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 supports the idea of using Lonesome George's genetic material to understand the factors contributing to long life, as it describes a specific outcome of the research that relates directly to the study of longevity.