Why is it that twins, who share the same genes,
have different diseases and different life spans?* NY Times discusses.
Quote: Life spans, says James W. Vaupel, who directs the Laboratory of Survival and Longevity at the Max Planck Institute for Demographic Research in Rostock, Germany, are nothing like a trait like height, which is strongly inherited.
ďHow tall your parents are compared to the average height explains 80 to 90 percent of how tall you are compared to the average person,Ē Dr. Vaupel said. But ďonly 3 percent of how long you live compared to the average person can be explained by how long your parents lived.Ē*
ďYou really learn very little about your own life span from your parentsí life spans,Ē Dr. Vaupel said. ďThatís what the evidence shows. Even twins, identical twins, die at different times.Ē On average, he said, more than 10 years apart.
The likely reason is that life span is determined by such a complex mix of events that there is no accurate predicting for individuals. The factors include genetic predispositions, disease, nutrition, a womanís health during pregnancy, subtle injuries and accidents and simply chance events, like a randomly occurring mutation in a gene of a cell that ultimately leads to cancer.
The result is that old people can appear to be struck down for many reasons, or for what looks like almost no reason at all, just chance. Some may be more vulnerable than others, and over all, it is clear that the most fragile are likely to die first. But there are still those among the fragile who somehow live on and on. And there are seemingly healthy people who die suddenly.
Some diseases, like early onset Alzheimerís and early onset heart disease, are more linked to family histories than others, like most cancers and Parkinsonís disease. But predisposition is not a guarantee that an individual will develop the disease. Most, in fact, do not get the disease they are predisposed to. And even getting the disease does not mean a person will die of it.
If this article is to be believed,* nutrition, lifestyle, and chance events have more bearing on longevity than genes.* Large families may have some, but not all members who live past 90.** Comparing twins should illustrate the genes vs lifestyle arguments, if the study is done long enough.