People seem made about my comment... Look at at this way. What are the odds that the one and only animal you bring back has a terminal lung defect?! You don't wanna gamble a theory with bad odds! Meaning: probably the lung defect issue was a common thing for this specimen, and they had a difficulty time maintaining a steady population. This can happen in the evolutionary path. Even human tribes have been experienced high mortality rate because of a genetic decease. Don't take it personal, animals can be sick too.