In the US, Mother’s Day is this Sunday, so I thought it appropriate to introduce this fine specimen, representative of what many Paleo-anthropologists consider the earliest known mother of all hominids (including us Homo sapiens). This is the Ardipithecus ramidus, and she lived about 4.4 million years ago in what is now modern Ethiopia. Her fossils were discovered in 1994, but it wasn’t until 2009 that analysis of her bone structure suggested that she was an ancestral species of ours which was transitioning to bipedalism.
You can see that “Ardi'” (that is her nickname in scholarly circles) doesn’t look particularly human in her face, and indeed, she had many similarities with primitive tree-dwelling primates. She only stood about four feet tall (120 cm) and weighed about 110 lbs (50kg). But many scholars argue that her bones show a path towards true upright walking: her skull rested atop her neck instead of forward; her big toes — although separated from her feet like our own fingers are separated from our thumbs — were parallel to our other toes; her hands and wrist bones were able to carry and grasp objects; and her pelvis shape suggests that her gluteal muscles were positioned in a way that allowed balancing on one leg, and thus made walking, easier.
Champions of Ardi’s proto-bipedalism argue that she would have lived in the trees but also could have walked upright on the ground for short distances. This would have enabled her to take advantage of gathering food from both woodland and savannah, an ecosystem that had recently developed in her part of Africa. This, she might have been an ancestor of the Australopithecus afarenais, of the “Lucy” fame.
Sources: Case Western Reserve, _the daily_, “New findings shed light on origin of upright walking in human ancestors,” April 1, 2019. Smithsonian National Museum of Natural History, “What does it mean to be human”? Ardipithecus ramidus
