Old man, well into his eighties, goes to a doctor for a regular checkup.
The doctor examines him, makes several tests, looks at him and he can't believe what he sees. He says:
"Old man, this can't be true! You're old, but you're healthy as a teenager. No hypertension, no elevated sugar levels, your ECG is perfect... How is that possible?"
"Well" old man replies "probably because I'm physically active. You see, I walk every day, I go fishing regulary..."
"No" the doctor interrupts him "that couldn't possibly explain this phenomenon. This must be genetic. Tell me, how old was your father when he died?"
"My father is not dead! - the old man replies - He's alive and well just as I am. We go fishing together."
The doctor is gobsmacked. With a shaky voice, he asks:
"How old is he?"
"Almost a hundred. He married young."
"Wow! This is phenomenal! Now, how about your grandfather? Can you remember how old was he when he died?"
"He's not dead either! He's almost 120."
Now the doctor is skeptical.
"I guess he too goes fishing with you and your father?"
"Oh, no, this week he'll be at home, he's preparing for his wedding"
"He's getting married at 120?"
"Well, he doesn't really want to, but his parents are nagging him..."