Just vaguely pointing to genes and biochemistry doesn't constitute an explanation to the questions in the OP anymore than observing a falling apple explains gravity.If you're talking about human behavior, wants, needs, tendencies, inclinations, etc, which is based on some combination of biology, genetics and neurology, then, yes, I do believe there is a science of human behavior and with the correct understanding of biology, neurology and genetics (all of which I'd say are "science") we can answer questions about how we should live, what gives meaning to our lives and why, etc.
In fact, there is a genetic component to divorce, even.
Other animals in the history of life have had genes, some were sentient, and at least one other hominid had bigger brains than Homo sapiens.
The development of complex religion, ethics, art, aesthetics, abstract contemplation proceeded much faster than we typically see in an evolutionary biological time scale.
Speculating that someday, some way, somehow science will explain and answer the four questions in the OP is strictly the realm of conjecture and guesswork.