How the paleo diet worked for Lucy—and led to us

Evolution requires survival, and survival requires food. Information about what ancient creatures ate can unlock specific details about how and why they evolved, because not all foods are created equal. Some are dense in nutrients, but require knowledge, cooperation, or tools to access. Finding evidence for this in the fossil record can be challenging, because behavior doesn’t preserve. Other foods are easily available, but nutrient-poor. These often demand physical adaptations, such as large teeth and robust chewing muscles, that may be more obvious in a fossil. Lucy’s discovery shifted the spotlight of human origins research to eastern Africa, showing that the evolutionary group to which Lucy belonged lived in a wide range of habitats. This brought a new research focus to the ecology of our ancestors: paleoanthropologists wanted to know how our ancestors lived within their environments, not just how their bodies had changed over time.

For a long time, it was thought that Lucy’s kind were mostly vegetarians, eating diets similar to chimpanzees. But this view creates a puzzle, because chimpanzees do not live in the open habitats evidenced in the fossil record. Lucy’s skeleton also definitively showed how different these creatures were from chimpanzees: their lower bodies were built for striding around on two legs, and their back teeth were well-adapted for strong chewing. Lucy’s skeleton showed they had long arms, and fossils discovered later would reveal curved fingers that were surprisingly similar in proportion to human hands. Because nothing like Lucy had ever lived before, understanding how she lived and what she ate remains one of the most important ongoing challenges in paleoanthropology.

What we now know is that Lucy’s species was a wily omnivore, with a flexible diet that enabled our ancestors to venture into a broader range of environments than ever before. Discoveries in the last 15 years suggest that her larger evolutionary group made stone tools or even butchered large mammals hundreds of thousands of years before the first members of our own genus, Homo. This has caused researchers to carefully consider: when did the hallmarks of becoming human truly begin? Was it Lucy, with her taste for something different, that set us on the path to becoming ever smarter, more cooperative, and utterly dependent on tools? Future research will investigate these questions with new fieldwork, innovative approaches to reconstructing ancient diets, and a fresh theoretical perspective on what might have been possible.