The term "prehuman" refers to the time before the appearance of human beings on Earth, which makes it difficult to find synonyms that accurately convey the same meaning. One possible option is "prehistoric," which refers to the period before written records were kept. Another option is "paleoanthropological," which is more specific to the study of human evolution. "Primate" can also be used to describe the prehuman era, as humans are technically classified as primates. Other possible synonyms include "protohuman," "pre-hominid," and "ancestral primate." While these words may not be exact synonyms, they can be used in context to describe the time before the existence of Homo sapiens.