ataktiline

Ataktiline is an Estonian term used to describe atavistic traits—characteristics that reappear after being absent for many generations, mirroring ancestral states. The concept is commonly discussed in biology, paleontology, and medicine when referring to the reemergence of features once widespread in distant ancestors.

The root of the term is Latin, with atavus meaning ancestor. In Estonian, the suffix -iline forms adjectives, producing ataktiline to describe things relating to atavism.

In biology, atavism refers to the recurrence of ancestral features due to the reactivation of dormant genetic networks or altered regulation of developmental pathways. It is not simply the straightforward inheritance of a single trait; rather, it reflects the complex interplay of genetics, development, and evolutionary history.

Examples commonly cited include human tails or caudal appendages and supernumerary nipples, which are considered human atavisms. In whales, occasional reexpression of hind-limb structures or pelvic bones has been cited as a vestigial echo of terrestrial ancestors, illustrating how atavistic traits can reveal deep evolutionary connections.

The concept of atavism helps scientists study evolutionary history and the regulatory architecture of development. In broader usage, atavistic can also describe the resurfacing of ancient patterns or impulses in culture or behavior, extending the idea beyond strict biology.