A new experimental study from Australia provides the first direct evidence that penis size, height, and a V-shaped torso significantly influence the assessment of male sexual attractiveness and perceived physical fighting ability. The research, published in PLOS Biology on January 22, 2026, is based on the evaluation of 343 computer-generated male figures by over 800 participants of both sexes.
The figures systematically varied in three characteristics: penis size (small, medium, large), height (short, average, tall), and torso shape (V-shape with broad shoulders and narrow waist vs. less pronounced V-shape). The animations were presented either life-size on-site or to scale online. Participants rated the figures for sexual attractiveness (female participants) and sexual competitiveness and physical threat (male participants).
The results show consistent directional selection:
- Larger penis size was rated as more sexually attractive by women, and as more sexually competitive and physically threatening by men.
- Greater height and a more pronounced V-shaped torso also received higher ratings in both categories.
The study used selection gradient analyses to quantify the strength and direction of preferences. The effects persisted even after controlling for intercorrelations between the traits. Particularly striking was the agreement between female attractiveness ratings and male assessments of rivalry: traits that women found more attractive were simultaneously perceived by men as a greater threat.
The authors interpret the findings evolutionarily: penis size, height, and V-shaped torso may have been jointly positively selected through female mate choice and male competition. This would explain why humans possess an exceptionally large penis compared to other primates – a trait that has been controversially discussed in the literature for decades. To the authors' knowledge, the study is the first experimental work to isolate and investigate penis size as an independent factor in the assessment of male competitiveness and attractiveness.
Methodologically, great emphasis was placed on realism and control. The figures were created using professional 3D modeling software and presented in a standardized pose. To exclude confounding factors from facial attractiveness, the faces were kept neutral and blurred. Ratings were made on 7-point Likert scales. The consistency of the results between live and online presentation underscores the robustness of the findings.
The work is part of a longer research tradition that investigates physical characteristics and their role in sexual selection. Previous studies had already shown that height and shoulder-to-waist ratio are strong predictors of attractiveness. What is new is the experimental evidence that penis size has an independent, standalone effect – on both attractiveness and the assessment of physical competitiveness.
The results also shed light on the evolutionary function of the unusually large human penis compared to other primates. While in many species penis size is primarily related to sperm competition, the findings suggest that in humans, visual signals for mate choice and male competition may also play a role.
The authors point out that the results are based on perceptual data and do not allow direct conclusions about actual mating behavior or real combat decisions. Furthermore, only static 3D figures were used – dynamic features such as movement or behavior could further modulate the assessment.
The study was funded by several Australian research grants, including funds from the Australian Research Council and the Forrest Research Foundation Fellowship. The data and analysis scripts are publicly available as Supporting Information.
The publication appears at a time when the discussion about physical characteristics and attractiveness is increasingly being conducted from the perspective of evolutionary psychology and social perception. It provides an important experimental contribution to a debate that has so far been predominantly based on surveys and correlation studies.
