How are humans able to do so much work with their forelimbs in comparison with other animals?
Answers
Humans can do so much with their forelimbs because that’s what evolution’s been selecting for the last six million years.
Most animals in existence today use (at least primarily) their mouths and noses as their main manipulative organs, meaning they use them to gran objects, pull on things, push stuff, etc.
Early primates went another route. Since evolution chose they had to be able to swing between branches with their hands without relying on claws that dig into the tree for grip, it made their hands really good at grabbing branches.
And if you think about it, grabbing branches is not that different from grabbing anything else: you put the object against your palm, close your fingers… and voila! You have an object in your hand. For this reason, primates have better grips than every other mammal, and use their mouths only as secondary instruments that complement their hands.