Where does Homo naledi fit into our family tree?

Researchers discuss the startling age of the Homo naledi bones and thoughts on how the bones came to be in the Rising Star cave system.

Vocabulary: hominin, evolution, paleoanthropology, evolutionary tree

Next Generation Science Standards: LS4.A: Evidence of Common Ancestry and Diversity, CC1: Patterns, and SEP7: Engaging in Argument from Evidence. Can be used to build towards the following performance expectionations: MS-LS4–1, MS-LS4–2, and HS-LS4–1.

Common Core State Standards: CCSS.ELA-LITERACY.RST.6–8.8, CCSS.ELA-LITERACY.RST.9–10.8

A composite skull of Homo naledi constructed by Prof. Peter Schmid. Courtesy of the University of the Witwatersrand and the Dinaledi project provided access to these data originally appearing in. The files were downloaded from www.MorphoSource.org, Duke University.

Two years ago, scientists announced a puzzling find inside a South African cave: 1,500 bones, representing what they identified as a new hominin species, Homo naledi. The bones came from 15 different individuals and had a mix of primitive and modern features. At the time, the researchers didn’t know the age of the bones.

‘’Neo’’ skeleton of Homo naledi from the Lesedi Chamber. Photo credit: Wits University/ John Hawks

This week, the team revealed that the fossils of Homo naledi are between 335,000 and 236,000 years old, meaning that Homo naledi and early humans could have roamed Africa during the same time period. The bones were found in a chamber deep inside of the cave.

The group also announced this week that they had found a second chamber that contained fossils of two adults and one child.

The Rising Star cave system is cramped, so it requiring a team of smaller-sized paleontologists. Dr Marina Elliott [one of the team leaders] inside the Rising Star cave system. Credit: Dirk van Rooyen/ Wits University

Paleoanthropologist John Hawks, a member of that team, and anthropologist Susan Anton, who was not involved in the research, discuss how these discoveries change our understanding of the human family tree. They also explain what signs would indicate that these remains were intentionally interred inside of the cave.

Audio Excerpt “Ancient Homo Naledi May Have Walked Alongside Early Humans,” May 12, 2017. (Original Segment)

Print this segment transcript.

Questions

  • Why do you think John Hawks and his team had the bone samples tested so rigorously? Why do you think independent evaluation and testing are important steps to take in this investigation?
  • Why is Homo naledi considered a “rewrite the textbook” find? How does it change the way we connect the branches on the human evolutionary tree?
  • What evidence would you expect to see on bones if they were deposited by predators? What evidence would indicate they were moved there by water? What evidence would suggest they were dropped through an opening in the top of the cave?
  • What is a null hypothesis? Why do you think that it is usual to start with the assumption that the bones were deposited naturally? Explain whether you agree with Susan Anton’s premise.
  • John Hawks and his team are suggesting that the Homo naledi bones were deposited in intentional burials. What would this suggest about Homo naledi behavior or culture? What further evidence might help researchers determine whether these were intentional burials?

Activity Suggestions

Frontal view of the “Neo” skull of Homo naledi from the Lesedi Chamber. Photo credit: Wits University/John Hawks

Additional Resources