Evidence of interbreeding between archaic and modern humans – or just highly diverse morphology?

50,000-year-old Tam Pa Ling lower jawbone is a mosaic of archaic and modern features

Tam Pa Ling (‘Cave of the Monkeys’) is a cave site in Huà Pan Province, Laos. A fully-modern partial human skull (TPL1) was recovered in December 2009, followed a year later by a complete human lower jawbone (TPL2). The upper jawbone of TPL1 does not match with TPL2, so the two represent different individuals. The fossils are estimated to be from 46,000 to 63,000 years old, establishing an early presence of modern humans in Southeast Asia.

A newly-published study of the more recent discovery suggests that the TPL2 lower jawbone, though essentially modern, possesses a number of archaic attributes. The most obvious sign of modern affinities is the clear presence of a chin. However, viewed from the side, the jawbone is very robust, particularly at the position of the first and second mandibles. In this respect, TPL2 is closer to the archaic than the modern human condition.

While this mosaic could be evidence of modern humans interbreeding with archaic populations – possibly Denisovans or Homo erectus – the authors of the report take the view that early modern humans in the region simply possessed a large range of morphological variation.

Reference:

x

Demeter, F. et al., Early Modern Humans and Morphological Variation in Southeast Asia: Fossil Evidence from Tam Pa Ling, Laos. PLoS One 10 (4), e0121193 (2015).x