1. Within the primate order, humans are most closely related to the anthropoid apes ( the African chimpanzee and the gorilla and the Southeast Asian orangutann and gibbon), and of these, to the chimpanzee and the gorilla.
According to the sentence ' the chimpanzee and the gorilla' are more general than anthropoid apes. That is, anthropoid apes are included in the chimpanzee and the gorilla.
You got this part backwards. The anthropoid apes is a more general term than the chipanzee and the gorilla, that is why they come behind and between parenthesis, because you are being given an example of two types of anthropoid apes. Therefore, there is no contradiction.