The variant Val92Met arose somewhere between 250,000 and 100,000 years ago, long enough for this gene to be carried by humans into central Asia. Arg160Trp is estimated to have arisen around 80,000 years ago while Arg151Cys and Asp294His have been estimated to arise around 30,000 years ago. The wide variation of the MC1R gene exists in people of European descent because of the lack of strong environmental pressures on the gene. The original allele of MC1R is coded for dark skin with a high melanin content in the cells. The high melanin content is protective in areas of high UV light exposure. The need was less as humans moved into higher latitudes where incoming sunlight has lower UV light content. The adaptation of lighter skin is needed so that individuals in higher latitudes can still absorb enough UV for the production of vitamin D.  Freckled individuals tend to tan less and have very light skin, an adaptation to allow individuals that expressed these genes to synthesise sufficient vitamin D.

Types
Ephelides describes a freckle that is flat and light brown or red and fades with a reduction of sun exposure. Ephelides are more common in those with light complexions, although they are found on people with a variety of skin tones. The regular use of sunblock can inhibit their development. Liver spots (also known as sunspots and lentigines) look like large freckles, but they form after years of exposure to the sun. Liver spots are more common in older people.
See also
Beauty mark
List of Mendelian traits in humans
Melanocortin 1 receptor
Mole

References
External links

MedicineNet.com: Freckles
Ephelides (Freckles) at eMedicine