3.3-million-year-old fossil reveals origins of the human spine

Recent analysis of a 3.3-million-year-old hominin fossil has provided researchers with the most complete spinal column of any early human relative.

The analysis offers a unique snapshot of a crucial transition point as humans’ early ancestors evolved towards bipedalism.

The findings were published in the journal Proceedings of the National Academy of Sciences.

The fossil, known as Selam, is a nearly complete skeleton of a two-and-half-year-old child discovered in Dikika, Ethiopia, in 2000. Selam was an early human relative from the species Australopithecus afarensis. Selam means peace in the Ethiopian Amharic language.

Key highlights of the analysis

• The research shows that the general structure of the human spinal column emerged over 3.3 million years ago.

• The fossil provided the first glimpse into how humans’ early ancestors’ spines were organised.

• At the European Synchrotron Radiation Facility in Grenoble, France, the research team used high-resolution imaging technology to visualise the bones of Selam.

• The scans indicated that Selam had the distinctive thoracic-to-lumbar joint transition found in other fossil human relatives. The specimen is the first to show that, like modern humans, our earliest ancestors had only twelve thoracic vertebrae and twelve pairs of ribs. That is fewer than in most apes.

• This unusual early human configuration may be a key in developing more accurate scenarios concerning the evolution of bipedality and modern human body shape.

• This configuration marks a transition toward the type of spinal column that allows humans to be the efficient, athletic walkers and runners.