Longevity varies in twin types

Question: Do identical twins or fraternal twins live longer? Both sets come from the same gene pool and are exposed to the same environment, more or less, so any difference would seem puzzling.

Answer: Puzzling for sure, but going by recent reports, identicals average 82 years longevity, fraternals 80.5. The data come from the World War II Veterans Twins Registry, including some 12,000 IDs and 15,000 frats born between 1917 and 1927, says University of California-Berkeley biologist Malcolm Zaretsky in the Journal of Gerontology. He looked at various environmental factors and found that longevity was greater for identicals who communicated by phone or mail at least once a month; but for fraternals, it didn't seem to matter if they stayed in touch. One factor for the identical twins may be that they tend to exercise more and smoke less and do this as a tandem.

Social relationships and networks are well-established health and longevity boosters, and somehow the genetic closeness of the identicals makes their special bond more beneficial, so much so in fact that the death of one of them is the one thing sure to nullify the other's longevity boost compared to fraternals.

Based on various studies, longevity has a heritability of only 20 percent to 30 percent, meaning social environment/lifestyle are much more important. The take-home message, says Stanford University gerontologist Walter M. Bortz, M.D., is that "It ain't the cards you're dealt, it's how you play the hand."

Question: In a "Pet IQ Challenge," would your dog or cat come out ahead?

Answer: Intelligence tests for animals — the speed at which an animal can learn to perform a task — have been around since early last century, says Nicholas Dodman of Tufts University School of Veterinary Medicine. Require a cat to figure out it must pull a string to receive a reward, and it will do so in time; a dog, not being so dexterous, will take much longer to do the same task. That is, the test you use (cf. the Ellis Island experience for would-be immigrants) will to some extent determine the animal's performance.

This is true even within breeds. Tracking dogs excel when asked to locate something rapidly using sense of smell.