TIL: Atavism

[adjective] – atavistic
Reverting to or suggesting the characteristics of a remote ancestor or primitive type.
Of, relating to, or characterized by atavism;

[noun] – atavism
a tendency to revert to something ancient or ancestral.

From Latin atavus - 'forefather'

https://en.wikipedia.org/wiki/Atavism

"So much of their business was done via e-mail that the phone was
almost unnecessary–a sort of quaint atavism that nobody thought to use first–but this morning the ringing had been ceaseless."

• DEBRA GINSBERG, "WHAT THE HEART REMEMBERS"

Because the United States has proved successful in absorbing people from so many different backgrounds, the American political elite has, since the mid-20th century at least, tended to look on group identity as a kind of irrational atavism.
– PARK MACDOUGALD, "CAN AMERICA'S TWO TRIBES LEARN TO LIVE TOGETHER?"

"The Internet—tends to involve communication and interaction, and thus it tends to be specifically social: it tend to involve the thoughts, feelings, and actions of many individuals, pooled in some way to make them accessible to individuals, including me. The Internet thus facilitates the human capacity to be homo dictyous (network man), an innate tendency we all have to connect with others and to be influenced by them. In this regard, the Internet is both mind-expanding and atavistic."
– NICHOLAS A. CHRISTAKIS, "HOW IS THE INTERNET CHANGING THE WAY YOU THINK?"