This doesn't seem as mysterious to me as the article suggests. We were still primarily roaming hunters 1.4m years ago. It's not difficult to imagine the uses a more aerodynamic rock would have...namely, you could be more accurate throwing it.
But I'm sure this occurred to researchers, so maybe they're expressing this as "there is no evidence of how they were used" and not "we don't have some good ideas."
This doesn't seem as mysterious to me as the article suggests. We were still primarily roaming hunters 1.4m years ago. It's not difficult to imagine the uses a more aerodynamic rock would have...namely, you could be more accurate throwing it.
But I'm sure this occurred to researchers, so maybe they're expressing this as "there is no evidence of how they were used" and not "we don't have some good ideas."