What traits are only found in human-like primates and why do you think they may have been selected for in human evolution?

Chins. We have NO IDEA why ONLY humans have chins. Not even Neanderthals had chins.

Primates are well known for using tools for hunting or gathering food and water, cover for rain, and self-defence.

Humans: **** sapiens

only

Human-like primates: every single human-ancestor. Is that hard to understand?

Once the species has changed enough at genetic level, they are no longer the same thing although they still can look similar.

A wide variety of environmental factors are always at work so finding that magic bullet probably isn't going to happen and the human branches with cross over genetics also has a learned behavior trait that follows

everything from making fire to wearing clothes and remember before we became the dominant species we were the prey which his part of that environmental factor.... 

None. Humans are animals.

You'll have to be a bit more specific.

What do you mean by "human-like" primates?

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re: your update - The reason I asked is because of what I suspected.  The term you used has no scientific definition.  The closest terms don't match what you're asking about.

In science, the closest thing to "human-like" is the term "anthropoid."  Generally speaking, it refers to all tailless apes.  Most species in that category are not human ancestors. 

The term "all human ancestors" includes all kinds of species that aren't even primates, much less resemble modern humans.  Even most human ancestors that were primates don't resemble us any more than any other non-ape primates today.  And you seem to be specifically excluding other modern Great Apes.

Given what your definition seems to refer to (all previous species of the genus H o m o) there really aren't any genetic traits they possessed that no other species did.  

The only trait modern humans possess that no other land animals do is the capacity for symbolic language.  Cetaceans appear to have the capacity, as may some other species.  And several human ancestors (but not all) also possessed it.

While intelligence appears to be a genetic trait, language is not.  It's more of a cultural development.

In other words, it's not something that can be "selected for" in the way you suggest.