If you never do things alone, I suspect you don't read books anyway. So I'll just go ahead and ignore any advice from you about what books I should or shouldn't read...
Could it be that books are the technology that made being alone possible? Apart from monks, have people been alone before the invention of books? Without books, would people learn to stay by themselves and make it a habit?
People have spent a multitude of hours doing other activities alone as well--painting alone, looking at the stars alone, practicing dance alone, using the restroom alone...
No need to see everything in black and white. There are a lot of shades of gray. You're correct that humans work in groups, doing things alone is inefficient, harder and possibly dangerous.
But being alone and learning to deal with your own feelings and thoughts is a good way to mature and know oneself better. Also, there are a lot people that need time alone to recharge and regain energy that they spend socialising and interacting with people.
So there are benefits of being alone.
BTW: haven't read the book and do now know what exactly it is about.
This book is about learning how to entertain yourself alone during your free time, not mandating that you only recreate alone, much less disconnecting yourself from society altogether.
People without social connections die earlier statistically, but that can be explained by outside effects (e.g. if you do not live in a family structure, chances are you'll be found too late after suffering from a heart attack or stroke; less people around you means less immunisation for common diseases; no friends means a house fire may stress you out more and you becoming homeless ...). Calling that "most would be dying from no social connections" still seems a bit a far reach.
Also, the "we need to be around people at all times" seems to be less determined by genes, but by culture: people in other cultures and at other times seem to have been fine with extended periods of no human contact. Think the 'forest dwellers' in Hindu culture, or monastic hermits.
I wonder if the causation is reversed when people talk about living a shorter life with fewer social connections. If someone has mental health issues or substance abuse problems they're likely burning through their social connections and their health at the same time.
To prove humans need social connection, all you have to do is look at the heartbreaking (and thankfully rare) cases of children that grew up completely neglected and sequestered. As in, locked in a room with no attention for the first decade of their life. When they're discovered, they're not what you think of as human. They never developed language. They never developed the ability to form relationships. They know nothing about the world and have virtually never interacted with anyone. There is no amount of therapy that will ever turn these young people into functional humans and in the case I remember most vividly, they will never develop any real language or ability to communicate either.
Your argument is different from your explanation. You're speaking about complete isolation. Children need some socialization for them to adapt to the modern world. That's different than proving humans need social connections in the long term. Almost all people want some form of socialization, some less, some more. It's extremely rare a person would want complete isolation forever in perpetuity and I say that as a person who can only handle about an hour of socialization before I want to climb in a hole. What no one talks about is when too much socialization can impair growth.
But that's extreme. We don't go back to living in a cave and bashing each other's skulls in with rocks, just because that's where evolution took us. Our minds are above and beyond some aminoacids (or whatever) now.
