atavistic

adjective3

1. •
   Of the recurrence of a trait reappearing after an absence of one or more generations due to a chance recombination of genes.

   • Although the heterozygote gives it an atavistic appearance, the gene is not atavistic. — 1889
2. •
   Of a throwback or exhibiting primitivism.

   • They made me feel that I was alive in the nineteenth century, a sort of atavistic remnant, a romantic shred […] — 1934
3. •
   Relating to earlier, more primitive behavior that returns after an absence.