Question

comment on earliest people
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Answer 1

Answer:

minimum age of no more than ~60,000 to 70,000 years.

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Misliya-1, part of the maxilla of an anatomically modern human from Misliya Cave, Israel, was assigned an age of 177 to 194 thousand years (ky) (1). Methods using U-series disequilibrium to date the fossil included combined U-series and electron spin resonance (US-ESR) on tooth enamel, laser-ablation 230Th/U dating of dentine, and 230Th/U dating of soil carbonate encrusting the maxilla. The US-ESR age estimate of 174 ± 20 ky (all errors 2σ) was considered a maximum age because the fossil was irradiated during three computed tomography scans prior to dating (1). Laser spots across a section of dentine yielded broadly consistent 230Th/U age estimates between 83 ± 9 and 62 ± 3 ky. A 230Th/U age estimate of 185 ± 8 ky on soil carbonate was interpreted as a minimum age for the fossil; however, that date is not supported by the U-series data in (1).

A reported age of 185 ± 8 ky for crust sample Maxilla-6 is crucial to the central claim of Hershkovitz et al., but that sample has clearly failed to maintain a closed U-series system. The authors erroneously reported an uncorrected age of “equilibrium” for Maxilla-6 [table S2 of (1)]. In fact, Maxilla-6 has an uncorrected 230Th/234U activity ratio greater than 1.0, indicating an excess of 230Th over its parent 234U (2). This condition is commonly produced when materials lose uranium relative to thorium after deposition, thereby violating a fundamental premise of radiometric dating. We contend that the reported age for Maxilla-6 was obtained by incorrectly computing detritus-corrected U-series isotope ratios, as described below.

Explanation:

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