Peter Rodman proposed that human evolution was linked to while Owen Lovejoy suggested the best explanation was

the increased efficiency in walking as forests transformed to wooded environments; the ability to carry food in order to provision family members

the ability to carry food in order to provision family members; increased efficiency in walking as forests transformed to wooded environments

the ability to make and use stone tools; the loss of the diastema and evolution of thick enamel

the early emergence of a large brain; the later emergence of a large brain