There’s quite a bit of evidence they knew what other people looked like. Western Christianity goes big in Italy and they have regular trade contact with the Levant and Northern Africa.
That trade contact comes to the entirety of Europe thanks to the Byzantine Empire, also known as the Eastern Roman Empire.
Or because at that time they only knew white people so they assumed he looks like a person.
It doesn’t even have to be some subconscious ethnocentrism. It could just be someone painting what they know people to look like.
There’s quite a bit of evidence they knew what other people looked like. Western Christianity goes big in Italy and they have regular trade contact with the Levant and Northern Africa.
That trade contact comes to the entirety of Europe thanks to the Byzantine Empire, also known as the Eastern Roman Empire.