Joseph-Marie de Gérando, who penned the ethnographic instructions for the Baudin expedition's voyage to the South Seas (1800–4), advised the French naturalists to investigate among other things ‘the physical strength of the individual savage’ and the ‘senses of the Savage’. He directed them to ‘discover what burdens [the savage] is capable of lifting, carrying or dragging; what are his most successful muscular movements; how quickly he can run; how far he can travel without rest … and so on’. This investigation was evidently inspired by Rousseau's representation of natural man. In his Discourse on the Origin and Foundations of Inequality among Men,Rousseau proposed that there were ‘two kinds of inequality in the human species’: one, a ‘moral or political inequality’ which consisted of the ‘different privileges enjoyed at the expense of others’ which were authorized by the ‘consent of men’, and the second a ‘natural or physical’ inequality ‘established by nature’ through differences in ‘age, health … qualities of mind and soul’ and, most significantly, ‘physical strength’. Rousseau posited that the savage exemplified this natural inequality, for his ‘body is the only instrument he knows’ and ‘necessity obliges him to acquire’ a ‘force and agility’ that civilized man lacks due to his own ‘industry’.
We can conjecture that de Gérando sought verification for Rousseau's hypothesis, urging the explorers to ascertain which senses savage peoples most frequently called upon and what circumstances influenced their development. He even proposed a methodology, which the explorers were rarely if ever in the position to carry out. He suggested that the explorers should judge each particular sense against the following criteria:
1. the art with which two or more sensations are distinguished; 2. the tenuity of sensations that can be noticed; 3. the number of sensations that can be simultaneously grasped; 4. the speed with which the operations are carried out; 5. the capacity to prolong them for a more or less long period without fatigue; 6. finally, the precision of the judgements which sometimes accompany them.