Nature's light sources are the sun (full spectrum) and fire (primarily infrared).

“and that's what I want to emphasize here is nature there's only two sources of light in nature it's the Sun and it's fire and that's what we have evolved with and during the day you get full spectrum sunlight which includes everything from UV to infrared and you never get the higher energy shorter wavelengths without the infrared and then at night time we evolved with fire and it was typically low angle on the ground and the fire looks like this it looks like a 10:1 ratio of infrared divisible no ultraviolet barely any green and blue and a ton of infrared”