Ape men

I was learning Midrash Rabba today. The midrash says (B"R 23:6) that after the generation of Enosh started worshiping avoda zara, 4 things changed in the nature of the world. One of those things is that the facial features of men became ape-like. The mefarshim on the midrash explain that this means that they lost their tzelem-elokim, they lost their human quality. Apes are described by the mefarshim as being an intermediate level between cattle and man.

I guess chazal did not really have a problem with us coming from monkeys. My question is, when was the tzelem elokim restored? my guess would be that it was restored with the covenant of Noach but the topic needs some more iyun.