The longer and thicker a man's penis the more effective he can be at eliminating sperm from another man because if a woman has more than one male sexual partner over 48 hours, then the sperm of these men compete for reproductive access to her egg.
The Role of Length & Width-
The Importance of the Refractory Period-
After men ejaculate, they experience a refractory period which means that they will lose their erection to half its full erect size within on minute of ejaculating. Their penises also become hypersensitive which will make further stimulation to the penis feel unpleasant. Men typically stay in the refractory period between 30 minutes to 24 hours and are rendered temporarily impotent following ejaculation. The reason this occurs is o prevent removal of a man's own sperm from his partner's vagina.
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