Dr. Ian Toll, a researcher at the Institute for Biomedical Discovery Monash University, proposes folding nearly 5 million-year-old hominin fossils into this genus. Homo argues that traits once used to distinguish species (large brains, tool use) no longer apply.
Paranthropus boisei. Image credit: © Roman Yevseyev.
“Recent discoveries have undermined the usefulness and accuracy of current classifications, including current species in our own genus Homo, but also Australopithecus and Paranthropus. All lived within the past 5 million years,” Dr. Towle said.
“Discoveries and advances in evolutionary and genetic analysis make now an ideal time to reconsider whether our traditional taxonomy still accurately reflects human evolution.”
“These groups do not necessarily represent distinct evolutionary branches or clades, and the behavioral and ecological differences that were once used to distinguish the groups are also becoming increasingly difficult to maintain.”
“We propose to expand Homo by including these other groups in order to provide a more accurate and stable representation of the complex evolutionary relationships revealed by the growing fossil record.”
Dr. Towle argues that the current three-genus system taught in textbooks and museums no longer reflects what the fossil evidence actually shows.
He claims that Australopithecus, especially, is a group that has been repeatedly shown by phylogenetic studies to be non-monophyletic, meaning not composed of a single ancestor and all its descendants, contradicting standard modern biology’s definition of a valid group.
He also highlights how traits once thought to define human characteristics like brain size and tool use have been challenged by discoveries such as Homo naledi and Homo floresiensis. Although both species have small brains, they are classified in the same group as humans.
On the other hand, Australopithecus garhi has larger tooth size than Paranthropus, further blurring the boundaries between genera.
To support this claim, Towle compares modern primates, particularly baboons, with their relatives, and genetic studies have revealed extensive interbreeding between related genera.
He suggests that gene flow between closely related lineages tends to persist for millions of years after initial divergence, making the genus Homo particularly susceptible to instability due to its narrow definition in the past few million years.
Under his proposal, Homo, which dates back approximately 4 to 5 million years ago, is fixed at a branching point. He describes this node as one of the rare areas of consensus in paleoanthropology.
Hominins will be redefined as a pan-ethnic group, clade (including both chimpanzee and human lineages), and a new subtribe, Hominina, specifically for the human lineage.
Merging the three genera into one would erase distinctions that many researchers consider to be biologically meaningful, especially the differences between Homo and Paranthropus that followed different evolutionary and dietary pathways.
“Reclassifying” Australopithecus and Paranthropus species into the category of Homo will provide a more consistent understanding of our evolutionary history, uncover new fossils, and avoid continued redefinition as we learn more about our ancestors,” Dr. Towle said.
“The more we learn about our ancestors and fossil relatives, the more we realize how complex and non-linear our family tree is.”
Homo, which also includes the species of Australopithecus and Paranthropus, allows us to account for differences without constantly reclassifying specific groups.
Read the full paper in this week’s American Journal of Biological Anthropology.
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Ian Toll. 2026. The issue of clades, grades, and genera: The case for revising hominin taxonomy. American Journal of Biological Anthropology 190 (4): e70344;doi: 10.1002/ajpa.70344
Source: www.sci.news
