I think Christians, Buddhists, evolutionary biologists, statisticians, and developmental economists are right. There is no way to make sense of a life in isolation. The notion of individuals breaks down under scrutiny.
One of the lessons of systems thinking is that systems emerge out of the interactions of parts.
Systems thinking advocate Russell Ackoff was fond of the analogy of a car to illustrate this point. A car can get you across town. The tires alone can't do that. The steering wheel cannot. The engine, alone, will just sit in your driveway and roar. What makes a car a car is the interaction of its parts, not the actions of its parts in isolation. The quality of a car emerges out of the interaction of its parts.
Your life is a system. What does it mean to be human? No species is born more helpless. A horse can run within minutes of being born. It takes us a year to be able to stagger and another year before we can talk about it. Humans are helpless for the first 10 to 25 years of life. Put aside the necessity of biological parents who "create" you. You don't even get to be human without the assistance of others for the first decade or two of life. We're little different from other primates without our speech and tools and to learn those adds another layer of dependence on others. Language does not emerge from an individual experience; it comes out of interaction with others.
To understand the culture we're born into, the options for work, and the skills needed to contribute to a working society adds yet another layer of dependence.
An individual life is an emergent property. It comes out of interaction with others, it has a particular place in history, economic development, and culture. It does not exist in isolation and to even speak of it as if it does is to strip it of all that defines it. We get defined through relationships and who we can be is hugely dependent on everyone else. Who a peasant woman in 1318 could be is vastly different than who an urban woman in 2018 can be. Each emerges out of her time and place. The notion that either is an individual who chooses her own life is a popular myth but a myth nonetheless.
Paradoxically, this is why it is so important to be an individual as defined in popular myth. The way progress works is that it sends tentacles out into the future in the form of individuals. Some paths work out and some hit dead ends. Your effort to become someone new and different becomes a starting path for those who come along later, even though that effort is absurd to even contemplate in a vacuum. Our life is the variation in the distribution of the system and through our life the distribution has the potential to change over time.
Because the system is twice emergent. Your life emerges out of a system that is a complex mix of culture and technology and that system emerges out of the complex mix of who people were and aspire to be. You define the system that defines you.
It's not paradox but rather perspective that makes two contradictory things true at once: lives emerge out of systems and systems emerge out of lives. The two options that are illusory are the options to believe that you define your own life or that you don't define the world you live in. This means that we have to work through others to even have the hope of changing ourselves. And others have to work through us for any hope to change themselves. We are inescapably created by the world around us and create that very world, sometimes in ways that have less to do with who we ever get to be than who other people get to be - now and in the future.