Our niche as a species is complex tool use. I don't think it's a coincidence that tool use emerged in a species with gangly, flexible arms and opposable thumbs.

Our niche as a species is complex tool use. I don't think it's a coincidence that tool use emerged in a species with gangly, flexible arms and opposable thumbs. If cats had become hyperintelligent rather than hominids, they'd probably have difficulty whittling and weaving (as much as they love yarn!) Form follows function. We evolved intelligence partly because we needed it to make full use of our very dexterous body plan. Maybe legs aren't necessary (lots of us make do with wheelchairs okay, after all), but having two arms with many degrees of freedom, opposable thumbs and articulated digits opens a lot of doors.