Possible Signatures of Hominin Hybridization from the Early Holocene of Southwest China

Abstract

We have previously described hominin remains with numerous archaic traits from two localities (Maludong and Longlin Cave) in Southwest China dating to the Pleistocene-Holocene transition. If correct, this finding has important implications for understanding the late phases of human evolution. Alternative interpretations have suggested these fossils instead fit within the normal range of variation for early modern humans in East Asia. Here we test this proposition, consider the role of size-shape scaling, and more broadly assess the affinities of the Longlin 1 (LL1) cranium by comparing it to modern human and archaic hominin crania. The shape of LL1 is found to be highly unusual, but on balance shows strongest affinities to early modern humans, lacking obvious similarities to early East Asians specifically. We conclude that a scenario of hybridization with archaic hominins best explains the highly unusual morphology of LL1, possibly even occurring as late as the early Holocene.

The Hybrid Origin of “Modern” Humans

“…This provides further confirmation that transgressive phenotypes and mosaic morphology are indeed signatures of hybridization in hominins, and opens the door for further investigation into the affinities of purported hybrids (e.g. Braüer 1981;Duarte et al 1999;Wolpoff et al 2001;Soficaru et al 2006;Rougier et al 2007;Ackermann 2010;Condemi et al 2013;Curnoe et al 2015) across the middleto-latest Pleistocene. Clearly fossil evidence for admixture is likely to be more widespread than we currently appreciate, a conclusion also supported by evidence for the prevalence of atypical traits in other hominin individuals (Wu et al 2013).…”

A Hominin Femur with Archaic Affinities from the Late Pleistocene of Southwest China

“…Several of the current authors have previously reported the occurrence of hominin cranial remains from two sites in Southwest China (Maludong and Longlin or Laomaocao Cave) that combine archaic hominin and AMH traits [ 24 , 25 ]. In the case of the unusual cranium from Longlin Cave [ 24 ], it was recently concluded that its mosaic morphology probably results from hybridisation between AMH and an unknown archaic species, perhaps even occurring during the early Holocene [ 26 ]. A similar explanation might also apply to the morphology of the Maludong cranial fossils [ 24 , 25 ], a hypothesis currently under investigation by us.…”

The geoarchaeology of hominin dispersals to and from tropical Southeast Asia: A review and prognosis

“…Furthermore, Late Pleistocene hominins with primitive morphologies from Southern China (e.g. Curnoe et al, 2010Curnoe et al, , 2015, and the metatarsal from Callao Cave dated to 67 ka (Mijares et al, 2010), that bears affinities with both modern humans and H. floresiensis, underscores the region as a melting pot of immigration and sporadic interbreeding (Pääbo, 2015). This implies that however bushy the Upper Pleistocene human family tree becomes, what is certain is that the reality of our evolution was most likely astonishingly complex.…”

“…Southern China is proving to be a rich source of Upper Pleistocene hominin fossils (Bae et al, 2014;Curnoe et al, 2012Curnoe et al, , 2015Liu et al, 2010Liu et al, , 2015. Nonetheless, archaeological research in this region has historically suffered from inadequate chrono-stratigraphic control.…”