Thanks for sharing. Note that that example is from the same research group, and also had its contrast artificially enhanced.

I find it a bit odd that the humans are so small and lack details, whereas the boar even has fur, two distinguishable toes, and seems to bend its legs correctly.

Then again, I have yet to publish something in Nature, so I'm probably a bit too skeptical for this game :)

You're not wrong to be skeptical. These papers are written for other archaeologists who have a lot more perspective on both the uncertainty inherent in the field and the games academics play thanks to publish or perish. They don't need the caveats repeated every paper like the rest of us.

The people might have been added later by a less skilled artist or even just a child doodling, they could have been drawn with more detail in another other material that didn't survive but sketched with the longer lasting stuff underneath, or they could be artifacts of the process they use to increase contrast, etc. There's a bunch of possibilities but authors will usually gravitate towards the interesting conclusion.

That said, animals drawn with higher detail than people is almost a trope in archaeology. They probably held a spiritual significance and the hunters would have spent a lot of time studying them.