Sometime around 55,000 years ago, a Neanderthal infant died in what is now Amud Cave in northern Israel. The child was only months old. But the bones and teeth it left behind tell a story that stretches far beyond one short life: this baby was growing faster than a modern human infant would at the same age, and it was not alone in doing so.
Across multiple peer-reviewed studies spanning three decades, researchers have found that Neanderthal infants hit physical developmental milestones, from tooth formation to skeletal hardening, on an accelerated schedule compared with Homo sapiens. The pattern, documented in fossils from Israel to Croatia, is reshaping how scientists understand the deep history of human childhood and why our species may have evolved to grow up so slowly.
The Amud Cave infant and what its bones reveal
The Amud infant, cataloged as Amud 7, was first described in 1994 by paleoanthropologists Yoel Rak, William Kimbel, and Erella Hovers in the Journal of Human Evolution. Their work confirmed the specimen as Neanderthal and established its morphology and preservation context, creating the scholarly foundation for everything that followed.
A subsequent analysis published in Current Biology went further, measuring multiple developmental indicators in the Amud 7 skeleton: rib and long-bone ossification (the process by which cartilage hardens into bone), endocranial volume, and the stage of dental eruption. By comparing these markers against known growth curves for modern human infants, the researchers estimated the child’s age at death and concluded that its physical development had outpaced what would be expected in a Homo sapiens baby of the same age. Because the full text of this study has not been widely accessible beyond its abstract, and the specific authors and publication year have not been confirmed in available sources, readers should treat the reported skeletal measurements as preliminary pending independent verification.
The finding did not emerge in isolation. It landed in a field already grappling with accumulating evidence that Neanderthal children developed on a different timetable than ours.
Krapina’s milk teeth tell a similar story
Roughly 1,500 miles northwest of Amud Cave, the Krapina rock shelter in Croatia has yielded Neanderthal fossils dated to between 120,000 and 130,000 years ago. Among them: deciduous teeth from three infants.
In 2021, a team led by Patrick Mahoney of the University of Kent published an analysis of those milk teeth in Proceedings of the Royal Society B. Using dental histology, a technique that reads microscopic daily growth lines preserved in enamel the way tree rings record a tree’s age, the researchers measured enamel formation timing, growth increments, and eruption sequences.
Their results were clear: prenatal tooth formation in the Krapina infants began earlier, and postnatal dental development proceeded faster, than in comparable modern human babies. A University of Kent summary of the research stated plainly that Neanderthal infant teeth developed sooner than those of living humans.
The Krapina findings matter in part because they come from a different site, a different time period, and a different research team than the Amud work, yet point in the same direction. In a field where sample sizes are tiny and individual fossils carry enormous analytical weight, that kind of independent convergence strengthens the case considerably.
Synchrotron studies and a lingering disagreement
High-resolution synchrotron imaging has added another layer of detail. Researchers at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, have used the technology to peer inside fossilized Neanderthal teeth at a microscopic level, measuring growth structures invisible to conventional methods.
One ESRF-based study, associated with work by Tanya Smith and colleagues on Neanderthal dental development, reported a root completion age of approximately 8.7 years and a predicted first molar eruption age of roughly 6.8 years in a Neanderthal specimen. Those numbers were initially interpreted as evidence that Neanderthal dental schedules broadly resembled modern human timelines, a conclusion that would complicate the faster-growth narrative.
But a separate study published in PNAS, also using synchrotron imaging and dental “birth lines” to compute precise ages at death, reached a different conclusion. After comparing maturation rates across Neanderthals and early modern humans, the authors argued that it is Homo sapiens who are the outliers, possessing a uniquely slow pattern of maturation rather than Neanderthals being unusually fast. As with the ESRF study, the specific authors, specimen identifiers, and publication year for this PNAS paper have not been confirmed in the sources available for this article, and readers should consult the primary literature for full attribution.
The tension between these findings reflects an active and unresolved debate. Both sets of results rest on small numbers of specimens, and the question of whether Neanderthals grew fast or modern humans grow exceptionally slowly is, in some sense, two ways of framing the same observation. What is not in serious dispute is that a developmental gap exists.
What researchers still cannot answer
Several significant gaps limit how far these conclusions can be pushed.
The taphonomic condition of the Amud 7 specimen, meaning how well the bones were preserved and whether burial, pressure, or mineral infiltration may have distorted growth markers, has not been formally reassessed since the original 1994 description. No study has yet produced comparative endocranial volume data linking the Amud and Krapina infants directly, and researchers must rely on indirect inferences when bridging skeletal and dental evidence across sites separated by tens of thousands of years and hundreds of miles.
More fundamentally, faster physical growth does not necessarily mean faster cognitive development. Brain organization, social learning capacity, and the transmission of cultural knowledge leave only faint and indirect traces in the fossil record. A Neanderthal infant whose bones hardened faster than a modern baby’s may or may not have reached behavioral or cognitive milestones on a similarly accelerated schedule. The two processes could have been decoupled in ways that bones and teeth alone cannot reveal.
There is also the question of variation within Neanderthals themselves. The current discussion often treats “Neanderthal growth” as a single species-wide pattern, but the fossils come from different regions, climates, and time periods. The individuals at Amud and Krapina likely experienced different diets, disease burdens, and environmental pressures. Without larger fossil samples from additional sites, it remains unclear whether the accelerated development seen so far reflects a broad life history strategy or a narrower adaptation shaped by local conditions.
Why slow growth may have been our species’ advantage
If Neanderthal infants really did grow faster, the obvious question is why Homo sapiens evolved in the opposite direction. Modern human children are strikingly slow to mature compared with nearly all other primates. Our brains take years to reach adult size. Our teeth erupt late. We remain physically dependent on caregivers far longer than our body size alone would predict.
Many researchers see that extended childhood as a feature, not a bug. A longer developmental window allows more time for the brain to wire itself through experience, for children to absorb complex social and cultural information, and for caregiving networks to invest in each child’s survival. Some evolutionary models tie this pattern to the “grandmother hypothesis,” which proposes that post-reproductive adults in human groups helped provision slow-growing children, enabling the species to sustain a longer, more resource-intensive childhood than would otherwise be viable.
By contrast, rapid early growth in Neanderthals may have been an adaptation to harsher, less predictable Ice Age environments, where reaching physical independence quickly could mean the difference between surviving a lean winter and not. But that speed may have come with trade-offs: less time for the kind of prolonged social learning that appears to underpin the cultural complexity Homo sapiens eventually developed.
As of May 2026, this remains a hypothesis rather than a settled conclusion. But the accumulating fossil evidence, from Amud Cave to Krapina to synchrotron labs in France, is making the developmental gap between the two species harder to dismiss. Each new specimen and each higher-resolution scan brings researchers closer to understanding not just how quickly Neanderthal children grew, but what our own species gained by growing up slowly.
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*This article was researched with the help of AI, with human editors creating the final content.
