Origins of the pale skin color in Europeans

[Anomalocaris]

And what? They all hang out in the clearings to work on their tans?

As a matter of fact, the villages where they live and spend much of their time socializing would most likely be located in a clearing. They may not deliberately be trying to catch any rays but they will under such conditions.

Perhaps that has as much to do with darkness under the canopy being demonstratably psychologically depressing, then with any desire to bake under the sun in particular.