Sex difference in travel is concentrated in adolescence and tracks reproductive interests

Abstract

Sexual selection theory suggests that the sex with a higher potential reproductive rate will compete more strongly for access to mates. Stronger intra-sexual competition for mates may explain why males travel more extensively than females in many terrestrial vertebrates. A male-bias in lifetime distance travelled is a purported human universal, although this claim is based primarily on anecdotes. Following sexual maturity, motivation to travel outside the natal territory may vary over the life course for both sexes. Here, we test whether travel behaviour among Tsimane forager-horticulturalists is associated with shifting reproductive priorities across the lifespan. Using structured interviews, we find that sex differences in travel peak during adolescence when men and women are most intensively searching for mates. Among married adults, we find that greater offspring dependency load is associated with reduced travel among women, but not men. Married men are more likely to travel alone than women, but only to the nearest market town and not to other Tsimane villages. We conclude that men's and women's travel behaviour reflects differential gains from mate search and parenting across the life course.

Mobility and Navigation among the Yucatec Maya

“…One hypothesis for the sex difference in range size, particularly in “visiting” or “exploration” ranges (i.e., to other camps, villages or towns), is that men gain fitness benefits through increased mating opportunities. This scale of mobility has not received much attention from anthropologists, but two recent studies of polygynous forager-farmer groups, the Twe and Tsimané, found evidence linking larger male visiting ranges to mating competition, in support of this hypothesis (Miner et al 2014 ; Vashro and Cashdan 2015 ).…”

“…Among Twe forager-farmers in Namibia, spatial ability was associated with yearly visiting range size, and men with larger ranges had more mates (Vashro and Cashdan 2015 ). Among Tsimané farmers in Bolivia, men traveled farther than women only during the mate-seeking years of late adolescence and early adulthood (Miner et al 2014 ).…”

Conflict or congruence? Maternal and infant-centric factors associated with shorter exclusive breastfeeding durations among the Tsimane

“…The population is estimated at 15,000, distributed over 90 villages of varying size (~80-500), ecology (riverine floodplain, terra firme forest), and access to market towns (Miner et al, 2014; Reyes-García et al, 2014). Infant mortality rates vary between 10-20% (Gurven et al, 2007; Gurven, 2012) and the total fertility rate is 9.1 births (McAllister et al, 2012).…”

“…Tsimane mothers carry infants in slings throughout the day and “breastsleep” (McKenna and Gettler, 2016) at night. Mothers are rarely absent from infants; subsistence activities are largely domestic (Gurven et al, 2009) and families generally travel together on longer excursions (Ellis, 1996; Miner et al, 2014). As such, early CF may be motivated by infant-centric factors.…”

Sexual Selection and Life History: Earlier Recalled Puberty Predicts Men’s Phenotypic Masculinization

“…For instance, mental rotation abilities assist with spatial awareness and navigation and thus may have helped ancestral men win mates through enhanced mate location (Miner et al 2014;Gaulin 1992) and targeting of same-sex competitors (Puts 2010) and/or prey items used to obtain mates (Hawkes 1990). Thus, conditions promoting a fast LH strategy including earlier puberty might also promote enhanced spatial cognitive abilities.…”