The 85th Annual Meeting of the American Association of Physical Anthropologists (2016)

Using extant taxa to model variation in hominin hybrid populations


1Department of Archaeology, University of Cape Town, 2Department of Anthropology, University at Buffalo, 3School of Human Evolution and Social Change, Arizona State University, 4Department of Cell Biology and Anatomy, University of Calgary

April 14, 2016 11:15, Imperial Ballroom B Add to calendar

Current models of hybridization based on mouse and baboon skeletons indicate extreme cranial size and size-related shape (or heterosis) for first generation (F1) hybrids compared with their parents, an intermediate-to-parental cranial shape, and occasionally the presence of transgressive phenotypes. However, the likelihood of an F1 hybrid being discovered in the hominin fossil record is small, making the application of such single-generation models to understanding and detecting hybridization in the hominin fossil record limited. Here we use various hybrid and purebred mouse strains combined with resampling-based modelling to explore the range of variation likely to be present in a multigenerational recombinant hybrid zone. 95% confidence intervals of means and variances for potential mixed groups are determined to better understand what to expect in a mixed population or hybrid swarm. Results indicate that F2 hybrids are intermediate to F1s and parents, although >80% more closely resemble F1s. Backcrosses and subsequent generations are more likely to exhibit a parental phenotype. However, considered in a multigenerational context, when 35% of individuals in a population exhibit some degree of admixture, the population has significantly greater average cranial size and variance than that of the pooled parental populations. Results are consistent with morphology of the Oase 1 mandible, a known recombinant with Neanderthal ancestry (4-6 generations prior), which nonetheless is more similar to Early Upper Palaeolithic modern humans. Examination of metric and non-metric trait variation in the Krapina Neanderthals also reveals a suite of features consistent with the model presented here for a hybrid population.

This research is funded by the DST/NRF Centre of Excellence in Palaeosciences (CoE-Pal) and the National Research Foundation of South Africa