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Humans and Primates

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Humans and Primates
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What animals are humans' closest cousins?

Looking at our evolutionary tree, our closest relatives include the orangutans pictured here. Notice the way this mother cradles her child; they look very human-like. Orangutans are also highly intelligent. Notice the detail in the hand. In the wild, they can create and use tools.

Humans and Primates

The great apes are the members of the biological family Hominidae, which includes four living genera: chimpanzees, gorillas, orangutans and humans. Among these four genera are just seven species, two of each except humans, which has only one species, Homo sapiens.

Characteristics

The Great Apes are large, tailless primates, ranging in size from the pygmy chimpanzee, at 66-88 pounds in weight, to the gorilla, at 300-400 pounds ( Figure below ). In all species, the males are, on average, larger and stronger than the females.

A Western Lowland gorilla, member of the great apes. The gorilla is the largest of the hominids, weighing up to 309-397 lbs.

Most living primate species are four-footed, but all are able to use their hands for gathering food or nesting materials. In some cases, hands are used as tools, such as when gorillas use sticks to measure the depth of water ( Figure below ). Chimpanzees sharpen sticks to use as spears in hunting; they also use sticks to gather food and to “fish” for termites.

Tool using in a primate. A gorilla uses a stick to determine the water's depth.

Most primate species eat both plants and meat ( omnivorous ), but fruit is the preferred food among all but humans. In contrast, humans eat a large amount of highly processed, low fiber foods, and unusual proportions of grains and vertebrate meat. As a result of our diets, human teeth and jaws are markedly smaller for our size than those of other apes. Humans may have been eating cooked food for a million years or more, so perhaps our teeth adapted to eating cooked food.

Gestation (pregnancy) lasts 8-9 months and usually results in the birth of a single offspring. The young are born helpless, and thus, they need parental care for long periods of time. Compared with most other mammals, great apes have a long adolescence and are not fully mature until 8-13 years of age (longer in humans). Females usually give birth only once every few years.

Gorillas and chimpanzees live in family groups of approximately five to ten individuals, although larger groups are sometimes observed. The groups include at least one dominant male, and females leave the group when they can mate. Orangutans, however, generally live alone.

Genetic and Behavioral Similarities

Gorillas, chimpanzees, and humans are classified together in the subfamily, the Hominidae, because they have more than 97% of their DNA sequence in common. This means that a similar percent of the amino acid sequences of the proteins will be the same, resulting in many proteins with similar or identical functions.

All organisms in the Hominidae communicate with some kind of language. They can also create simple cultures beyond the family or group of animals. Having a culture means that knowledge and behaviors can be passed on from generation to generation.

Specialized Human Features

Specialized features of Homo sapiens include the following:

  • small front teeth (canines and incisors) and very large molars relative to other primate species,
  • a fully upright posture resulting in bipedalism (walking on two limbs instead of four),
  • shortening of the arms relative to the legs,
  • increased usefulness (dexterity) of the hands,
  • increase in brain size, especially in the frontal lobes
  • and a decrease in bone mass of the skull and face.

Vocabulary

  • culture : Behavior and knowledge that is taught and passed on to succeeding generations.
  • omnivorous : Eating foods derived from both plant and animal origins.

Summary

  • The biological family Hominidae includes four living genera: chimpanzees, gorillas, humans, and orangutans.
  • Gorillas, chimpanzees, and humans have more than 97% of their DNA in common.
  • All organisms in the family Hominidae can develop language and culture.

Practice

Use the resources below to answer the questions that follow.

  1. Where do chimpanzees ( Pan troglodytes ) live geographically?
  2. In what type of habitat do they live?
  3. What tool are the chimpanzees in the video using?
  1. What do gorillas do when they approach each other or feel other gorillas are around?
  2. How is a gorilla family organized?
  1. Where do orangutans ( Pongo ) live?
  2. Are the orangutans in the video displaying learned or innate behavior? Think carefully, and remember certain behaviors can have aspects of both types of behavior.
  1. To what kind of habitat are gibbons adapted? Give specific reasons why you feel they are adapted to this sort of habitat? How does this make them different from other apes?
  2. Observe carefully the behavior of the chimpanzees, gorillas, orangutans, and gibbons in the above videos. List all the behaviors you think are similar to humans, and which groups you see exhibiting this behavior.
  1. How does human DNA compare to chimpanzee DNA?
  2. How much variation do you think exists in the human genome given the comparison to the chimpanzee genome?

Review

  1. What organisms share the same biological family as humans?
  2. How are humans like the other animals in the Hominidae family?

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