Masturbation with ejaculation

Table 1. Multiple regression equations for the number of sperm inseminated during copulation or ejaculated during masturbation. Also shown are the variables entered but subsequently removed from the equations because P>0.05. The equations are based on the total data sets with missing values for independent variables replaced by means as explained in Materials and Methods. Both equations are a very significant fit to the data (P<0.001) and all variables have P<0.05. However, because of pseudo-replication, the regression equations are a tool rather than ends in themselves...

Analysis of the first sample of each type produced by the male of each pair shows that there is a significant heterogeneity in the time to last ejaculation for the different ejaculates (ANOVA F2 144 = 3.33 P = 0.038) with EPCs following more quickly after a recent ejaculate than IPCs and masturbations (EPCs 25 + 6 hrs after the previous ejaculation IPCs 53 7 masturbations 41 3 N = 15, 60 and 72 respectively). Moreover, the recent ejaculation was more likely to be a masturbation (60%, 12/20 before EPC 33%, 116/350 before IPC y2 = 6.031 P = 0.014). 

It is not, however, that the males who contributed EPC ejaculates simply had a higher masturbation rate. Although the sample size for IPCs from these men is small and the heterogeneity not significant (P = 0.24), the men who contributed EPCs show a pattern of abstinence times similar to that by the total contributors (EPCs 22 5 h IPCs 39+12 h Masturbations 46 + 9 h N = 20, 10 and 44 respectively). Moreover, the masturbation rate for EPC contributors (every 46 h) is about the same as for men without partners (every 42 4 h N = 27). Bisexuals, however, maintain a higher rate (every 28 + 7 h N = 5) with an abstinence interval about the same as that which precedes EPCs. 

If this is the explanation, men with large testes and more-symmetrical men would gain a double advantage. Because they seem to manufacture more sperm all together (ejaculating more sperm during both copulation and masturbation), they can inseminate... 

In other woids, Onan s act was not masturbation but coitus interruptus, withdrawal of the penis from the vagina before ejaculation. His crime was not self-abuse or sexual self-satisfaction, but refusal to comply with the law of the Levirate and beget a son with his brother s widow. 

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