/sci/ - Science & Math

/sci/ I do not understand the biological reason that human beings cry when alone. I can understand why they would cry when around other people, in order to catch them off guard and try to emotionally manipulate them to various purposes. However I do not understand why humans cry when they believe that they are alone. What purpose does this serve? I am curious as to the scientific reason behind this since I have never in my life cried for any purpose other than emotional manipulation. Is there a biological or evolutionary benefit to crying?
t. fellow human