Counting the hairs on your head would be very difficult. Many have tried, but most people give up after losing count or getting bored! However, scientists say people have more than 100,000 hairs on their heads on average. Of course, this number is different from person to person. Some people have much more hair than others.
What causes hair loss? There are many reasons, such as stress, illness and styling. It also runs in families. Besides, many people simply lose hair as they grow older. To avoid losing hair. you should wash your hair correctly and condition (养护) your hair to help keep your hair healthy. It's also important to be gentle when brushing or combing hair.
Hair loss is not the same as daily shedding (脱落). People lose an average of 50 to 100 hairs a day. It's normal. If you are losing more hair than average, talk to the adults you trust. They can help you decide whether to ask a doctor for help.
Why do humans have hair on their heads? Most other mammals (哺乳动物) have thick fur (毛) covering their whole bodies. While humans grow small and fine (细微的) hairs on much of their skin, it's much thicker on the top of the head. Scientists say the answers come down toevolution. Humans probably evolved without fur because they have more sweat glands (汗腺) than other mammals. Humans walk upright on two legs. Therefore, the top of their heads needs protection from the sun. This is why people have more hair on their heads than on the rest of their bodies. The hair also helps keep heat in cold weather and keep a healthy body temperature.
