From what I've read both about Cro-Magnon people and research on modern social problems, we miss small group interactions. We are overwhelmed with simply too big masses of people. We are "programmed" to feel good in max 100 persons groups, to feel good.
I remember the research on Bonobo apes, which was seen as very similar to human issues, that when their living space was overcrowded their social interactions suffered - violence, abandoning the young and various other unhealthy behaviors were noticed.
We live in overcrowded towns and cities, bombarded each day with information about more people, we have hundreds of "friends" online, trying to remember and know them all, we are proud to have big friend groups and interact with thousands of people over the years.
It is seen as one of the sources of anxiety, depression and social phobias. We do best in small groups, where all the members know and care for each other, bonding through common difficulties, life events, death and births.
Other issue, which is actually not that "old" - but for the past hundreds of years we have lost the contact with natural birth and death. People used to see, witness and care for the just born and the just deceased. All socializing was educational, all play was educational, all actions were emotionally binding. There was no sending a child to a stranger to learn the basic social rules, survival knowledge, knowledge about animals and plants. it was passed from one generation to another, naturally.
Just another aspect of the social interactions we have now. There are still cultures and communities that live with a different style, but especially in America it's very strong conflict. I am talking about the cult of individual achievement. The emphasis on an idea, that all depends on you, you are responsible, you have to do everything. One person is seen as the winner, as if s/he didn't come up on the backs of others. On the other hand in other cultures, especially more traditional, the emphasis is on the group, teamwork, team achievement. The success is common, no need for individual rat race.
Of course the flip side is the danger of canceling any right to individuality and being forced to give up own wants/dreams for the sake of the needs of a group.