Final answer:
Non-human apes have complex social structures with sexual dimorphism in Old World species and significant DNA similarities among Great Apes. Apes evolved from catarrhines and are distinguished from monkeys by their size, lack of tail, and knuckle-walking. The behavior of non-human primates shows biological flexibility and variability in social and gender expressions.
Step-by-step explanation:
The social arrangement of non-human apes includes a variety of family structures, mating behaviors, and societal roles. In Old World species, which encompasses monkeys of Africa and Asia, there is often significant sexual dimorphism, indicating a difference in size between males and females which may suggest that historically a single male defended multiple females. When it comes to the Great Apes, which includes chimpanzees, gorillas, orangutans, and humans, there is over 97% DNA similarity, and all are capable of developing language and culture, highlighting their advanced cognitive abilities.
Apes, evolving from the catarrhines about 25 million years ago, are noted for their larger size compared to monkeys, absence of a tail, and for walking on their knuckles as opposed to the palms in monkeys. The apes are also divided into the lesser apes, such as gibbons and siamangs, and the Great Apes, which includes the genera Pan, Gorilla, Pongo, and Homo. These classifications demonstrate the diversity and complexity among primate species.
Despite similarities, it is crucial to acknowledge that behavior in non-human primates cannot directly assign what is 'natural' for human males and females due to the biological flexibility and variability of social expressions of gender and sexuality in apes. This highlights that primates, including humans, are quite flexible in their social structures. Finally, the great apes, which are represented by just seven species across four genera, demonstrate intricate social systems, intensified by the fact that most primate groups are composed of related females with males joining the group.