Friday, 1 March 2013

Doubt cast on Tam Pa Ling age

For reference, see the post on the original article:
  • Tam Pa Ling: modern humans in Southeast Asia at 63-46ka

From a criticism of the original paper:

Hence, contrary to the authors' assertion that TPL1 has a “minimum secured age of 46 ka and a maximum age of ∼63 ka”, the published stratigraphy, if correct, indicates that the TPL1 specimen is no older than 46 ka. TPL1’s status as “the earliest well-dated modern human fossil east of the Jordan Valley” also appears weak compared with the Liujiang specimen dated to ∼153 ka (3), the Callao Cave fossil in the Philippines dated to 67 ka (4), and, above all, the ∼100 ka modern fossil from Zhirendong (5), discovered only 484 km northeast of Tam Pa Ling in Southern China.

Irreconcilable differences between stratigraphy and direct dating cast doubts upon the status of Tam Pa Ling fossil

Alain Pierret et al.


... and from a reply to the criticism by the authors:

They question the validity of the dating because of an apparent “reverse stratigraphy” (Fig. 1), whereby “older” dates are located higher in the section [i.e., 51.4 (14C) at 2.1 m] and “younger” dates are at the bottom of the section [i.e., 48 ka (optically stimulated luminescence [OSL]) and >49.2 ka (14C) at 4.3 m] (2). This criticism ignores the presented SEs (table 2 and table S1 in ref. 1), which make the results statistically equivalent (Table 1). More importantly, they ignore that the radiocarbon results are well beyond the accepted radiocarbon barrier of ∼40 ka (3), indicating that the charcoal has a minimum age of ∼40 ka. Bearing in mind these problems, we have conservatively estimated the burial age to be ∼46 ka according to the luminescence dating of the sediments. As the luminescence results are stratigraphically consistent, we perceive no irreconcilable differences between the stratigraphy and dating.
Finally, we interpret TPL1 as the earliest human fossil that is both well-dated and fully modern in morphology. Zhirendong demonstrates a mixture of archaic and modern traits, making it significant but not fully modern in appearance (4). Similarly, the metatarsal from Callao Cave is only diagnostic to the genus Homo given that it falls within “the morphological and size ranges of Homo habilis and H. floresiensis” (ref. 5, p. 123). Although the modernity of the Liujiang fossil is not questioned, it has no direct date and no secure stratigraphic provenance. It has been variably dated to ca. 20 ka, ca. 67 ka, 111 to 139 ka, and >153 ka (6), and this uncertain stratigraphic context has prevented many scholars from accepting any of the dates currently attributed to it (6).

Reply to Pierret et al.: Stratigraphic and dating consistency reinforces the status of Tam Pa Ling fossil

Fabrice Demeter et al.


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