Human Being. Human beings are mammals that, biologically, are closely related to the great apes (orangutans, chimpanzees, and gorillas). Human beings live in almost all parts of the earth. They can reason and plan, and can therefore readily adapt to environmental changes. In this sense, they are biologically the most successful species of animal.
From the point of view of most religions, a human being is the supreme product of creation, and has a unique relationship with the Creator. According to Judaism, Christianity, and Islam, humans were created in the image of God, and are composed of both soul, or spirit, and body. .
In comparison with other mammals, human beings are physically mediocre. Many mammals, for example, are stronger or more agile than humans, and many have far keener senses. Some anthropologists believe that this physical mediocrity is in part responsible for human beings' biological success. Not able to compete physically, they were able to survive by the development of tools, the use of fire, and the establishment of complex social interactions.
A complete biological classification of a human being is:
In terms of physical traits, there are more similarities than differences between humans and apes, and some zoologists think that human beings should be classified as belonging to the ape family. However, most researchers agree that humans have traits that are sufficiently unique to place them in a separate family, Hominidae.
The human skeleton and muscular system are well adapted to bipedalism (moving on two feet). The spine has a series of curves, forming an elongated “S.” This springlike shape makes it possible for the spine to absorb shock that would otherwise be transmitted to the brain. Human beings are able to keep an upright position and to carry their heads erect. A human's legs and feet are specialized for locomotion; the arms and hands, for manipulation.
A human being's facial profile is vertical, and its most prominent feature is the nose. The most important physical trait of human beings is a relatively large cranium, or brain case, and a large and specialized brain. The ratio of brain volume to the volume of the spinal cord is an indication of intelligence in animals—that is, the larger the ratio, the more intelligent the animal. The ratio is about four times as great in humans as it is in apes. .)
A human's size varies according to race and individual. Normal heights range from less than 5 feet (1.52 m) for the pygmies of the Congo region of Africa to 6 1/2 feet (1.98 m) for the males of the Watusi of Rwanda and Burundi. Color of skin and eyes, and color and texture of hair, also vary according to race and individual.
The main substance of the human body, accounting for 70 to 85 per cent of its weight, is water. As shown in the table below, 99 per cent of the body is made up of six chemical elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.
Human beings are land animals, and anthropologists believe that they were originally tropical forest dwellers. Many humans live in family groups, which may be extended beyond the parent-child group to include other relatives. Young human beings are slow to mature and are cared for by adults for a long period. Humans are omnivorous—they eat both plant and animal matter.
The highly developed brain of human beings is responsible for their ability to think in abstract terms, to reason, and to understand and use symbols. Through both spoken and written language, they have knowledge of their history and are able to communicate with their own and future generations.
The intellect of human beings has helped them to produce complex cultures and advanced technology, and to create and appreciate art, music, literature, dance, and drama. Humans are curious not only about the world around them, but about their history, their future, and the ultimate meaning and purpose of life.
The earliest known hominids (humanlike creatures) appeared about 4,000,000 years ago. They used stones as tools. During the Glacial Period, they gradually were replaced by more advanced types—sometimes referred to as “primitive men”—who shaped their stone tools and used fire. Humans of an unmistakably modern type appeared about 100.000 years ago. Where they originated, and how they developed from earlier types, is not clearly understood.