The evolution of the human beard

146 ABSTRACTS / HOMO - Journal of Comparative Human Biology 64 (2013) 142–162

The endosteal region of long bone shafts: A potential area of difference between human andnon-human bones

S. Croker*, W. Reed, D. Donlon (University of Sydney, Sydney, Australia),scroker@anatomy.usyd.edu.au

Identifying bone as human or non-human is important in forensic and archaeological cases. Struc-turally, all mammal bone shares several similarities, making identification of bone fragments difficult.During the course of a project involving the analysis of radiographs of human and non-human longbones, comparative differences in the radiographic appearance of the endosteal border and medullarycavity were noticed. Very few researchers have described radiographic differences between humanand non-human bones, but those that have indicate promising results. The preliminary findingspresented here also suggest that this may be a useful area in which to differentiate human fromnon-human bone. In radiographs, the endosteal border of the human bones was rough and indistinct,in contrast to the usually smooth, sharp border in non-human bones. The medullary cavity showedstreaks and opacities in human bones, yet was much clearer in non-human bones. Examination ofactual sectioned bones revealed the endosteal surface to be generally much smoother in non-humanbones. In human bones, the medullary cavity frequently contained an irregular network of trabecularbone, accounting for the patterns observed in the radiographs. With further research, this could be auseful aid in the identification of bone fragments.

http://dx.doi.org/10.1016/j.jchb.2013.02.011

The evolution of the human beard

B. Dixson* (University of New South Wales, Sydney, Australia), P. Vasey (University of Lethbridge),R. Brooks (University of New South Wales, Sydney, Australia),b.dixson@unsw.edu.au

The beard is arguably the most strikingly sexually dimorphic trait in humans, yet the role of facialhair in determining men’s socio-sexual attributes is unresolved. The artificial or natural stimulus setschosen and a lack of cross-cultural data likely contribute to the equivocal nature of past findings.We used natural photographs of men varying in beardedness, posing with standardized pleasantand threatening facial expression, to test the role of beards in determining a suite of socio-sexualattributes. Data were collected among men and women in New Zealand and Samoa (Study 1) andamong participants in on-line survey (Study 2).

Participants from New Zealand and Samoa rated beards as looking older and as having highersocial status than the same men when clean-shaven. We also found that men posing with angry facialexpressions were perceived as more threatening when bearded. However, in both cultures womenrated clean-shaven male faces as more attractive than bearded faces. In Study 2 we confirmed that fullbeards were not rated as most attractive. However, they were judged as looking the healthiest, mostmasculine and as being better parents than clean-shaven faces. These findings are consistent withthe hypothesis that the human beard is involved in intra-sexual communication of status and threat.While beards do not augment male facial attractiveness, their strong value in intra-sexual signaling,coupled with positive associations regarding resource acquisition and social maturity, may explainwhy men with full beards were perceived as better fathers who would protect and invest in offspring.

http://dx.doi.org/10.1016/j.jchb.2013.02.012