Homo habillis
Homo erectus
Homo neanderthalensis
Homo sapiens
A. Homo neanderthalensis had the brain capacity of about 1450 cc.
B. Homo habillis had the brain capacity of about 700-800 cc.
C. Homo erectus had a brain capacity of about 900 cc.
D. Homo sapiens have a brain capacity of about 1400 cc.
Hence Homo habillis had the smallest brain capacity. So, the correct answer is 'Homo habillis'.