Wikipedia claims "Over 8% of the human genome is made up of (mostly decayed) endogenous retrovirus sequences"[1]. So, it appears they are at least common enough

Wikipedia claims "Over 8% of the human genome is made up of (mostly decayed) endogenous retrovirus sequences"[1]. So, it appears they are at least common enough that we're all passing along endogenous viral elements[2] to our children (and we got them from our parents). [1] https://en.wikipedia.org/wiki/Noncoding_DNA#Repeat_sequences.2C_transposons_and_viral_elements https://en.wikipedia.org/wiki/Noncoding_DNA#Repeat_sequences... [2] https://en.wikipedia.org/wiki/Endogenous_viral_element https://en.wikipedia.org/wiki/Endogenous_viral_element