In this post we're returning to the theme of pigmentation. Namely the relationship between eumelanin (black/brown pigment) and pheomelanin (red/yellow). Redheads tend to have higher pheomelanin relative to eumelanin. For non-redheads the ratio of eumelanin to pheomelanin is pretty similar, regardless of skin tone. So a light-skinned person will have low levels of both pigments, but in a ratio of 3:1. Likewise a darker skinned person will have higher levels of both pigments, but also in a similar ratio of 3:1. (Note: This is an over simplification, to help explain the broad concept, in reality the numbers aren't this simple.) However, for redheads the ratio of pheomelanin is higher.
So non-redheads might have 75% eumelanin and 25% pheomelanin,
Whereas for redheads it might be more like 60% eumelanin and 40% pheomelanin.
(Again, take these numbers with a pinch of salt. If you want a deeper understanding search some scientific papers on the topic.)
We've made the argument on here before that redheads are a product of 'melting pot' cultures that give rise to the conditions needed for this relatively higher pheomelanin. For example, a person may inherit lower eumelanin from their lighter-skinned ancestors, but the higher pheomelanin from their darker-skinned forebears. So, according to this theory, populations that are diverse, that have light-skinned and dark-skinned people in the gene pool, will throw up redheads due to this lottery of genetics.
(For more on this see here: Melting Pots Part III)
Sensitive Redheads.
Anyhow, the red pigment pheomelanin is also what makes other parts of the body red, like the lips, nipples and genitals. These parts of the body also tend to be very sensitive and have a lot of nerve endings. So given this it makes sense that redheads, people with higher pheomelanin in general, would also be more sensitive in general ..and this is often what's reported. That redheads are more sensitive to pain and temperature changes. That they need more anaesthetic at the dentist, and so forth.
It may also go some way in explaining the stereotype of redheads being more sexually sensitive.
Likewise, we also have the stereotype of redheaded males being viewed as more effeminate. With hair and skin colour it's often the case that fair hair is seen as feminine and dark hair as masculine - note the stereotype of the "tall, dark handsome" male and the "ditzy, blonde" female. So perhaps redheaded males get the double whammy effect. The fairness - low eumelanin - complete with the cultural perception attached to that, coupled with the heightened sensitivity caused by the higher pheomelanin. Essentially: fair + sensitive = very feminine.
Again, as noted above, things are never quite this simple in reality, and there may be factors we're not considering. However, overall, it does feel like all this ties together quite nicely, and makes sense in regard what you would expect if you turned up the genetic dial on redness.
