To solve this problem, we need to determine which of the given hominid species had the smallest brain capacity. Let's analyze each option:$\newline \bullet$Homo erectus:$\newline$ - Homo erectus had a brain capacity ranging from approximately 600 to 1100 cubic centimeters (cc).$\newline \bullet$Homo sapiens:$\newline$ - Modern Homo sapiens have a brain capacity of about 1200 to 1600 cc.$\newline \bullet$Homo neanderthalensis:$\newline$ - Neanderthals had a brain capacity ranging from about 1200 to 1750 cc, often larger than modern humans.$\newline \bullet$Homo habilis:$\newline$ - Homo habilis had a brain capacity ranging from approximately 500 to 600 cc.$\newline$Based on this analysis, Homo habilis had the smallest brain capacity among the options provided.$\newline$Therefore, the correct answer is Option 4: Homo habilis.