter skin. The pigmentation is in the top layer of skin, the edipermis; the deeper layers are exactly the same. The reddishness in skin comes from the blood vessels in the deeper layers - one of the possible issues could be that the measurements used in Poser's SSS implementation are derived from lighter skin tones.

A specular map would definitely be needed - from what I remember, areas where bone is close to the surface of the skin tend to be more reflective, as are areas that are naturally moist or oily.

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