I'd also consider this: threat and combative displays and hunting methods among the species you're looking through. Its a different approach than looking at whether a closed appendage is used as a utility hammer, but I think its more to the point of what we're talking about. I mean, if its a carnivore, the way it goes about using its body to kill things every day seems like a better starting point, and/or using social violence examples in pack animals where they're not trying to kill each other. If you do your approach, you'd still have to use this one afterwards anyway, once you determine FIST: Yes or No?
Not if you think about how hands developed over millions of years, with the tree shrew (our ancestor rat) growing bigger and bigger, surviving more enemies, and changing his diet from cracking nuts, to fruit, and so on until millions of years later he is a monkey smashing bananas open with hands.
I think the author's approach at studying morphology etc has more merit than just seeing if its happened before. Yes, that would provide more evidence if that were seen, but don't you see that humans are quite anomalous primates? I mean, if that's your personal burden of proof, do you accept that all human traits are found elsewhere?
The OP question as I read it was: was it normal for pre/early humans to punch things and did that activity result in 21st century man's fist, today.
I personally don't buy it unless we can also find its happened before in another species in the same way. That's my personal burden of proof for the idea that the fist is for punching.
Then why don't you see more mostly hairless incredibly intelligent but physically weak bipedal primates that utilize language and culture and reality TV?
It seems natural selection should show lots of species punching, if it were so damn effective, right? I don't know.