Student assignment. (requirement for course by Peter Kabai)

Females drive primate social evolution.

Grace Hinton, Wildlife management elective course

In the study Females drive primate social evolution written by Patrik Lindenfors, Laila Fröberg and Charles L. Nunn the first hypothesis was that male group size lags behind female group size in primate groups. The second hypothesis in this study questioned what factors that affect the numbers of adult males and females within groups. Though formerly studies in this matter have been focusing on the ecological variables, this study wanted to test the female driven social evolution.

The authors imply that when investigating patterns across species, at least three factors may cause the number of males (male group size) to lag behind the number of females (female group size). First, changes in the number of males may be sensitive to female sexual behaviour, such as oestrous synchrony, which may not evolve instantaneously as female group size increases. Selection for such adjustments in female sexual behaviour may result from variation in the degree of predation or infanticide risk (van Schaik & Hörstermann 1994; van Schaik & Janson 2000). Second, individuals may require time to evolve defences to infectious disease risk that are expected to increase in multimalemultifemale groups, including risks of acquiring socially or sexually transmitted diseases (Freeland 1976; Møller et al. 1993; Nunn et al.2000; Nunn & Altizer 2004). Finally, cognitive constraints may limit the number of individuals in groups (Dunbar 1988). For example, male alliances in multimale primate groups require a degree of cooperation that is unlikely to exist in strictly polygynous systems (Sommer 1988).

Studies that have been completed concerning primates general framework show that it is a female-driven social evolution.

Datas that was needed for testing the hypotheses that male group size lags behind female group in a primate group where collected and group sizes was log-transformed. To present suitable result, full dataset and dataset with solitary species removed was used. The statistical result of the relationship between male group size and female group size in primates was represented in a plot diagram.

Comparing the diagrams, the result from the plot diagrams show that group sizes of male and females where significantly correlated; this even so when both using the full dataset and when solitary species was excluded, seen in diagram (b). This backs up the results from previously studies.

The different group-types that were studied have to be mentioned when looking at the differences in the result. The group types that was studied was; unimale- multifemale, multifemale- multifemale and unifemale- multimale. A unimale-multifemale group would be expected to have a negative result in the plot diagram whereas unifemale- multimale group would be expected to show a positive result.

Even though this study and previously studies can correlate male-female groups size still it must be concerned other alternatives. One question is the ecological factors that limit the reproductive success. We know that female fitness is more closely related to access to food, so therefore food competition will more strongly affect female social relationships than male social relationships. In controversy social relationships among males will be mostly affected by the degree of competition for mates.

Though this study shows correlation between female and male, still a great variation of data is seen. The variation is not only seen across different species but also between different groups in the same species. A reason for this can be that excess to food and competition for the resources given is not only between individuals in the group but also among different groups and species.

All these questions point that future studies should take in concern the ecological factors influencing on the group. Studies should also put more focus on the female as these studies show that they are the drive in the primate society.

http://www.leeds.ac.uk/chb/lectures/anthl_11.html

http://en.wikipedia.org/wiki/Primate

http://www.nationalgeografic.com

http://members.tripod.com/uakari/definitions.html#L

http://www.federation.g3z.com/FedSeries/FallOfMankind/Primates.htm

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Females drive primate social evolution. Grace Hinton, Wildlife management elective course In the study Females drive primate social evolution written by Patrik Lindenfors, Laila Fröberg and Charles L. Nunn the first hypothesis was that male group size lags behind female group size in primate groups. The second hypothesis in this study questioned what factors that affect the numbers of adult males and females within groups. Though formerly studies in this matter have been focusing on the ecological variables, this study wanted to test the female driven social evolution. The authors imply that when investigating patterns across species, at least three factors may cause the number of males (male group size) to lag behind the number of females (female group size). First, changes in the number of males may be sensitive to female sexual behaviour, such as oestrous synchrony, which may not evolve instantaneously as female group size increases. Selection for such adjustments in female sexual behaviour may result from variation in the degree of predation or infanticide risk (van Schaik & Hörstermann 1994; van Schaik & Janson 2000). Second, individuals may require time to evolve defences to infectious disease risk that are expected to increase in multimalemultifemale groups, including risks of acquiring socially or sexually transmitted diseases (Freeland 1976; Møller et al. 1993; Nunn et al.2000; Nunn & Altizer 2004). Finally, cognitive constraints may limit the number of individuals in groups (Dunbar 1988). For example, male alliances in multimale primate groups require a degree of cooperation that is unlikely to exist in strictly polygynous systems (Sommer 1988). Studies that have been completed concerning primates general framework show that it is a female-driven social evolution. Datas that was needed for testing the hypotheses that male group size lags behind female group in a primate group where collected and group sizes was log-transformed. To present suitable result, full dataset and dataset with solitary species removed was used. The statistical result of the relationship between male group size and female group size in primates was represented in a plot diagram. Comparing the diagrams, the result from the plot diagrams show that group sizes of male and females where significantly correlated; this even so when both using the full dataset and when solitary species was excluded, seen in diagram (b). This backs up the results from previously studies. The different group-types that were studied have to be mentioned when looking at the differences in the result. The group types that was studied was; unimale- multifemale, multifemale- multifemale and unifemale- multimale. A unimale-multifemale group would be expected to have a negative result in the plot diagram whereas unifemale- multimale group would be expected to show a positive result. Even though this study and previously studies can correlate male-female groups size still it must be concerned other alternatives. One question is the ecological factors that limit the reproductive success. We know that female fitness is more closely related to access to food, so therefore food competition will more strongly affect female social relationships than male social relationships. In controversy social relationships among males will be mostly affected by the degree of competition for mates. Though this study shows correlation between female and male, still a great variation of data is seen. The variation is not only seen across different species but also between different groups in the same species. A reason for this can be that excess to food and competition for the resources given is not only between individuals in the group but also among different groups and species. All these questions point that future studies should take in concern the ecological factors influencing on the group. Studies should also put more focus on the female as these studies show that they are the drive in the primate society. http://www.leeds.ac.uk/chb/lectures/anthl_11.html http://en.wikipedia.org/wiki/Primate http://www.nationalgeografic.com http://members.tripod.com/uakari/definitions.html#L http://www.federation.g3z.com/FedSeries/FallOfMankind/Primates.htm

Notes (if any) by Peter Kabai: