A month ago, I published that the length of the internal circadian day varies among races; African-Americans have a shorter internal circadian day relative to Caucasians, evoking public health concerns about both productive and error-prone work times, and adjustment to shift-work. The same research group, very near and dear to the Carskadon lab, has just observed that phase-resetting of the circadian day, comparable to that experienced during travel across time zones, is independent of eye color.
Why was eye color a salient concern worthy of scientific merit in the first place? It has been shown that melatonin release triggered by the pineal gland’s sensitivity to dim-light and/or darkness is mediated by eye color.
The two eye colors of interest were brown and blue eyes, but what about green and hazel? For those with hazel eyes, myself included, the eye color changes with lighting intensities, or at least mine do; in bright sunlight and ambient light, my eyes are aquamarine, and in dimmer light, are forest green.
Hmmmm, I wonder what about my mice’s (pronounced meces) beady eyes…..