The mystery of Neanderthal's disappearance

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The main body of the chapter has already presented several avenues put forward to explain Neanderthal’s disappearance: Thomas Higham’s redating, competition with Homo sapiens, the Campanian Ignimbrite volcanic hypothesis, and the cultural debate over the Grotte du Renne. Two questions, however, remain to be explored further: the species’ inherent demographic fragility, and the persistent difficulty of identifying its last representatives with certainty.

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🧬 The demographic hypothesis: a genetically fragile species

Beyond external factors, Neanderthal itself seems to have carried a structural fragility. Estimates place the species’ effective population at only about 3,000 individuals, spread across small groups scattered throughout Eurasia. In 2017, the complete sequencing of the genome of a Neanderthal woman from Vindija cave, in Croatia, who lived 55,000 years ago, published in the journal Science by researchers at the Max Planck Institute, confirmed an overall low genetic diversity, characteristic of the species as a whole.

The picture, however, remains nuanced: this same Vindija woman showed a lower level of inbreeding than other already-sequenced Neanderthal individuals, comparable to that of certain isolated indigenous populations of the Americas today — which rules out speaking of a uniform, generalized demographic collapse. It is precisely this Vindija genome, closer to the population that actually interbred with Homo sapiens, that made it possible to re-evaluate the Neanderthal contribution to modern humans’ genetic makeup, raised to 1.8–2.6%.

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🗺️ The debate over the “last Neanderthals”: Zafarraya and Gorham’s Cave

Identifying Neanderthal’s last stronghold remains, moreover, a task fraught with pitfalls. The site of Zafarraya, in Spain, was long presented as a late refuge, with dates falling between 33,400 and 28,900 years ago. A new round of measurements using ultrafiltration, however, pushed back the age of a goat bone from the site, previously estimated at 33,300 years, to more than 46,700 years — ruining the hypothesis of a particularly late survival at this location.

The case of Gorham’s Cave, in Gibraltar, illustrates a similar difficulty: a series of twenty-two radiocarbon dates, published in 2008, suggested Neanderthal occupation there until around 24,000 years ago, which would have made it by far the latest known site for the species. This interpretation is now widely contested, owing to the microscopic size of the dated samples, the wide scatter of the results, and the absence of any correlation between the age obtained and stratigraphic depth. The late survival of Neanderthal in southern Iberia thus no longer rests, in the current state of knowledge, on more than a single site judged genuinely reliable, that of Cueva Antón — a reminder that the chronology of the species’ disappearance remains, even today, an active field of research.

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🧠 Key points

• Neanderthal’s effective population is estimated at only ~3,000 individuals, with overall low genetic diversity
• The genome of the Vindija woman (2017, ~55,000 years ago) nuances the idea of a uniform demographic collapse: her level of inbreeding was lower than that of other Neanderthal specimens
• Zafarraya (Spain), long presented as a late refuge, was redated to more than 46,700 years ago, invalidating this hypothesis
• Gorham’s Cave (Gibraltar), which suggested survival until -24,000, is the subject of serious methodological challenge
• Cueva Antón remains the only site judged reliable for a late Neanderthal survival in Iberia