An Evolutionary Story:
A very long time ago, perhaps more than a thousand years, there lived near the polar circle, in what is now Norway, a group of mostly redheaded Vikings, craftsmen of the long ships. At a time when they had just completed a masterful example of their craft, there blew in from the Northpole a piercingly cold wind. It brought heavy snows and made life almost unbearable. The prospect of spending another winter in this Northern habitat became just too much to contemplate. These Vikings, therefore, packed their belongings onto their new ship and steered the ship in a Southerly direction where they had hoped to find less challenging conditions. The stormy weather pushed them past the British Islands, through the Bay of Biscayne, past the Iberian peninsula and around the bulge of Africa.
They made landfall on the Westcoast of Africa near the equator, where they found the tropical vegetation to be lush with many large trees that could be used for the construction of their new homes. They soon discovered that there are also large flocks of antelope to hunt and a plentiful supply of clear water from a nearby river. Very pleased with themselves the Vikings lazed around in the hot tropical sun, but lacking the pigmentation of the pigmies and other African peoples that lived in tropical Africa they were soon full of sunblisters and had to think of ways to protect themselves against the African sun which was much more intense than the sun they had experienced in their previous habitat above the polar circle.
Centuries later a fleet of Norwegian ships navigated down the Westcoast of Africa and were surprised to find there a community of Norwegian speaking people, although in an ancient dialect perhaps more related to Icelandic. Amongst these African Norwegians, however, there were no longer any redheads and they were also more darkskinned than their Viking ancestors. They told tales of a sickness that befell their redheaded, lighter skinned compatriots during the preceding centuries. All this was recorded in the annals of ships belonging to the visiting fleet and after yet another long time the information became available to Dr Wallace Darwin in England.
Now, Dr Wallace Darwin was an expert on the biochemistry and genetics of skin pigmentation and was interested in the fate suffered by many of the ‘African’ Vikings, in no small measure because redheaded, fairskinned people are prone to develop melanoma of the skin (skin cancer). He knew that human skin and hair colour is largely determined by the amount and type of melanin pigment production by cutaneous and follicular melanocytes, which in turn depends on the relative amounts of four different proteins expressed in these cells. A key regulator of pigmentation in human melanocytes is the melanocortin-1-receptor, a protein found in the membranes of melanocytes. There are over 70 variants of this protein and depending on which variant is expressed and found on the melanocyte cell membranes, hair or skin colour can have a darker or lighter hue. The red hair colour (RHC) phenotype is associated with red hair, a fair skin and an increased risk of skin cancer. Skin cancer cells can metastasize, i.e. spread to other organs and tissues in the body with fatal consequences. The disease is about 20 times more prevalent in white males as compared to black males.
While Dr Wallace Darwin could no longer study the biochemistry of the now extinct RHC phenotype Vikings that so injudiciously made Africa their home, he was convinced that their demise is just another example of natural selection and survival of the fittest. In his opinion all this had absolutely nothing to do with thermodynamics and its second law.