Atavistic

 
The term atavism (derived from the Latin atavus, a great-grandfather's grandfather; more generally, an ancestor) denotes the tendency to revert to ancestral type. An atavism is an evolutionary throwback, such as traits reappearing which had disappeared generations ago.

Atavistic is the adjective from the noun atavism and is more commonly used. It refers to something being a throw-back to earlier times; to remote ancestry or to a primitive nature.

"The noise she made as she threw herself on the bed was atavistic."