Final answer:
The earliest hominins looked very ape-like due to their close evolutionary relationship with apes, retaining many physical features suited for arboreal life. As evolution progressed, species like Homo habilis and Homo erectus developed traits hinting at a transition to more human-like features while still possessing ape-like characteristics.
Step-by-step explanation:
The earliest hominins, or human ancestors, such as Australopithecus, looked very ape-like primarily due to their evolutionary heritage. Australopithecus, which evolved about 3.9 million years ago, shares a common ancestor with apes, and though it exhibited some key human-like traits such as bipedalism, it also retained many ape-like features. These include long arms, which are suitable for brachiation (moving through trees using the arms), and other morphological characteristics like a small brain relative to body mass, larger teeth, and a prominent jaw. The skeletal structure of Australopithecus shows a mixed adaptation for both arboreal activity and bipedal locomotion.
A transition species like Homo habilis still possessed many ape-like qualities such as long arms and small stature but also had a larger brain and smaller teeth, characteristic of later human ancestors. Homo erectus progressed further, developing physical traits that made bipedalism more efficient, such as a broader pelvis and longer legs. However, they still exhibited a sloping forehead and larger jaws indicative of their ancient lineage.
Overall, the evolution of hominins from ape-like ancestors was a gradual process, reflecting each species' adaptation to its environment. Fossil records, such as those of Ardipithecus, show a progression from tree-dwelling to bipedalism, highlighting the transition from our common ancestor with apes to the more human-like traits we see in later hominins.