I figure that 60 is a good target to call it old - before that is late middle age, and after that age starts killing people off. Besides, 60 is 150% of our "natural" ie sans modern health care age. In the good old days - read neolithic and older, we tended to die when we were in our late 30's/early 40's. We had fulfilled our biological imperitive by then, and imparted our wisdom and strength to the next generation. Any age after that was gravy. The modern era - read anti-biotics and sterilized surgical/anesthetic options coupled with true dentistry and an awareness of general health and nutrition - allows us to impart our wisdom and strength to the generations following our children by keeping us viable and vital beyond the 40-45 year limit.
Of course, I will be 48 next month, a grandfather of a sweet little girl, and prefer the tag middle-aged over old - but that's just me
