I think there is a grand misunderstanding around my use of machine learning. Your first two suggestions have an assumption that the images weren't heavily modified before going into Artbreeder which was usually the case. or modified in a circular manner, Artbreeder>Photoshop>Artbreeder>Photoshop any kind of MD5 is lost. I could show a progres of each but it is absolutely enormous. Potentially hundreds of decision trees.

As for GAN bias: once in Artbreeder the skin tone is entirely my choosing. If there is a bias in the depiction it is my own bias. There might be a slight bias towards a white, brow-haired female but is is more of a gravity that can be avoided with a bit of skill. There is also a challenge in hair that is -for lack of a better explanation- hair made with human intervention (braids, tall wigs, cornrows, dreads etc).

AS for your last suggestion: I've already been thinking of making videos that show a transition of skin ton of lightest plausible to darkest plausible. Tiberius for example I have a very compelling version as a pale-skinned white dude or a dark-skinned person who looks indian/pakistani. Done in paintover/colorization in Photoshop --directly on the bust- where proportions match.

In the second version of the poster I actually challenged myself to do at least do a quick depiction of each emperor with dark skin. Version 1 my approach was to assuming an average based on place of birth. This time I experimented with assume-darkest-features possible simply to test my assumptions and question my biases. Although quick and not robust, I think it was of value.