On the enamel of fossilized teeth lying in African soil for millions of years, scientists have discovered something small but possibly earth-shaking: tiny, uniform pits grouped in patterns too uniform to be coincidence, too faint to be scars. These shallow punctures, found primarily in back molars, may redefine the way we interpret the ancient history of human evolution.
The new study, in The Journal of Human Evolution, not only points to a biological peculiarity — it suggests a genetic signature for an entire extinct genus: Paranthropus, from 2.2 million years ago!
Pitting these Problems: Disease or Stress?
These pits of enamel are not new to science. For decades, paleoanthropologists attributed them to malnutrition or childhood disease early in life — stress-induced breaks in enamel development in tooth growth. But this recent study, conducted by Ian Towle at Monash University, turns that conception on its head.
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Uniform, circular, and shallow pitting on two Paranthropus robustus teeth from Drimolen Main Quarry, southern Africa. (Towle, et al., Journal of Human Evolution, 2025)
What the researchers discovered was surprisingly consistent: uniform, round, and shallow pits (UCS, for short), occurring in a predictable pattern on the chewing surfaces of Paranthropus molars. They were intentional — at least from an evolutionary perspective!
"Teeth preserve an incredible amount of biological and evolutionary information," study co-author Ian Towle, a researcher in the Palaeodiet Research Lab at Monash University in Australia, told Live Science. "This specific type of pitting might turn out to be a unique marker for certain evolutionary lineages, helping us identify fossils."
And they weren't ubiquitous.
The UCS pattern was present in both eastern and southern African Paranthropus fossils, such as South Africa's Drimolen and Swartkrans, and Ethiopia's Omo Valley. But the pitting was virtually nonexistent in Homo (our genus), and unexpectedly uncommon in Australopithecus africanus, previously considered to be Paranthropus's immediate ancestor.
That's an important detail. It implies Paranthropus diverged earlier than we have believed, maybe from East African australopithecines instead of southern ones. The pits might be the dental reflection of a divergence in the family tree.
Paranthropus enamel pitting on three different molars. (Towle, et al., Journal of Human Evolution, 2025)
Likely Genetic: An Elusive Functionary Purpose
What is so interesting about this pitting is how it acts. It doesn't occur according to patterns of stress. It's not related to tooth size, not randomly scattered, and not occurring in all teeth — just in molars. That suggests a developmental characteristic, rather than an imperfection.
Towle and his colleagues made a contemporary comparison: amelogenesis imperfecta, a genetic disorder that affects enamel in about 1 in 1,000 individuals today. Certain forms of it can lead to similar pitting in teeth in modern human beings. But in Paranthropus, these pits appear in as many as 50% of the individuals.
"It's likely genetic," Towle wrote in The Conversation. "It might even have had a functional purpose we hadn't grasped yet."
If UCS pitting is heritable, it's more than an evolutionary aside — it's a potential taxonomic marker. Just as the thickness of enamel, the form of cusps, and patterns of wear distinguish species for paleoanthropologists, these pits in the enamel could be a new diagnostic measure.
They provide a line of evidence entirely independent of bone morphology or DNA (which seldom clings to life in hot, damp African soils). And in an area of work where speciation often involves sorting out infinitesimal anatomical distinctions, another resource is no small matter.
This also lends credibility to the concept of Paranthropus being a monophyletic group — that its species came from a common ancestor, and did not evolve separately in various locations. UCS pitting, observed through time and space, attests to that.
A Hobbit-Sized Puzzle
One of the most suggestive facts in the study: the same pitting might be found in Homo floresiensis, the "hobbit" species from Indonesia. It could widen the likelihood that H. floresiensis has evolutionary connections with older Australopithecine species and not the primary Homo line.
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But that's still conjectural. As the scientists point out, H. floresiensis teeth also exhibit evidence of other pathologies, and information is scarce. More study must be done before lines can be drawn between species based on pits alone.
This finding — small as it may be — contributes another thread to our knowledge of how human ancestors developed. It makes the neat branching trees more complicated and encourages us to see beyond bones and genomes. Evolution sometimes leaves its marks in dimples and spots on the very teeth that ground the ancient world.
Examples of enamel hypoplasia and other dental defects, as well as purely morphological features that somewhat resemble but are not UCS pitting, in hominin and nonhuman primate samples. (Towle, et al., Journal of Human Evolution, 2025)
For Towle and his crew, UCS pitting serves as a tool, a clue, possibly even a signature.
Top image: The original complete skull (without mandible) of a 1,8 million years old Paranthropus robustus discovered in South Africa Source: Ditsong National Museum of Natural History/CC BY-SA 4.0
By Sahir
References
Killgrove, K. 2025. Strange pits on 'hobbit' teeth and other archaic humans could reveal hidden links in our family tree. Available at: https://www.livescience.com/archaeology/human-evolution/strange-pits-on-2-million-year-old-teeth-may-reveal-which-human-relatives-are-closely-related-to-each-other.
Towle, I. 2025. 2-million-year-old pitted teeth from our ancient relatives reveal secrets about human evolution. Available at: https://theconversation.com/2-million-year-old-pitted-teeth-from-our-ancient-relatives-reveal-secrets-about-human-evolution-258390.
Towle, I., et al. 2025. Uniform, circular, and shallow enamel pitting in hominins: Prevalence, morphological associations, and potential taxonomic significance. Journal of Human Evolution, 205. Available at: https://doi.org/10.1016/j.jhevol.2025.103703.
