The sentence that best helps develop the idea expressed in paragraph 2 is:
"Thanks to this analysis, the researchers were able to narrow down their original list of 3,000 genes to 43 specific sequences that might have contributed to Lonesome George’s long, disease-free life."
This sentence directly relates to the research on Lonesome George's genetic material and emphasizes the efforts made to identify the genetic factors associated with longevity, aligning with the focus on understanding what contributes to living a long life.