3 ms·
Sunlight. We can synthesize vitamin D ourselves when exposed to sunlight. One of the explanations I've seen for why Europeans are white is to enhance this effe
by lambda 12y ago
Sunlight. We can synthesize vitamin D ourselves when exposed to sunlight.
One of the explanations I've seen for why Europeans are white is to enhance this effect, because Europe gets comparatively less sunlight than other regions in which civilization initially spread, but was warm enough due to the gulf stream to support agriculture, which produces a diet lower in vitamin D. So between the comparatively lower sunlight and agriculture, Europeans needed to evolve to be able to generate more vitamin D from sunlight, which losing pigmentation helps with.
- SilasX 12y agoHow does losing pigmentation help? Darker skin would absorb more sunlight.
- jjoonathan 12y agoAbsorbing photons into melanin pigment and dispersing their energy as vibrational motion (heat) doesn't help synthesize vitamin D. For the synthesis you need the photons to hit an intermediate molecule in the pathway and boost an electron into an excited state. If there's a bunch of melanin absorbing photons before they get to the synthesis pathway, the synthesis will be inhibited.
- carey 12y agoLess sunlight being absorbed by eumelanin in the skin means more sunlight left to be converted to vitamin D. Window glass also blocks most of the UVB part of the sunlight that would be converted to vitamin D.