African Erectus co-evolved into large brains and wide female pelvises for brithgiving

New skeletal finds at Gona, in northern Ethiopia, show that H. erectus females had already very wide hips, needed to deliver big brained childs. The find is dated to some 1.4 million years ago.

From left to right: top view of the pelvises of Lucy (an Austraolpithecus), the new Gona H. erectus find and modern human.

Source: BBC: Human ancestros born big brained.