*blowing out my little bedside tealight, putting away my phone, and drifting off to sleep with one last dozzy thought of gratitude to blue light screen filters, only to jolt awake because wait shit did humans evolve that way because of candles???
pre-electric light sources (candles, oil lamps, fire) tend to warm/yellow tones—and have been used in one form or another for all of human existence. use of fire pre-dates humans; our hominid ancestors were using it for light and heat as early as 2 million years ago.
for a long, long time, yellow light (the open fire, the communal hearth, the candlelight, the burning lamp) has been an indicator that hey sweetheart, it’s almost bedtime
and as for blue light, well. they called that daylight (and sometimes: dawn)