Apologies if you know this already, but ...

That's likely exactly how these pictures were generated.

Generative adversarial neural networks (the typical approach for this type of problem) have two nets that compete against each other.

One net tries to generate images that look like the sample data, the other one tries to tell them apart.

This is how adversarial networks work. You have a network trying to build images of humans and another one trying to guess what image is from that network and what image is real.