hey - i'm so glad you brought this interesting thought, to the table
and i always enjoy the varied responses and comments that can be found here!
this is something i have pondered, at different times in my life.
i have found deep happiness and contentment at times when i was NOT in a significant relationship, or times when my significant relationship (then-marriage) was not functioning in a healthy manner, so it was like being alone.
i've discovered that i can find contentment and satisfaction in many different ways. but there is a common thread - a connectedness to other human beings. whether that has been my children, friends, people i met doing volunteer work (both fellow volunteers and people that were being helped) and friendships that were founded on an online forum (this forum and one other)
humans are genetically designed to be social. part of this is for procreative purposes, so it is hardwired into our DNA. however, it does not have to be a romantic/sexual connection to provide deep comfort, joy and satisfaction. but i believe we all have an inner need to feel connected to other humans.
thanks again for the interesting post