SexualDimorphism and Mating Patterns of Primate Species
Sexualdimorphism is a situation where the average male differs from theaverage female in that same species. The difference is in terms ofthe body size, weight and other factors affecting the species. Sexualdimorphism involves the use of the logarithm of base ten to theweight obtained from the species.
Thesexual dimorphism can be determined quickly using the values ofdifferent species given for both sexes. The two logarithm value ofweight was subtracted from each other where the logarithm of thefemale was subtracted from that of the male. It has been deduced thatPapio hamadryas has the highest sexual dimorphism than others. It hasa higher sexual dimorphism of 0.29 between the male and the femaleweight. It is obtained by subtracting the logarithm of the value ofthe weight of the male and logarithm of the weight of the female. Itis the species with the higher sexual dimorphism as compared to theothers.
Usually,the value of the logarithm of the weight of male and the female canbe plotted, and analysis is done on the graph. On the graph, thepolygamous was plotted using a positive sign while for the monogamousspecies the plotted using a circle symbol. The male weight was placedon the y-axis while the female weight in logarithm was on the x axis.
Theplotting was then done and the graph analyzed carefully. The line ofreference in the graph is the 450 line that is drawn when the variouspoints of the species were plotted. This line helps to explain as towhy the plotted of the certain species are below the line or abovethe line. The plotted points are above the line when the male weightis higher than the female weight, and it is below when the maleweight is below that of the female. From the graph, the value ofsexual dimorphism is the vertical distance from the line to theplotted point of a given species.
Fromthe graph obtained, it is evident that some of the species plottedpoint was on the 450 line through the graph. Such species are likeLemur mongoz, Galago Allen, Callicebus moloch. In this case, thelogarithm of the weight of both male and female was same thus makingthem present with no sexual dimorphism. For a species to have sexualdimorphism, there should be a difference in the between the male andthe female. In the species, therefore, the male and the female arethe same in terms of body weight and other forms (Rowell& Chism, 1986).
Thereare species whose plotted value was below the 450 line. This speciesis Ateles geoffroyi. This shows that the female is superior to male.Their body weight is higher than that of the male. The sexualdimorphism, in this case, is negative showing that although they havesexual dimorphism, it is where female are superior to male.
Mostof the species fall among the group where the plotting points areabove the 450 line. Apart from those few whose plotting points aredifferent, the remaining species belongs here. In this case, thesexual dimorphism is positive since the weight of the man is higherthan that of the female. It is in this patterning that most speciesdepict including the human being.
Rowell,T., & Chism, J. (1986). Sexualdimorphism and mating systems: Jumping to conclusions page. HumanEvolution, 1(3),215-216.