3.3 Million Year Old Vertebral Column Confirms Human Pattern of Au. afarensis

The science site PhysOrg has posted a story on a study of the 3.3 million year old fossil from the site of Dikika, in the Afar Triangle.  The fossil, known as Selam, is an almost complete skeleton of a 2 ½ year-old child. From the story:

Many features of the human spinal column and rib cage are shared among primates. But the human spine also reflects our distinctive mode of walking upright on two feet. For instance, humans have fewer rib-bearing vertebrae - bones of the back - than those of our closest primate relatives. Humans also have more vertebrae in the lower back, which allows us to walk effectively. When and how this pattern evolved has been unknown until now because complete sets of vertebrae are rarely preserved in the fossil record.

"For many years we have known of fragmentary remains of early fossil species that suggest that the shift from rib-bearing, or thoracic, vertebrae to lumbar, or lower back, vertebrae was positioned higher in the spinal column than in living humans. But we have not been able to determine how many vertebrae our early ancestors had," said Carol Ward, a Curator's Distinguished Professor of Pathology and Anatomical Sciences in the University of Missouri School of Medicine, and lead author on the study. "Selam has provided us the first glimpse into how our early ancestors' spines were organized."

This gives us much better evidence of how bipedality was practiced in some of the earliest hominins. We know, from the footprints at Laetoli and the hip remains of Lucy, that Au. afarensis was bipedal but now we know that the rib structure had evolved into a more human pattern.