In the name of Allah, Most Gracious, and Most Merciful
No one can give an answer to this question!
Even if the reason behind life is quite evident, no one can notice the Maker of this, and how he did for!
Also, it's evident to know how the creation of humans in the womb happens:
In most cases it happens when the semen fertilizes the ovum!
But, what is surely out of man's will is: