Within the superfamily Hominoidea, there are two families: Family Hylobatidae (gibbons and siamangs), and Family Hominidae (great apes and humans). There are a number of traits that distinguish the two families:

Family Hylobatidae (Gibbons and Siamangs)

Gibbons and Siamangs are sometimes known as the "lesser apes", because of their much smaller size than the "great apes", and because their behavior is rather different, as well. Hylobatidae are only found in Southeast Asia.

Locomotion: Hylobatidae are the brachiators par excellence. Their movement through the forest is truly impressive, as can be seen in this video. Their skeletons reflect their adaptation for brachiation. Both their wrists and their elbows are shaped to allow flexibility and backward bending to a degree not possible in humans. Their very long arms (and short legs) are another reflection of that adaptation. Their skeletons reflect their brachiation in another way; wild gibbon skeletons have the highest proportions of breaks found in any primate. In other words, while they are the most amazing "flyers" of the primate world, they do occasionally go "splat". (This video is not of a gibbon, but it illustrates the point.)

Social Organization: Gibbons and siamangs form monogamous pairs. A male and a female mate for life, and live together in their territory, raising their young. In the mornings, they duet, a song that they use to announce their territorial claims. They will fight other gibbons to defend their territory.

Active time: Hylobatidae are active during the day, like all Hominoidea.

Habitat: Gibbons and siamangs live in primary forest. They are almost completely arboreal, spending their time almost exclusively in the high canopy.

Diet: Gibbons eat mostly fruit, along with leaves and insects. Siamangs eat a more balanced diet of leaves and fruit.

Family Hominidae (Great Apes and Humans)

Genus Pongo (Orangutan)

Orangutans are the only great apes in Asia. They are found only on the islands of Borneo and Sumatra. Of all the great apes, the orangutans are the least closely related to humans. Nonetheless, they show a number of traits similar to humans and other apes.

Locomotion: Orangutans are too big to be truly brachiators. They are often described as suspensorial, meaning they hang or suspend from branches, using all four limbs. When they are on the ground, which is seldom, they are quadrupedal.

Social organization: Orangutans are solitary. They are the only solitary apes. As is the case for all great apes, the males will display, meaning they make a big fuss, bellowing and shaking branches, in order to defend their territory, intimidate rivals, or assert their dominance.

Active time: They are active during the day, like all Hominoidea

Habitat: Orangutans are almost wholly arboreal, so they are found in rainforest environments, at all levels of the canopy. The market for palm oil is one of the biggest threats to orangutans, because it is destroying their habitat.

Diet: They mostly eat fruit, although they will eat leaves and insects, as well. They do not commonly hunt, but will eat meat if they can find it. They have been seen to use simple tools in the wild, such as stones to break open hard-shelled fruits and sticks to spear fish.

Genus Gorilla (Gorilla)

The gorilla is native to sub-Saharan Africa. Since humans are also a sub-Saharan African ape, we are close relatives of the gorillas, although chimpanzees are more closely related to us. The gorilla is the largest ape, and although they have a pop culture reputation for being fierce and aggressive, they are actually very quiet, peaceable, calm animals, especially when compared to the chimpanzee. Males do display, including thumping their chest and charging at challengers, but even the males are usually calm, perhaps because they have more limited opportunities for aggression compared to chimpanzees.

Locomotion: Gorillas are quadrupeds, with an adaptation called knuckle walking. As the name implies, knuckle walking refers to walking on the ape's knuckles (with the fingers curled under), rather than with the hand flat on the ground. Unlike chimps, which sometimes walk bipedally for short distances, gorillas don't stand up on their back legs, except when the males display by pounding their chests.

Social Organization: Gorillas live in single-male/multifemale groups. The one breeding male is called a silverback, and he literally has a silver back, a trait that comes with sexual maturity, not from great age. The group can be anywhere from 5 to 30 individuals, mostly females and their young. When male offspring reach maturity, they will be driven out by the silverback. They wander until they can kidnap a female or take over a group from another silverback. Although males fight to protect their territories and families, gorillas are less likely to engage in dominance behaviors in general. Males are very gentle with the young and will protect the group from predators, as well as conspecifics. The males are much bigger than the females (twice the size), as is common with single-male/multifemale social organization.

Active time: Gorillas are active during the day.

Habitat: Gorillas, particularly gorilla males, spend almost all their time on the ground. Males are so big they can't get into trees very well. Females and young, on the other hand, will spend the night in nests in the trees, but most of the day on the ground. They live in rainforest environments. While they were once found throughout lowland central Africa, today they are mostly restricted to upland environments because these are the areas that have not been deforested for agriculture.

Diet: Gorillas eat almost anything they can get. Their huge bodies require a lot of food to maintain, and since they don't eat a very high quality diet (that is, the foods they eat have a lot of roughage and aren't high in calories relative to the amount of energy it takes to consume them), they need to eat nearly constantly to get enough. They will eat leaves and fruit, but also bark, roots, vines, and a variety of other vegetation. They have been seen to hunt, but it appears to be a very rare activity, and meat is a very small amount of their diet. Like orangutans and chimpanzees, gorillas have been observed to use simple tools in the wild, such as a stick to "fish" for ants.

Genus Pan (Common Chimpanzee and Bonobo/Pygmy Chimpanzee)

The two species of chimpanzees are our closest living relatives. We are no more closely related to one species than to the other (they split from each other only about 2 million years ago, and our last common ancestor with both was around 7 million years ago). We share about 97% of our DNA with chimpanzees, although, to put that into perspective, I should note that we share nearly half our DNA with bananas. The chimpanzees are found in sub-Saharan Africa, with the common chimpanzee found farther north and over a wider range than the bonobo. Both species are much smaller than orangutans or gorillas. Males are around 3 feet tall and 85 lbs, while females are slightly shorter and lighter. Their level of sexual dimorphism is greater than in humans, but not as great as in gorillas. Bonobos, or pygmy chimpanzees, aren't actually smaller than common chimpanzees, they're just built more lightly, with longer legs. They look more eerily human than common chimpanzees.

Locomotion: Chimpanzees are quadrupeds. They brachiate through the trees, and knuckle-walk on the ground. They occasionally walk bipedally, especially if they are trying to carry something. This type of bipedal walking is found more often in bonobos than common chimpanzees. Chimpanzees sleep in nests in the trees, but the amount of time they spend on the ground depends on their habitat. If they live in savannas, they spend much of their time on the ground. If they live in dense rainforest, they spend much of their time in trees. Like humans, they are flexible in their behaviors.

Social Organization: Chimpanzees live in multimale/multifemale groups of 30-80 individuals. They have a well-developed dominance hierarchy, particularly among the male common chimpanzees. Males stay in the same group for their whole lives, and develop very close ties to their mothers. Females leave when they reach sexual maturity and join other groups. In common chimpanzees, the groups are highly excitable, and males frequently display. Males are dominant over the group and have complex political alliances that can be highly aggressive, both within the group and between groups. In one documented case, a community of chimpanzees split because it had gotten too large. The males from one of the groups hunted down and killed all the members of the other group, taking over their territory. Friendships and alliances are formed by grooming and sharing meat. Common chimpanzee males hunt in groups, mostly targeting colobus monkeys. They will share the meat with others to build political alliances.

Bonobos have a slightly different social organization. Although the general structure is the same (multimale/multifemale groups of 3-80, with related males at the core), the bonobos are not nearly as aggressive or excitable. Instead of fighting, bonobos use sex (video NSFW) as a major tension reliever. Although violence still does happen among bonobos, there has not yet been a documented case of bonobos killing each other. Unrelated females tend to band together, preventing male violence, and group leaders may be male or female. Meat sharing does not seem to be as frequent, but bonobos are not as well studied, especially in the wild, so it is hard to know what we may be missing. Females are more likely to hunt than males among the bonobos. They mostly hunt small antelope and have been documented to hunt with simple wooden spears.

Diet: The chimpanzees eat a higher quality diet than the gorilla. Most of their diet is fruit, but they also eat leaves, insects, nuts, and meat. Their hunting was discussed above, but it's important to recognize that meat is a very small amount of their diet. They don't eat nearly as much meat as humans do. Chimpanzees use a variety of tools to get food, including rocks to crack open nuts, and sticks for "termite fishing". Females are more likely to use tools than males, and most new tools are developed and popularized by females. This is true for a variety of tool-using primates, not just chimpanzees. Infants learn about tool use by watching their mothers.

Genus Homo (Humans)

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(seriously, we'll cover this the whole rest of the semester)