Answer: APES

AnswerCrossword Clue
APESDr. Zaius and others
APESTarzan's posse
APESDian Fossey study
APESOur cousins
APESOur closest kin
APESSimians
APESAnimals studied by Yerkes
APESOur forebears, per Darwin
APESSiamangs, e.g.
APESHumorously mimics
APESFossey's focus
APESTarzan's clique
APESDoes an impression of
APESGoodall subjects
APESLummoxes
APESGibbons, e.g.
APESParodies
APESGaloots
APESMocks by imitating
APESPalookas
apesAPE, to mimic (to imitate (to copy (to imitate)))
APES"The IRS ..." (Willie Nelson album)
APESGibbons
APESCopies
APESEdgar Rice Burroughs characters
APESMimics
APES"2001" characters
APESFollows suit
APESImitates
APESDoes a takeoff
APESJungle critters
APESBig lugs
APESCaesar's soldiers, in a film franchise
APESCaesar, Koba, and Maurice in a 2014 film
APESBig galoots
APESCornelius and Zira
APESParrots
APESZoo section
APESTarzan's family?
APESNatural mimics