2

When cells replicate, there is the occasional transcription error. As a person ages, these transcription errors accumulate. The reason that a lot of the elderly develop cancer, is the DNA governing when to replicate, and when not to, becomes corrupted. Some cell continues replicating past when it would normally stop.

Suppose that we compare a 60 year old man impregnating a younger woman to a 30 year old man impregnating her. In the case of the 60 year old father, the increase in risk of the child developing cancer is not nearly their father's. This is despite the fact that the DNA in the father’s cells is much more corrupted than the DNA in the 30 year old man’s cells. EIf sex cells degraded as readily as other cells, then the human race might go extinct after a few generations due to genetic defects.

What protects sex cells (sperm) from experiencing the same degradation as other cells in the body?

3

Older paternal (and maternal) age in fact is associated with some increase in disease, though at fairly low rates.

Cancer is largely a disease of probability. One does not need to have mutations in all of their cells to develop cancer, just one. But a parent does not pass on all their mutations in all their cells, they pass on just one, which need not have any deleterious mutations at all, even if the parent has cancer themselves in some other part of the body.

If that one cell is defective in some way, it is less likely to be involved in creation of a successful pregnancy, and may lead to miscarriage. Therefore, the probabilistic process of reproduction tends to result in offspring from selection of healthier gametes.

I grabbed a reference from another StackExchange answer, Cochran and Harpending 2013, which estimates that fathers pass on about 25+2(age−20) novel mutations. Many of those mutations will have no effect at all; those that do will be more common with older fathers.


Cochran, G., & Harpending, H. (2013). Paternal age and genetic load. Human biology, 85(4), 515-529.

de La Rochebrochard, E., & Thonneau, P. (2002). Paternal age and maternal age are risk factors for miscarriage; results of a multicentre European study. Human reproduction, 17(6), 1649-1656.

Jones, K. L., Smith, D. W., Harvey, M. A. S., Hall, B. D., & Quan, L. (1975). Older paternal age and fresh gene mutation: data on additional disorders. The Journal of pediatrics, 86(1), 84-88.

Sipos, A., Rasmussen, F., Harrison, G., Tynelius, P., Lewis, G., Leon, D. A., & Gunnell, D. (2004). Paternal age and schizophrenia: a population based cohort study. Bmj, 329(7474), 1070.

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