3. Baker and Bellis (1989) studied the relationship between the percentage of time two human sexual…

3. Baker and Bellis (1989) studied the relationship between the percentage of time two human sexual partners spent together since their last copulation (with each other and the number of sperm produced by males. So, for example they had samples from some couples that had been mostly apart since their last rendezvous and other couples that had spent most of their time together. Data also were corrected for the amount of time since last ejaculation by males. See the results below (you can ignore the distinction between first and subsequent samples; and ignore the graph on the right). (a) Please provide a potential adaptive explanation for these data. (b) Y = 637 – 5.4 X I No. of sperm/ejaculate ( x 106) 200 Eo 60 80 O 20 40 60 80 100 0 20 40 Time together since last copulation (%) Figure 1. Variation in number of sperm in human ejaculates in relation to the percentage of time the male and female have spent together since their last copulation. (a) Copulation; (b) Masturbation. Data points show the estimated number of sperm in a single ejaculate (X + SE based on eight separate counts per ejaculate). O first sample of each type provided by a pair; O: subsequent samples.