Further selection occurs due to the birth interval for a single female averaging 2–2.5 years. Male fitness would benefit from inseminating other females during a birth interval. This hypothesis is supported by the large scrotal size allowing for increased sperm production.
Further selection is driven by a female's average birth interval of 2–2.5 years. Male fitness would be enhanced by inseminating other females during this period. This hypothesis is supported by the large scrotal size, which facilitates increased sperm production.