What are the controversies surrounding the new homo naledi finds? What do they mean for the field of paleoanthropology and science communication in general? How do we move forward?
Homo naledi is a fascinating and mysterious species of ancient humans that was discovered in 2013 in the Rising Star cave system near Johannesburg, South Africa. The fossils, which belong to at least 15 individuals, have a mix of primitive and modern features, such as a small brain, curved fingers, and a human-like foot. The researchers who found them, led by palaeoanthropologist Lee Berger, have claimed that H. naledi is a new species that lived between 335,000 and 241,000 years ago, and that it deliberately buried its dead in deep chambers of the cave.
However, these claims have been met with sharp criticism and controversy from other experts in the field, who have questioned the validity of the new species designation, the evidence for intentional burial, and the dating of the fossils. Some have also accused Berger of rushing his findings to the public without proper peer review, and of creating a media circus that undermines the credibility of palaeontology.
In this blog post, I will examine some of the main points of contention and debate surrounding the new H. naledi finds, and discuss what they imply for the study of human evolution and the dissemination of scientific knowledge.
Is H. naledi a new species or not?
One of the most fundamental questions about H. naledi is whether it represents a distinct species or not. Berger and his colleagues have argued that H. naledi is different enough from other known hominins (the group that includes humans and their extinct relatives) to warrant a new species name. They have pointed out that H. naledi has a unique combination of traits that are not found in any other hominin, such as its small brain size (about 500 cubic centimeters), its slender body shape, its long legs relative to its arms, and its flared pelvis.
However, some critics have challenged this view, and have suggested that H. naledi is actually a variant of an already known species, such as Homo erectus or Homo heidelbergensis. They have argued that H. naledi’s traits are not so unique or unusual, and that they fall within the range of variation seen in other hominins. They have also pointed out that H. naledi’s skull shape and teeth are very similar to those of H. erectus, and that its small brain size could be explained by environmental factors or genetic drift.
The debate over H. naledi’s species status is not likely to be resolved anytime soon, as it depends on how one defines a species and how one interprets morphological data. There is no clear-cut criterion for determining what constitutes a species in palaeontology, and different methods can yield different results. Moreover, fossil evidence is often incomplete and fragmentary, making it difficult to compare different specimens and populations.
Did H. naledi bury its dead or not?
Another controversial issue about H. naledi is whether it intentionally buried its dead or not. Berger and his colleagues have proposed that H. naledi deliberately disposed of its deceased members in deep chambers of the Rising Star cave system, which they accessed through narrow passages that required climbing and crawling skills. They have based this hypothesis on several lines of evidence, such as:
– The absence of any signs of predation or scavenging on the bones
– The lack of any other animal remains or artifacts in the chambers
– The differences between the soil composition inside and outside the chambers
– The presence of articulated bones (bones that are still connected in their original position)
– The occurrence of etched symbols on some cave walls near the chambers
However, these lines of evidence have been contested by other researchers, who have offered alternative explanations for how the bones ended up in the chambers. Some have suggested that H. naledi’s bodies were washed into the chambers by water or mud flows, or that they fell into natural traps or pits. Some have also suggested that H. naledi’s bones were disturbed by later human activity or geological processes, or that they were artificially selected by Berger’s team based on their location.
The debate over H. naledi’s burial behavior is also unlikely to be settled soon, as it depends on how one interprets taphonomic data (the study of how fossils are formed and preserved). There are many factors that can affect the preservation and distribution of fossils in caves, such as water flow, sedimentation, erosion, bioturbation (the movement of animals or plants), human interference, etc. These factors can create complex and variable scenarios that are hard to reconstruct with certainty.
How old are H. naledi’s fossils?
A third contentious issue about H. naledi is how old its fossils are. Berger and his colleagues have estimated that H. naledi lived between 335,000 and 241,000 years ago, based on a combination of methods, such as uranium-thorium dating, electron spin resonance dating, and palaeomagnetic dating. They have argued that this age range is consistent with H. naledi’s morphology and phylogeny (its evolutionary relationship to other hominins).
However, some critics have questioned the accuracy and reliability of these methods, and have suggested that H. naledi’s fossils are much older or much younger than the estimated age range. Some have argued that the methods used by Berger’s team are prone to errors or contamination, or that they do not reflect the true age of the fossils, but rather the age of the sediments or minerals that surround them. Some have also argued that H. naledi’s morphology and phylogeny do not match its proposed age range, and that it should be either more primitive or more derived than it appears.
The debate over H. naledi’s age is also difficult to resolve, as it depends on how one applies and evaluates different dating techniques. There is no single method that can provide a definitive answer to the age of a fossil, and different methods can have different assumptions, limitations, and uncertainties. Moreover, dating results can be affected by various factors, such as sample quality, calibration, contamination, etc. These factors can introduce errors or discrepancies that need to be accounted for and explained.
What do these controversies mean for palaeoanthropology and science communication?
The controversies surrounding the new H. naledi finds have important implications for the field of palaeoanthropology and the communication of scientific knowledge in general. On one hand, they reflect the challenges and uncertainties that are inherent in studying human origins and evolution, which rely on limited and often ambiguous fossil evidence. On the other hand, they also reflect the diversity and dynamism of scientific inquiry and debate, which involve different perspectives, methods, and interpretations.
The controversies also highlight the need for transparency and openness in conducting and reporting scientific research, especially in a field that has a high public interest and impact. Berger and his colleagues have been praised for their innovative and collaborative approach to studying and sharing H. naledi’s fossils, which involved:
– Recruiting a large and diverse team of young researchers from around the world
– Publishing their results in an open-access journal with peer review comments
– Providing 3D files of their fossils for anyone to download and print
– Inviting feedback and criticism from other experts and the public
However, Berger and his colleagues have also been criticized for their sensationalist and premature presentation of their findings, which involved:
– Announcing their discoveries in press conferences and documentaries before peer review
– Making bold claims without sufficient evidence or consensus
– Ignoring or dismissing alternative hypotheses or interpretations
– Creating hype and confusion among the media and the public
The controversies thus raise questions about how to balance between speed and accuracy, between accessibility and quality, between outreach and rigor in scientific research and communication.
How do we move forward?
The controversies surrounding the new H. naledi finds are not likely to be resolved in the near future, as they require more data, analysis, and discussion. However, they also offer opportunities for advancing our understanding of human evolution and improving our practice of science communication.
To move forward, we need to:
– Collect more fossils of H. naledi from different sites and regions
– Apply more methods of dating, morphometrics (the measurement of shapes), genetics (the study of DNA), etc.
– Compare H. naledi with other hominins from different time periods and locations
– Test different hypotheses about H. naledi’s behavior, ecology (the study of interactions with the environment), culture (the study of learned behaviors), etc.
– Engage in constructive dialogue and debate with other researchers
– Publish our results in reputable journals with rigorous peer review
– Share our data and methods with other researchers and the public
– Communicate our findings in clear and accurate ways
– Acknowledge our uncertainties and limitations
– Invite feedback and criticism from other experts and the public
By doing these things, we can hope to gain a better picture of who H. naledi was, what it did, how it lived, when it died, and how it relates to us.
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