… and, somatic cell lines that are cancerous ten to get more rapidly shortening telomeres. And yes, the link between cancer and shortened telomeres is the main link.

Your point about telomere shortness and cancer is, of course, the whole point of the research; I mention the link between longer telomeres and/or increased telomerase activation and cancer for completeness. It has not been demonstrated and how this would work is unclear, but I refer you to Weinstein and Ciszek, (2002) if you want to know more about that. It probably isn’t of any great importance, but it does bring up the basic question: Why aren’t all telomeres very very long?

The cancer causing explanation (just noted) is one possibility, another is energy use (longer telomeres = more energy used) and a third is that there is simply not selection against short telomeres or effecasious telomerase activity in lineages of short lived organisms, and thus some long lived organisms that evolved from short lived ones (like us) are unlucky (phylogenetic constraints can be a drag).

See Dan Eisenberg’s paper “An evolutionary review of human telomere biology” (American journal of human bilogy) from 2010 for a great overview of these questions.

To learn more you might want to check out Dr Ed Park MD MPH on youtube.