Do we as humans need love to survive?Kind of, yeah.
There was a whole series of studies done in the 1950's with baby monkeys (Harry Harlow, Monkey Love Experiments), where they showed that raising a baby without it's mother, and with no source of affection was devastating to them. It caused permanent damage, and, in some cases, caused them to just break down and die. Note that these monkeys were well fed, cleaned, kept in a temperature-controlled environment, provided with all the necessities of life, but no nurturing affection or love. It destroyed them.
As for human studies, experimentation in naturally impossible, but there were studies done in cases where huge numbers of children were committed to government-run orphanages. The orphanages had employees to make sure the children were feed, cleaned and clothed, but they had neither the time nor the resposibility to give the children expressions of love. Those children almost universally suffered very serious psychological effects throughout their lives, and, in some cases, literally died of neglect.
Now, these are all studies of children that are still developing, but the evidence is clear that there's a basic human need for some kind of love and attachment. As we become older and more psychologically self-sufficient, we're less sensitive to such things, and can survive without any kind of love in our lives, but we're still humans and we still need human connections. It's more that a good thing to have, such is critical need in our lives.
I've read about the orphanage study, but what about adults? What happens when you pass the age where your physical survival depends solely on yourself?
I say you don't need human love (by which I mean romantic love). It's a good thing to have if you can get it, but some people can't. You have no control over whether anyone loves you.
The only unconditional love you can ever have is that of a cat or a dog, perhaps another fur-bearing mammal like a fennec fox. Feed them, play with them, and pet them and they will love you forever. They don't use people or betray them.
As long as you have good friends and loving pets you can be satisfied with life.
Yes. It's primarily feelings of love that prompt parents to care for their children. Human children have not evolved to be self-sufficient, so if their parents abandoned them, they would not survive. And if human children didn't survive, the species would die out.