In this website you will learn more about some studies which claims that human ancestors shuffled before walking. It says there must be common ancestors' between the split of primates and humans. It says the ancestors may have began lifting up their torsos and shuffling on two feet for short distances between nine and sixteen meters when aiming for high-hanging food.
It also says that Moving on two legs for short distances required less energy than returning to all fours to move to the next foraging spot. The link to this website is as follows.
news.nationalgeographic.com/news/2008/06/080611-ancestor-shuffle.