Did Neanderthals die out before modern humans reached southern Europe?

Study casts doubt on late Neanderthal survival in Iberian Peninsula.

Until fairly recently, it was believed that Neanderthals and modern humans coexisted in Europe for up to 10,000 years, but recent improved radiocarbon dates suggest that this period was far shorter – possibly no more than 1,000 or 2,000 years (Mellars, 2006). Many supposedly-late Neanderthals have now been shown to be much older than first believed. For example, two specimens from Vindija Cave in Croatia were originally thought to be from 32,000 to 33,000 years old (28,000 to 29,000 radiocarbon years BP) (Smith, et al., 1999), but these dates are now thought to be nearer 36,000 to 37,000 years old (32,000 to 33,000 radiocarbon years BP) (Higham, et al., 2006). Similarly, an infant from Mezmaiskaya Cave in the northern Caucasus, once believed to be a late survivor from 29,000 years ago, is now believed to be have lived more like 40,000 years ago (Pinhasi, et al., 2011).

Another factor is that calendar dates from this period might have been systematically underestimated. Radiocarbon dates do not coincide exactly with calendar dates, and the latter must be estimated using calibration data. A recent re-evaluation suggests that the estimated calendar dates for this period should be older than was previously believed. The revised dates suggest that overall, the period of coexistence between Neanderthal and modern human populations within the individual regions of Europe such as western France was fairly brief, possibly no more than 1,000 or 2,000 years (Mellars, 2006).

At the peripheries of Europe, Neanderthals might have persisted for rather longer than elsewhere. Possible late survival is documented from two very different settings: Gorham’s Cave, Gibraltar, and Byzovaya, in the western foothills of the northernmost Urals. Gorham’s Cave seems to have been a favoured location that was visited repeatedly over many thousands of years. Natural light penetrates deep into the cave, and a high ceiling permits ventilation of smoke from the hearths that were repeatedly made there. Neanderthal occupation of the cave continued until 33,000 years ago (28,000 radiocarbon years BP), and possibly until as recently as 29,000 years ago (24,000 radiocarbon years BP), and the site was later used by modern humans right up until Phoenician and Carthaginian times. However, there was a 5,000 years hiatus after the last Neanderthal occupation before the first modern humans took up residence (Finlayson, et al., 2006; Finlayson, et al., 2008). At Byzovaya, a total of 313 stone artefacts have been collected over the years, all reflecting typical Middle Palaeolithic tool production techniques characteristic of Neanderthal Mousterian industries, and ranging from 31,000 to 34,000 years old (Slimak, et al., 2011).

However, a newly-published study has cast doubt on the late Neanderthal survival in the Iberian Peninsula. Researchers used a technique known as ultra-filtration to remove traces of modern contaminants (for example preservatives and glues) from fossil bone collagens (proteins making up the bone matrix) prior to radiocarbon dating. Without this process, it is claimed that the contaminants make samples appear younger than they actually are. For example, a carbon contamination of just one percent will make a 50,000-year-old sample appear to be just 37,000 years old. A total of 215 Neanderthal bones from 11 supposedly-late Neanderthal sites were screened for collagen. Unfortunately, only 27 bones were found to contain enough collagen for radiocarbon dating using the ultra-filtration technique. These were recovered from just two sites: Jarama VI and Cueva del Boquet Zafarraya. The results suggested that the Neanderthal remains from the two sites were at least 10,000 years older than previously believed (Wood, et al., 2013). Should other dates for the Iberian Neanderthals turn out to have been similarly understated, then it would suggest that they died out before modern humans arrived. However, it should be noted that the authors of the Gorham’s Cave report had previously considered and ruled out the possibility of contamination affecting their results (Finlayson, et al., 2008).

References:

1. Mellars, P., A new radiocarbon revolution and the dispersal of modern humans in Eurasia. Nature 493, 931-935 (2006).

2. Smith, F., Trinkaus, E., Pettitt, P., Karavanic, I. & Paunovic, M., Direct radiocarbon dates for Vindija G1 and Velika Pecina Late Pleistocene hominid remains. PNAS 96 (22), 12281–12286 (1999).

3. Higham, T., Ramsey, C., Karavanic, I., Smith, F. & Trinkaus, E., Revised direct radiocarbon dating of the Vindija G1 Upper Paleolithic Neandertals. PNAS 103 (3), 553–557 (2006).

4. Pinhasi, R., Higham, T., Golovanova, L. & Doronichev, V., Revised age of late Neanderthal occupation and the end of the Middle Paleolithic in the northern Caucasus. PNAS 108 (21), 8611-8616 (2011).

5. Finlayson, C. et al., Late survival of Neanderthals at the southernmost extreme of Europe. Nature 443, 850-853 (2006).

6. Finlayson, C. et al., Gorham’s Cave, Gibraltar - The persistence of a Neanderthal population. Quaternary International 181, 74-71 (2008).

7. Slimak, L. et al., Late Mousterian Persistence near the Arctic Circle. Science 332, 841-845 (2011).

8. Wood, R. et al., Radiocarbon dating casts doubt on the late chronology of the Middle to Upper Palaeolithic transition in southern Iberia. PNAS 110 (8), 2781-2786 (2013).