Philosophical Transactions of the Royal Society B: Biological Sciences
Cooperation in food acquisition is a hallmark of the human species. Given that costs and benefits... more Cooperation in food acquisition is a hallmark of the human species. Given that costs and benefits of cooperation vary among production regimes and work activities, the transition from hunting-and-gathering to agriculture is likely to have reshaped the structure of cooperative subsistence networks. Hunter–gatherers often forage in groups and are generally more interdependent and experience higher short-term food acquisition risk than horticulturalists, suggesting that cooperative labour should be more widespread and frequent for hunter–gatherers. Here we compare female cooperative labour networks of Batek hunter–gatherers of Peninsular Malaysia and Tsimane forager–horticulturalists of Bolivia. We find that Batek foraging results in high daily variation in labour partnerships, facilitating frequent cooperation in diffuse networks comprised of kin and non-kin. By contrast, Tsimane horticulture involves more restricted giving and receiving of labour, confined mostly to spouses and prima...
Evidence from the ethnographic and archaeological records reveals that humans often rely on out-g... more Evidence from the ethnographic and archaeological records reveals that humans often rely on out-group relationships for access to non-local resources and resource buffering. However, little is known about how actors choose out-group cooperative partners. The existing literature suggests that (in-group) partner choice is based on characteristics associated with greater cooperation (e.g., trustworthiness and productivity). Is out-group partner choice based on the same criteria as in-group? Because out-groups may be unique sources of resource access, we suggest that out-group partner choice should track characteristics of both the candidate partner and the partner's group that are associated with benefits for the actor. To assess partner choice, we employed a non-anonymous, one-shot economic game where participants could allocate money towards in-group and out-group strangers. Participants were from three populations of Bolivian horticulturalists (n = 200) that range in their market integration and their mobility, thus capturing variation in potential benefits to out-group cooperation. We find that individual-level qualities of prospective partners, such as wealth and trustworthiness, affect allocation behavior differently for in-group vs out-group prospective partners. While we find no consistent effects of perceived group qualities on a donor's giving to in-group and out-group members, the relevance of out-group market resource access for Tsimane' donors' allocations suggests that, at least when it comes to dividing a limited resource, qualities associated with a group can affect partner preference. Taken together, results provide insight into patterns of intergroup relationship building that have been crucial in the human lineage.
ABSTRACT: Objectives: This study explores whether cardiovascular fitness levels and senescent dec... more ABSTRACT: Objectives: This study explores whether cardiovascular fitness levels and senescent decline are similar
in the Tsimane of Bolivia and Canadians, as well as other subsistence and industrialized populations. Among Tsimane,
we examine whether morbidity predicts lower levels and faster decline of cardiovascular fitness, or whether
their lifestyle (e.g., high physical activity) promotes high levels and slow decline. Alternatively, high activity levels and
morbidity might counterbalance such that Tsimane fitness levels and decline are similar to those in industrialized
populations.
Methods: Maximal oxygen uptake (VO2max) was estimated using a step test heart rate method for 701 participants.
We compared these estimates to the Canadian Health Measures Survey and previous studies in industrialized and subsistence
populations. We evaluated whether health indicators and proxies for market integration were associated with
VO2max levels and rate of decline for the Tsimane.
Results: The Tsimane have significantly higher levels of VO2max and slower rates of decline than Canadians; initial
evidence suggests differences in VO2max levels between other subsistence and industrialized populations. Low hemoglobin
predicts low VO2max for Tsimane women while helminth infection predicts high VO2max for Tsimane men,
though results might be specific to the VO2max scaling parameter used. No variables tested interact with age to moderate
decline.
Conclusions: The Tsimane demonstrate higher levels of cardiovascular fitness than industrialized populations, but
levels similar to other subsistence populations. The high VO2max of Tsimane is consistent with their high physical
activity and few indicators of cardiovascular disease, measured in previous studies. Am. J. Hum. Biol. 25:756–769,
2013
Sedentary lifestyle contributes to osteoporosis and fragility fracture risks among modern humans,... more Sedentary lifestyle contributes to osteoporosis and fragility fracture risks among modern humans, but whether such risks are prevalent in physically active pre-industrial societies with lower life expectancies is unclear. Osteoporosis should be readily observable in pre-industrial societies if it was regularly experienced over human history. In this study of 142 older adult Tsimane forager-horticulturalists (mean age ± SD = 62.1 ± 8.6, range = 50-85, 51% female) we use calcaneal quantitative ultrasonography (qUS) to assess bone status, document prevalence of adults with reduced bone status, and identify factors (demographic, anthropometric, immunological, kinesthetic) associated with reduced bone status. Men (23%) are as likely as women (25%) to have reduced bone status, although age-related decline in qUS parameters is attenuated for men. Adiposity and fat-free mass positively co-vary with qUS parameters for women but not men. Leukocyte count is inversely associated with qUS parameters controlling for potential confounders; leukocyte count is positively correlated within adults over time, and adults with persistently low counts have higher adjusted qUS parameters (6-8%) than adults with a high count. Reduced bone status characteristic of osteoporosis is common among active Tsimane with minimal exposure to osteoporosis risk factors found in industrialized societies, but with energetic constraints and high pathogen burden. This article is protected by copyright. All rights reserved.
Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 5, 2015
While many hormones play vital roles in facilitating or reinforcing cooperative behaviour, the ne... more While many hormones play vital roles in facilitating or reinforcing cooperative behaviour, the neurohormones underlying competitive and cooperative behaviours are largely conserved across all mammals. This raises the question of how endocrine mechanisms have been shaped by selection to produce different levels of cooperation in different species. Multiple components of endocrine physiology-from baseline hormone concentrations, to binding proteins, to the receptor sensitivity and specificity-can evolve independently and be impacted by current socio-ecological conditions or individual status, thus potentially generating a wide range of variation within and between species. Here, we highlight several neurohormones and variation in hormone receptor genes associated with cooperation, focusing on the role of oxytocin and testosterone in contexts ranging from parenting and pair-bonding to reciprocity and territorial defence. While the studies reviewed herein describe the current state of t...
Sharing and exchange are common practices for minimizing food insecurity in rural populations. Th... more Sharing and exchange are common practices for minimizing food insecurity in rural populations. The advent of markets and monetization in egalitarian indigenous populations presents an alternative means of managing risk, with the potential impact of eroding traditional networks. We test whether market involvement buffers several types of risk and reduces traditional sharing behavior among Tsimane Amerindians of the Bolivian Amazon. Results vary based on type of market integration and scale of analysis (household vs. village), consistent with the notion that local culture and ecology shape risk management strategies. Greater wealth and income were unassociated with the reliance on others for food, or on reciprocity, but wealth was associated with a greater proportion of food given to others (i.e., giving intensity) and a greater number of sharing partners (i.e., sharing breadth). Across villages, greater mean income was negatively associated with reciprocity, but economic inequality was positively associated with giving intensity and sharing breadth. Incipient market integration does not necessarily replace traditional buffering strategies but instead can often enhance social capital.
How did humans sleep before the modern era? Because the tools to measure sleep under natural cond... more How did humans sleep before the modern era? Because the tools to measure sleep under natural conditions were developed long after the invention of the electric devices suspected of delaying and reducing sleep, we investigated sleep in three preindustrial societies [1-3]. We find that all three show similar sleep organization, suggesting that they express core human sleep patterns, most likely characteristic of pre-modern era Homo sapiens. Sleep periods, the times from onset to offset, averaged 6.9-8.5 hr, with sleep durations of 5.7-7.1 hr, amounts near the low end of those industrial societies [4-7]. There was a difference of nearly 1 hr between summer and winter sleep. Daily variation in sleep duration was strongly linked to time of onset, rather than offset. None of these groups began sleep near sunset, onset occurring, on average, 3.3 hr after sunset. Awakening was usually before sunrise. The sleep period consistently occurred during the nighttime period of falling environmental...
Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 5, 2015
In foraging and other productive activities, individuals make choices regarding whether and with ... more In foraging and other productive activities, individuals make choices regarding whether and with whom to cooperate, and in what capacities. The size and composition of cooperative groups can be understood as a self-organized outcome of these choices, which are made under local ecological and social constraints. This article describes a theoretical framework for explaining the size and composition of foraging groups based on three principles: (i) the sexual division of labour; (ii) the intergenerational division of labour; and (iii) economies of scale in production. We test predictions from the theory with data from two field contexts: Tsimane' game hunters of lowland Bolivia, and Jenu Kuruba honey collectors of South India. In each case, we estimate the impacts of group size and individual group members' effort on group success. We characterize differences in the skill requirements of different foraging activities and show that individuals participate more frequently in acti...
Coall & Hertwig (C&H) bring attention to alternative accounts of grandparental investment from ec... more Coall & Hertwig (C&H) bring attention to alternative accounts of grandparental investment from economics, evolutionary anthropology, psychology, and sociology, which have yet to be reconciled. We attempt to help integrate some of the disparate perspectives by expanding the scope of the evolutionary perspective, highlighting some gaps, and discussing problems with the authors' treatment of grandparents in traditional societies.
New research into variation in mutation rates across nucleotide positions in human mitochondrial ... more New research into variation in mutation rates across nucleotide positions in human mitochondrial DNA (mtDNA) calls into question population genetics models that assume a constant mutation rate for all sites in a sequence, particularly for hypervariable control region segments I and II. Related to this research is discovering the extent to which highly polymorphic sites are really mutational "hot spots" rather than "old" sites rooted early in the phylogenetic tree. This issue is addressed through the analysis of linkage disequilibrium patterns in the mtDNAs of 10 human populations. Hot spots can be expected to show little or no disequilibrium since they can be interpreted as having randomly expressed patterns. In fact, the results suggest that many highly polymorphic sites are not old sites, but instead are hot spots. Suspected hot spots are listed and compared with hypervariable sites given by Wakeley (1993) and Hasegawa et al. (1993).
Philosophical Transactions of the Royal Society B: Biological Sciences
Cooperation in food acquisition is a hallmark of the human species. Given that costs and benefits... more Cooperation in food acquisition is a hallmark of the human species. Given that costs and benefits of cooperation vary among production regimes and work activities, the transition from hunting-and-gathering to agriculture is likely to have reshaped the structure of cooperative subsistence networks. Hunter–gatherers often forage in groups and are generally more interdependent and experience higher short-term food acquisition risk than horticulturalists, suggesting that cooperative labour should be more widespread and frequent for hunter–gatherers. Here we compare female cooperative labour networks of Batek hunter–gatherers of Peninsular Malaysia and Tsimane forager–horticulturalists of Bolivia. We find that Batek foraging results in high daily variation in labour partnerships, facilitating frequent cooperation in diffuse networks comprised of kin and non-kin. By contrast, Tsimane horticulture involves more restricted giving and receiving of labour, confined mostly to spouses and prima...
Evidence from the ethnographic and archaeological records reveals that humans often rely on out-g... more Evidence from the ethnographic and archaeological records reveals that humans often rely on out-group relationships for access to non-local resources and resource buffering. However, little is known about how actors choose out-group cooperative partners. The existing literature suggests that (in-group) partner choice is based on characteristics associated with greater cooperation (e.g., trustworthiness and productivity). Is out-group partner choice based on the same criteria as in-group? Because out-groups may be unique sources of resource access, we suggest that out-group partner choice should track characteristics of both the candidate partner and the partner's group that are associated with benefits for the actor. To assess partner choice, we employed a non-anonymous, one-shot economic game where participants could allocate money towards in-group and out-group strangers. Participants were from three populations of Bolivian horticulturalists (n = 200) that range in their market integration and their mobility, thus capturing variation in potential benefits to out-group cooperation. We find that individual-level qualities of prospective partners, such as wealth and trustworthiness, affect allocation behavior differently for in-group vs out-group prospective partners. While we find no consistent effects of perceived group qualities on a donor's giving to in-group and out-group members, the relevance of out-group market resource access for Tsimane' donors' allocations suggests that, at least when it comes to dividing a limited resource, qualities associated with a group can affect partner preference. Taken together, results provide insight into patterns of intergroup relationship building that have been crucial in the human lineage.
ABSTRACT: Objectives: This study explores whether cardiovascular fitness levels and senescent dec... more ABSTRACT: Objectives: This study explores whether cardiovascular fitness levels and senescent decline are similar
in the Tsimane of Bolivia and Canadians, as well as other subsistence and industrialized populations. Among Tsimane,
we examine whether morbidity predicts lower levels and faster decline of cardiovascular fitness, or whether
their lifestyle (e.g., high physical activity) promotes high levels and slow decline. Alternatively, high activity levels and
morbidity might counterbalance such that Tsimane fitness levels and decline are similar to those in industrialized
populations.
Methods: Maximal oxygen uptake (VO2max) was estimated using a step test heart rate method for 701 participants.
We compared these estimates to the Canadian Health Measures Survey and previous studies in industrialized and subsistence
populations. We evaluated whether health indicators and proxies for market integration were associated with
VO2max levels and rate of decline for the Tsimane.
Results: The Tsimane have significantly higher levels of VO2max and slower rates of decline than Canadians; initial
evidence suggests differences in VO2max levels between other subsistence and industrialized populations. Low hemoglobin
predicts low VO2max for Tsimane women while helminth infection predicts high VO2max for Tsimane men,
though results might be specific to the VO2max scaling parameter used. No variables tested interact with age to moderate
decline.
Conclusions: The Tsimane demonstrate higher levels of cardiovascular fitness than industrialized populations, but
levels similar to other subsistence populations. The high VO2max of Tsimane is consistent with their high physical
activity and few indicators of cardiovascular disease, measured in previous studies. Am. J. Hum. Biol. 25:756–769,
2013
Sedentary lifestyle contributes to osteoporosis and fragility fracture risks among modern humans,... more Sedentary lifestyle contributes to osteoporosis and fragility fracture risks among modern humans, but whether such risks are prevalent in physically active pre-industrial societies with lower life expectancies is unclear. Osteoporosis should be readily observable in pre-industrial societies if it was regularly experienced over human history. In this study of 142 older adult Tsimane forager-horticulturalists (mean age ± SD = 62.1 ± 8.6, range = 50-85, 51% female) we use calcaneal quantitative ultrasonography (qUS) to assess bone status, document prevalence of adults with reduced bone status, and identify factors (demographic, anthropometric, immunological, kinesthetic) associated with reduced bone status. Men (23%) are as likely as women (25%) to have reduced bone status, although age-related decline in qUS parameters is attenuated for men. Adiposity and fat-free mass positively co-vary with qUS parameters for women but not men. Leukocyte count is inversely associated with qUS parameters controlling for potential confounders; leukocyte count is positively correlated within adults over time, and adults with persistently low counts have higher adjusted qUS parameters (6-8%) than adults with a high count. Reduced bone status characteristic of osteoporosis is common among active Tsimane with minimal exposure to osteoporosis risk factors found in industrialized societies, but with energetic constraints and high pathogen burden. This article is protected by copyright. All rights reserved.
Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 5, 2015
While many hormones play vital roles in facilitating or reinforcing cooperative behaviour, the ne... more While many hormones play vital roles in facilitating or reinforcing cooperative behaviour, the neurohormones underlying competitive and cooperative behaviours are largely conserved across all mammals. This raises the question of how endocrine mechanisms have been shaped by selection to produce different levels of cooperation in different species. Multiple components of endocrine physiology-from baseline hormone concentrations, to binding proteins, to the receptor sensitivity and specificity-can evolve independently and be impacted by current socio-ecological conditions or individual status, thus potentially generating a wide range of variation within and between species. Here, we highlight several neurohormones and variation in hormone receptor genes associated with cooperation, focusing on the role of oxytocin and testosterone in contexts ranging from parenting and pair-bonding to reciprocity and territorial defence. While the studies reviewed herein describe the current state of t...
Sharing and exchange are common practices for minimizing food insecurity in rural populations. Th... more Sharing and exchange are common practices for minimizing food insecurity in rural populations. The advent of markets and monetization in egalitarian indigenous populations presents an alternative means of managing risk, with the potential impact of eroding traditional networks. We test whether market involvement buffers several types of risk and reduces traditional sharing behavior among Tsimane Amerindians of the Bolivian Amazon. Results vary based on type of market integration and scale of analysis (household vs. village), consistent with the notion that local culture and ecology shape risk management strategies. Greater wealth and income were unassociated with the reliance on others for food, or on reciprocity, but wealth was associated with a greater proportion of food given to others (i.e., giving intensity) and a greater number of sharing partners (i.e., sharing breadth). Across villages, greater mean income was negatively associated with reciprocity, but economic inequality was positively associated with giving intensity and sharing breadth. Incipient market integration does not necessarily replace traditional buffering strategies but instead can often enhance social capital.
How did humans sleep before the modern era? Because the tools to measure sleep under natural cond... more How did humans sleep before the modern era? Because the tools to measure sleep under natural conditions were developed long after the invention of the electric devices suspected of delaying and reducing sleep, we investigated sleep in three preindustrial societies [1-3]. We find that all three show similar sleep organization, suggesting that they express core human sleep patterns, most likely characteristic of pre-modern era Homo sapiens. Sleep periods, the times from onset to offset, averaged 6.9-8.5 hr, with sleep durations of 5.7-7.1 hr, amounts near the low end of those industrial societies [4-7]. There was a difference of nearly 1 hr between summer and winter sleep. Daily variation in sleep duration was strongly linked to time of onset, rather than offset. None of these groups began sleep near sunset, onset occurring, on average, 3.3 hr after sunset. Awakening was usually before sunrise. The sleep period consistently occurred during the nighttime period of falling environmental...
Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 5, 2015
In foraging and other productive activities, individuals make choices regarding whether and with ... more In foraging and other productive activities, individuals make choices regarding whether and with whom to cooperate, and in what capacities. The size and composition of cooperative groups can be understood as a self-organized outcome of these choices, which are made under local ecological and social constraints. This article describes a theoretical framework for explaining the size and composition of foraging groups based on three principles: (i) the sexual division of labour; (ii) the intergenerational division of labour; and (iii) economies of scale in production. We test predictions from the theory with data from two field contexts: Tsimane' game hunters of lowland Bolivia, and Jenu Kuruba honey collectors of South India. In each case, we estimate the impacts of group size and individual group members' effort on group success. We characterize differences in the skill requirements of different foraging activities and show that individuals participate more frequently in acti...
Coall & Hertwig (C&H) bring attention to alternative accounts of grandparental investment from ec... more Coall & Hertwig (C&H) bring attention to alternative accounts of grandparental investment from economics, evolutionary anthropology, psychology, and sociology, which have yet to be reconciled. We attempt to help integrate some of the disparate perspectives by expanding the scope of the evolutionary perspective, highlighting some gaps, and discussing problems with the authors' treatment of grandparents in traditional societies.
New research into variation in mutation rates across nucleotide positions in human mitochondrial ... more New research into variation in mutation rates across nucleotide positions in human mitochondrial DNA (mtDNA) calls into question population genetics models that assume a constant mutation rate for all sites in a sequence, particularly for hypervariable control region segments I and II. Related to this research is discovering the extent to which highly polymorphic sites are really mutational "hot spots" rather than "old" sites rooted early in the phylogenetic tree. This issue is addressed through the analysis of linkage disequilibrium patterns in the mtDNAs of 10 human populations. Hot spots can be expected to show little or no disequilibrium since they can be interpreted as having randomly expressed patterns. In fact, the results suggest that many highly polymorphic sites are not old sites, but instead are hot spots. Suspected hot spots are listed and compared with hypervariable sites given by Wakeley (1993) and Hasegawa et al. (1993).
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Papers by Michael Gurven
in the Tsimane of Bolivia and Canadians, as well as other subsistence and industrialized populations. Among Tsimane,
we examine whether morbidity predicts lower levels and faster decline of cardiovascular fitness, or whether
their lifestyle (e.g., high physical activity) promotes high levels and slow decline. Alternatively, high activity levels and
morbidity might counterbalance such that Tsimane fitness levels and decline are similar to those in industrialized
populations.
Methods: Maximal oxygen uptake (VO2max) was estimated using a step test heart rate method for 701 participants.
We compared these estimates to the Canadian Health Measures Survey and previous studies in industrialized and subsistence
populations. We evaluated whether health indicators and proxies for market integration were associated with
VO2max levels and rate of decline for the Tsimane.
Results: The Tsimane have significantly higher levels of VO2max and slower rates of decline than Canadians; initial
evidence suggests differences in VO2max levels between other subsistence and industrialized populations. Low hemoglobin
predicts low VO2max for Tsimane women while helminth infection predicts high VO2max for Tsimane men,
though results might be specific to the VO2max scaling parameter used. No variables tested interact with age to moderate
decline.
Conclusions: The Tsimane demonstrate higher levels of cardiovascular fitness than industrialized populations, but
levels similar to other subsistence populations. The high VO2max of Tsimane is consistent with their high physical
activity and few indicators of cardiovascular disease, measured in previous studies. Am. J. Hum. Biol. 25:756–769,
2013
of food given to others (i.e., giving intensity) and a greater number of sharing partners (i.e., sharing breadth). Across villages, greater mean income was negatively associated with
reciprocity, but economic inequality was positively associated
with giving intensity and sharing breadth. Incipient market
integration does not necessarily replace traditional buffering
strategies but instead can often enhance social capital.
in the Tsimane of Bolivia and Canadians, as well as other subsistence and industrialized populations. Among Tsimane,
we examine whether morbidity predicts lower levels and faster decline of cardiovascular fitness, or whether
their lifestyle (e.g., high physical activity) promotes high levels and slow decline. Alternatively, high activity levels and
morbidity might counterbalance such that Tsimane fitness levels and decline are similar to those in industrialized
populations.
Methods: Maximal oxygen uptake (VO2max) was estimated using a step test heart rate method for 701 participants.
We compared these estimates to the Canadian Health Measures Survey and previous studies in industrialized and subsistence
populations. We evaluated whether health indicators and proxies for market integration were associated with
VO2max levels and rate of decline for the Tsimane.
Results: The Tsimane have significantly higher levels of VO2max and slower rates of decline than Canadians; initial
evidence suggests differences in VO2max levels between other subsistence and industrialized populations. Low hemoglobin
predicts low VO2max for Tsimane women while helminth infection predicts high VO2max for Tsimane men,
though results might be specific to the VO2max scaling parameter used. No variables tested interact with age to moderate
decline.
Conclusions: The Tsimane demonstrate higher levels of cardiovascular fitness than industrialized populations, but
levels similar to other subsistence populations. The high VO2max of Tsimane is consistent with their high physical
activity and few indicators of cardiovascular disease, measured in previous studies. Am. J. Hum. Biol. 25:756–769,
2013
of food given to others (i.e., giving intensity) and a greater number of sharing partners (i.e., sharing breadth). Across villages, greater mean income was negatively associated with
reciprocity, but economic inequality was positively associated
with giving intensity and sharing breadth. Incipient market
integration does not necessarily replace traditional buffering
strategies but instead can often enhance social capital.