. Scientists from Norway’s University of Science and Technology and University of Glasgow, Scotland, have found that DNA linked with ageing and longevity changes when body sizes increase. They based their conclusions on wild sparrows. The research was published by Professor Pat Monaghan (Regius Chair of Zoology, University of Glasgow) and his colleagues in the scientific journal Proceedings of the Royal Society Biological Sciences. Larger animals tend to live longer lives than those of smaller species – for example, an elephant can live longer than mice or rabbits. However, within many species larger people tend to die sooner than their smaller cousins. The structures at the ends (blue) of chromosomes are called Telomeres and protect genetic material during cell division. The telomeres prevent chromosomes ‘fraying’ by preventing them from binding to other chromosomes or fusing with each other. Image: Telomeretesting.net. A Jack Russell, for example, has an average life expectancy that is significantly longer than a St. Bernard. According to the authors, taller individuals are more susceptible to diseases. The same goes for human beings. Taller individuals are more likely to develop cancer and other diseases. Scientists had never been able fully to explain why this was until this research. Telomeres may have the answer. Telomeres are a section of repeating DNA located at the ends a chromosome. They protect that end from damage, much like shoelaces’ protective caps. The scientists studied wild sparrows living on an island called Leka in Norway. Researchers found that sparrows with larger skeletons have shorter telomeres than those with smaller skeletons. The average lifespan for a Great Dane is 8 years. A Chihuahua’s life expectancy is at most 14. The association was established during the period of selective breeding in Leka, which saw sparrows grow even larger. According to the authors, sparrows that were larger had shorter telomeres. A shorter telomere is linked to slower ageing and more disease. Telomeres in all animals (including humans) erode with time. Shortening telomeres has been associated with increased disease risk including cancer and older age. If your telomeres are naturally longer, it is likely that you will have a lower risk for disease and biological ageing than other people with shorter telomeres. People who are shorter tend to live longer than those who are taller. These results could help to explain an old paradox that puzzled biologists for years. Being larger can give an animal a competitive edge – it protects predators and makes prey easier to catch – so why not just grow bigger and better? One reason is that growing larger may lead to faster ageing and more telomeres being lost. a shorter lifespan. Monaghan was the supervisor of the telomere analysis. He explained that “growing a larger body requires cells to divide more. Professor Monaghan, who conducted the telomere analysis explained that telomeres are eroded more quickly and tissues and cells function less well. “This could also be due to DNA damage from growing faster. While being large can be a good thing, this research shows it can come with its own costs. Thor Harald Ringsby is an associate professor of population ecology at Norway’s University of Science and Technology. He said that the results of the study were very interesting and wide-reaching. These results were especially fascinating because they were obtained in natural populations. “The decrease in telomere sizes that occurred after an increase in body weight suggests that there is an important mechanism to limit body size evolution in wild animals populations.” This study was supported by both the Research Council of Norway (RCN) and the European Research Council. Citation: “On Being the Right Size: Increased body size is associated reduced telomerelength under natural circumstances,” Thor Harald Ringsby. Henrik Jensen. Henrik Parn. Thomas Kvalnes. Hakon Holand. Ingerid Julie Hagen. Bernt Ronning. Bernt-Erik Saether. Pat Monaghan. Proceedings of the Royal Society Biological Sciences. Publication 2015. DOI: 10.1098/rspb.2015. 2331.
