A finding here ties into research suggesting that life can be lengthened through selective breeding at later ages - this, like the response to calorie restriction, is a form of metabolic variability that may have evolved to make a species better able to adapt to changing environmental circumstances: "Children and even grandchildren of older fathers may live longer than children of younger men. ... Scientists found that children born to fathers between the ages of late 30s to early 50s inherit longer 'telomeres' or tiny protective caps on the ends of chromosomes that protect against aging degeneration and disease. ... Researchers measured the telomere length of DNA by using blood samples collected from 1,779 young Filipino adults and their mothers and determined the ages of the children's fathers and grandfathers. Study results show that a person's telomeres became longer not only with their father's age at birth, but also with their paternal grandfather's age at their father's birth, meaning that the longevity effect is amplified over the generations. ... The findings suggest that delayed paternal reproduction can lead to cumulative, multi-generational increases in telomere length in offspring which may promote longer life. Researchers also believe that longer telomeres may delay sexual development, and instead invest energy into the extra resources necessary to maintain healthy functioning at more advanced ages. ... late fatherhood may serve as a sigh that mortality rates are low. ... If your father and grandfather were able to live and reproduce at a later age, this might predict that you yourself live in an environment that is somewhat similar - an environment with less accidental deaths or in which men are only able to find a partner at later ages. In such an environment, investing more in a body capable of reaching these late ages could be an adaptive strategy from an evolutionary perspective."