人教全日制普通高中英语（必修）高三UNIT14-2

Like all other living creatures, human beings belong to a group of other animals that share certain characteristics. Zoologists 1 place us in a group called primates 3, which include other mammals such as apes and monkeys. Among the key features found in primates are hands and feet that can grasp and often have opposable thumbs and toes. That means that primates are better than other animals at holding, moving and using objects. Indeed, many primates, most notably 4 human beings, have learnt to make and use tools. Primates also have a better sense of touch and the primate 2 brain is larger -- compared to body size -- than that of other animals. Depending on the size of the brain, primates are divided into two groups: higher primates (human beings and apes) and lower primates.

 

       There are some 183 species 5 of primates and they are also sometimes divided into two other groups: new world primates, which are small monkeys that live in trees, such as the spider monkey and the night monkey; old world primates include monkeys, apes and humans. They are bigger and spend more time on the ground.

 

       There are several important differences between apes and monkeys: apes have no tail, nearly all monkeys do; apes tend to be larger and walk more upright; apes use sight more than smell. Apes also have more developed brains and give birth to fewer young, which need a long time to grow up. Zoologists also make a distinction between great apes (including gorillas 6 and chimpanzees) and lesser 7 apes.

 

       Most primates are social animals that live in groups and communicate with each other. A few live alone. Gorillas live in groups of one male and several females, and chimpanzees live in groups of many males and many females. While their societies are different, they all communicate and behave in advanced ways. Primates use facial expressions, body language and sounds to express themselves and they can even use colour and smell to communicate. Sometimes they warn each other of danger, and they also communicate simply to keep in touch.

 

       Our closest relative among the primates is the chimpanzee, an intelligent great ape that lives in western and central Africa. Chimpanzees are about 50 centimetres to a metre tall and weigh around 25 to 50 kilogrammes. Males are larger than females and can be up to 1.2 metres tall and weigh 70 kilogrammes. Chimpanzees have very long arms and are covered with black hair. They use the same senses as we do and their feet and hands are similar to ours, except that chimpanzees still have opposable toes and can grasp things with their feet. Their diet is also similar to ours -- they eat meat and plants -- even if they sometimes feast 8 on things we may find disgusting, such as insects and ants. Modern science has allowed us to discover that human beings and chimpanzees are closer than we thought -- our genes 9 are more than 95% similar!

 

       Because chimpanzees and other great apes are so close to us, scientists have conducted many experiments in order to find out whether other primates can do what we do. Scientists who study animal psychology 10 have trained chimpanzees to do all kinds of things humans do, such as solving problems and even using language. While these experiments are interesting and useful, it is important to remember that they may not always tell us much about how chimpanzees think and what they are able to do. The reason is simple: what the chimpanzees are trained to do is not natural to them, nor does it make much sense to the animals. What may be of greater importance is to observe how primates live in the wild. How do they adapt to a changeable environment? Some animals have physical adaptations, such as the stripes of a zebra, which may help it hide from enemies, or the body of a camel, which helps it survive in the desert. Other animals have learnt to behave in certain ways or even use primitive 11 tools. Chimpanzees use more tools than most other animals. They use long pieces of grass to catch insects, they use stones as missiles and to crack open nuts, such as the African walnut 12, and they use leaves to collect and drink water.