"Without being sensational, I'd say this is an opportunity for us to answer the question, why we're mortal, or at least to test it," Walker said. "And if we're wrong, we can discard it. But if we're right, we've got the golden ring."
If the gene -- or complex of genes -- is identified, Walker plans to test laboratory animals to determine whether the gene can be switched off and, if so, whether it will cause the animal's aging to slow.
In the long term, the idea that the aging process might somehow be manipulated raises serious questions about what human beings might do with that knowledge.
"Clearly, that's the science fiction aspect of it," said Walker, describing the social and ethical dilemmas that would arise. "We can't have continued reproduction and people who don't age."
One possible reason to slow the aging process, Walker suggested, would be to allow astronauts to travel in space for long periods of time. "But right now, it's only conjecture," he said.
Neither Walker nor Pakula, her doctor, can speculate how long Brooke's life might be. "That's more of a crystal ball question," Pakula said. "I think there's no way of knowing. "
The visual evidence of that unpredictable future is always there in the family pictures -- photographs in which everyone but Brooke is aging.
The Greenbergs are fascinated by the promise that a scientific breakthrough may stem from Brooke, whose own life is governed by the most basic elements: food and shelter; a family's love; and their ability to see in her far more than meets the eye, having come to terms with the prospect that she will never grow up.
"We love her just the way she is," Melanie Greenberg said. "We don't want to change her."
Added Howard Greenberg, "Brooke is the nucleus of our family. What if Brooke holds the secret to aging? We'd like to find out. We'd like to help people. Everybody's here for a reason. Maybe this is why Brooke is here."
For more of Brooke's story, watch the documentary, "Child Frozen In Time," Sunday, Aug. 9 at 10 p.m. on TLC.