Longer telomeres in the somatic cells of an individual have been regarded as a marker of youth and biological fitness within a population. Yet, several research groups have reported the surprising findings of longer telomeres in the germ cells of older men, which translated into longer leukocyte telomere length in their offspring. Although all these studies were purely cross-sectional, a longitudinal trend in the aging testes of individual males was taken for granted. Recently, a high-profile study reported a negative birth-cohort effect on leukocyte mean telomere length in human populations, namely the progressive loss of telomeric sequence between healthy human generations. This is what I based my theory of telomere-driven macroevolution on, 12 years ago. On the basis of published data on telomere length inheritance, I identified the source of human intergenerational telomere erosion in the female germline. Accordingly, because of the resulting birth-cohort effect, there is no need for any paradoxical telomere lengthening in older men's gonads to interpret the old-father-long-telomered-offspring data.
Keywords: Alternative lengthening of telomeres; Birth-cohort effect; Intergenerational telomere erosion; Telomerase; Telomere lengthening; Telomeres.