What the Dikika Discoveries Reveal About Human Origins

The Dikika research area in the Afar region of Ethiopia is a landscape of importance for paleoanthropology. Its sedimentary rock layers, exposed by the Awash River, represent a timeline stretching back more than four million years. This geological setting offers a window into the environments and life forms of our earliest ancestors. The research conducted here aims to uncover fossil evidence that helps piece together the story of human evolution.

The Discovery of Selam

In 2000, paleoanthropologist Zeresenay Alemseged, leading the Dikika Research Project, discovered a promising fossil. The specimen was largely encased within a sandstone block, presenting a challenge. Freeing the fossil required years of meticulous work to reveal the delicate bones held within.

Unveiling the Dikika Baby

After years of extraction, the fossil was identified as a complete skeleton of a juvenile female Australopithecus afarensis. Nicknamed “Selam,” the fossil is also referred to as the “Dikika Baby.” Scientific analysis dated the fossil to 3.3 million years ago, making her about 150,000 years older than the “Lucy” fossil of the same species.

At an estimated three years old at her death, Selam is the most complete skeleton of a juvenile human ancestor ever found. The find included most of the skull, the spinal column, ribs, and parts of both arms and legs. This completeness provides a detailed look at the anatomy of a young individual from this period.

What Selam Reveals About Human Ancestors

Selam’s skeleton offers a detailed picture of how Australopithecus afarensis moved. The structure of her leg and foot bones confirms that this species walked upright, a trait of the human lineage. This evidence for bipedalism helps in understanding our transition to walking on two legs.

However, her anatomy also shows features suited for a different kind of movement. Her shoulder blades were more ape-like than human-like, and her fingers were long and curved, suggesting she was also a capable climber. This combination of traits indicates that while her species walked upright on the ground, they likely still spent time in trees, perhaps for safety or to find food. This anatomical mix paints a picture of a species in transition.

Further analysis of the fossil yielded more insights. The discovery of her hyoid bone, a small bone in the neck that supports the tongue, provides clues about vocal capabilities. While not identical to that of modern humans, its structure opens up discussions about the potential for early forms of vocalization. Additionally, the size and development of her skull suggest that the brain grew slowly, a pattern more similar to human development than to that of chimpanzees.

Evidence of Early Tool Use

The Dikika site yielded another discovery, separate from the Selam fossil. In the same area, researchers found 3.4-million-year-old animal bones with distinct marks on them. These were not random scratches but cut marks made while carving meat from the bone and percussion marks from breaking bones to get to the marrow.

This evidence suggested that hominins, likely Australopithecus afarensis, were using stone tools much earlier than previously believed. The finding pushed back the estimated timeline for tool use by approximately 800,000 years. The discovery altered our understanding of the behavior of our early ancestors, suggesting they were butchering animals for food far earlier in their evolutionary history.