As Hominins Diverged from Other Primates, Which of the Following

Question

As hominins diverged from other primates, which of the following appeared first?
A) reduced jawbones
B) language
C) bipedal locomotion
D) the making of stone tools
E) an enlarged brain

Accepted Answer

The oldest evidence of bipedalism, which is a defining characteristic of hominins, dates back to approximately 5-7 million years ago, making it the earliest feature to appear in the evolution of hominins.

Answer A, D, and E all appeared later in hominin evolution:
A) Reduced jawbones developed later as hominins' diet changed to include more soft foods that required less chewing.
 
D) The making of stone tools began around 2.6 million years ago with the appearance of Homo habilis, one of the earliest known human species.

E) An enlarged brain is a hallmark of later hominin species such as Homo erectus and Homo sapiens, and did not appear until more recently in hominin evolution.

B) Language is difficult to pinpoint as its evolution is not clearly documented in the fossil record, and may have developed gradually over time.