– by Eric Schniter, Michael Gurven, & Hillard Kaplan

Humans depend on culturally transmitted knowledge and skills crucial for their survival. But how is essential culture transmitted?

In economically modern human societies, most youngsters are formally educated alongside their similar-aged peers by unrelated teachers from an older generation. Adults in modern societies often develop into specialists, learning novel specialized skills from their coworkers and prestigious peers. But is this pattern of “horizontal” and “oblique” transmission from unrelated others the most fundamental mode of human culture transmission?

Evidence from subsistence groups like the Tsimane suggest that the patterns of cultural transmission, schooling, and skill development seen in economically modern society are not universal to all humans and were likely uncommon among our ancestors who relied on multi-generational broad social structures of kin-based exchange.

In our recent study in Evolution & Human Behavior, we brought a life history approach to the study of transmission vectors that considers how changes in embodied capital, combined with gender and relatedness, affect the costs and benefits to both the influencer and the learner. We emphasize the investments made in knowledge and skill across the human lifespan, and the returns on these investments at different ages that manifest in the array of competencies we see in a cross-section of society. We adapt the vector framework introduced by Luigi Cavalli-Sforza and Marcus Feldman to describe vertical, oblique, and horizontal cultural transmission relationships (see Figure 1).

Figure 1. Schematic representation of the intra- and inter-generational cultural transmission vectors, both related and unrelated that potentially influence receivers’ culture acquisition. Our cultural transmission study focuses on the relationships in bold fonts and colors.

So, what did we find? When do people learn, from whom, and how?

Our study focusing on 421 adult Tsimane forager-farmers native to Bolivia sheds light on how essential skills and specific domains of knowledge find their way from person to person and from one generation to the next. We examined the transmission vectors and styles of influence behind Tsimane people’s acquisition of 92 skills, ranging from those involving foraging, domestic chores, crafts and tool manufacture, childcare, music, and more. This transitioning community, living at the intersection of traditional foraging and farming practices and the rapidly changing demands of market integration, provides a unique lens to understand the vectors and influences driving cultural transmission.

We used a survey approach to gather knowledge about the skills that people had, their proficiency with those skills, and their reports of who influenced their skill acquisition by teaching, correction, helpful example, encouragement, or discouragement. Tsimane people report acquiring basic competency with most skills by the end of childhood and developing their skill proficiency further throughout adulthood.

Older, same-sex relatives predominantly influence Tsimane culture transmission, and in a variety of ways. They lead by example, directly instruct, correct learner’s mistakes, and sometimes just encourage and positively reinforce behaviors. Older adults are named most for these influences, despite the greater amount of time that kids spend interacting with same-generation peers while developing proficiency with most skills.

95% of culture transmission is reported as coming from within families (87% blood relatives, 8% related by marriage) and 75% from older kin. Vertical transmission from parents is most common, followed by oblique transmission from older kin. For example, grandparents –revered for their wisdom and experience—play a crucial role in imparting difficult-to-acquire skills that demand less physical strength but more complex knowledge, such as music performance, storytelling, and crafting. In contrast, peers of the same generation tend to positively influence the acquisition of modern, market-oriented skills, like finding wage labor opportunities and using machines for farming.

While similar-aged peers facilitate the acquisition of modern skills, they are reported to be the least helpful when it comes to positively influencing traditional skill acquisition. Unlike older kin, peers of the same generation are more likely to be competitors during the skill acquisition process, explaining why they are reported to be the mostly likely contributors of discouragement, a negative influence intended to inhibit skill acquisition.

We examined a diverse set of essential Tsimane skills and types of knowledge that has been conserved for untold generations, underscoring the important role of older adults and the multi-generational support of youngsters and young adults. This dominant pattern of kin-biased cultural transmission from older to younger generations mirrors the Tsimane pattern of kin-biased net food transfers between generations and within extended families (see here and here).

In subsistence societies, essential skills continue to develop for decades after they have been acquired (e.g., see here), forming older adults into “banks” of accumulated cultural solutions and practical knowledge (e.g., see here, and here). Our findings are consistent with the view that older-to-younger cultural transmission is the result of selection for a long lifespan favoring peak abilities for information retrieval and transmission to younger kin at late ages.

Generations of cultural isolation likely helped the Tsimane conserve their multigenerational system of cooperation and downward traditional culture transmission. However with rapid modernization, the current and future generations will face new challenges. Older adults’ contributions to their forager-farmer economy have been possible because of their comparative advantages and accumulated experience that comes with age. As transitioning societies increasingly value novel skillsets, and as younger generations develop comparatively greater proficiency and productivity with these modern skills, the opportunities for positive cultural influence and transfers from younger to older generations will grow. These results suggest that successful aging among adults, in both Tsimane and economically modern societies, will hinge on both upward inter-generational flows of knowledge and resources, and younger generations maintaining an appreciation for older adults’ roles as trusty helpers, educators, and experts of cultural traditions.

Read the original paper: Schniter, E., Kaplan, H. S., & Gurven, M. (2023). Cultural transmission vectors of essential knowledge and skills among Tsimane forager-farmers. Evolution and Human Behavior.