MEN who have children later in life may pass on changes acquired from their environment, a phenomenon reminiscent of Lamarckian evolution.
French naturalist Jean-Baptiste Lamarck thought that if organisms changed their bodies during their life to adapt to their environment, those changes could be passed to children. Giraffes stretching their necks to reach tall trees, and then passing longer necks on the next generation, is a classic example of this incorrect theory of evolution.
We now know organisms evolve through random DNA mutations: giraffes with mutations that caused longer necks passed these changes to their offspring. But a study of children of older dads suggests it may be possible to pass adaptations to subsequent generations in other ways.
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Dan Eisenberg at the University of Washington in Seattle and his team have studied telomeres, stretches of repetitive DNA at the ends of our chromosomes. These shorten each time a cell divides, so usually get shorter over a lifetime. If telomeres get too short, cells may stop dividing or even die.
A woman鈥檚 eggs are all made before she is born, but the cells in men鈥檚 testes divide throughout their lives. Because we inherit telomere lengths from the egg and sperm cells that make us, the children of older fathers should in theory have shorter telomeres, but they don鈥檛.
This is probably because an enzyme called telomerase, which extends telomeres by adding more DNA to them, is very active in the testes. Several studies have shown that sperm from older men have longer telomeres than average.
This may enable older men to reproduce without having children with dangerously short telomeres. Because telomerase adds DNA to a chromosome, it may be possible that they pass this acquired, non-genetic trait 鈥� longer telomeres 鈥� to offspring.
Studying the DNA of nearly 3000 grandparents, plus their children and grandchildren, Eisenberg鈥檚 team found that this may be the case. A child鈥檚 telomere length correlates with the age at which their fathers and grandfathers reproduced, Eisenberg told a meeting of the American Association of Physical Anthropologists in Ohio.
Because telomere length may play a role in longevity, this could represent older fathers adapting their children鈥檚 DNA for an environment in which it may be possible to live a longer life, says Eisenberg. 鈥淭he father鈥檚 age at reproduction is likely to be containing a signal about what the recent environment was like,鈥� he says. 鈥淚t breaks some of the ways biology is supposed to work.鈥�
Eisenberg says that, while the idea the environment influences DNA in this way isn鈥檛 yet proven, it should be taken more seriously. 鈥淚t could be a multigenerational signalling mechanism. It鈥檚 not so crude as the giraffe鈥檚 neck. But there鈥檚 a similarity.鈥�
While Lamarck had fully functional anatomical systems in mind, it is possible that there is a Lamarckian parallel here, says Steven Leigh at the University of Colorado, Boulder.
