Human beings are the only animals which can draw straight lines. Human skin is completely replaced about 1,000 times during a person’s lifetime. A person who smokes a pack of cigarettes a day is doing the equivalent of drinking half a cup of tar a year. Women blink about two times less often than men. The structure of the human body contains only four minerals: apatite, aragonite, calcite, and crystobalite. A passionate kiss causes the same chemical reactions in the brain that skydiving and firing a gun do. Men are officially classified as dwarves if their height is below 1.3 m, whereas for women the measure is 1.2 m. Fingernails grow about four times faster than your toenails. People with blue eyes are more sensitive to pain than others. 100,000 chemical reactions occur in the human brain every second. Everyone has dimples on their lower back, but on some people they are more pronounced than on others. They appear where the pelvis joins with the sacrum, so their appearance makes sense. If one identical twins lacks a certain tooth, the other twin will not have that tooth either. The surface area of the human lungs is approximately equal to the area of a tennis court. During a person’s lifetime, they spend about 2 weeks kissing. The facial hair of a blonde-haired man grows faster than that of a man with dark hair. Leukocytes in the human body live for two to four days, and erythrocytes for three to four months. The strongest muscle in the human body is the tongue. The human heart is approximately equal in size to that of a person’s fist. An adult’s heart weights 220-260 grams. At birth, there are 14 billion cells in the human brain. This number does not increase throughout a person’s lifetime. After 25 years, the number of cells falls by 100,000 every day. About 70 cells die in the minute it takes you to read a page in a book. After 40 years, the decline of the brain accelerates sharply, and after 50 years neurons (that is, nerve cells) shrink and the brain gets smaller. At birth, a child’s body is made up of around 300 bones. But an adult has just 206. During a person’s lifetime, the small intestine is about 2.5 meters. After they die, the muscles in the walls of their intestine relax, and it’s length increases to 6 meters. Your right lung can take in more air than your left. An adult person performs around 23,000 inhalations and exhalations a day. The smallest cells in a man’s body are sperm cells. There are about 40,000 bacteria in the human mouth. Each of us has around 2,000 taste buds. The human eye can distinguish 10 million different colors. The chemical compound in the body which causes feelings of ecstasy (phenylethylamine) is also contained in chocolate. A person burns more calories when they are asleep than when they watch TV. Children grow faster in the spring. Every year more than 2 million left-handed people die because of mistakes they make when using machines designed for right-handed people. It turns out that one man in every three hundred is capable of satisfying themselves orally. By the age of 60 most people lose half of their taste buds. The rate at which a person’s hair grows doubles during an airplane flight. One percent of people can see infra-red light and 1% can see ultra violet radiation. If you were locked in a completely sealed room, you would not die due to a lack of air, but from carbon dioxide poisoning. Statistically, only one person out of two billion reaches the age of 116 years old. On average, a person says 4,800 words in 24 hours. The retinas inside the eye cover about 650 square mm and contain 137 million light-sensitive cells: 130 million are for black and white vision and 7 million are for helping you see in color. In the morning, a person is about 8 millimeters taller than in the evening. The muscles which help your eyes to focus complete around 100,000 movements a day. In order to make your leg muscles do the same amount of movements, you would need to walk 80 kilometers. A cough amounts to an explosive charge of air which moves at speeds up to 60 miles per hour. It is impossible to sneeze with your eyes open. Ingrown toenails are hereditary. A person would die quicker from a total lack of sleep than from hunger. Death would occur after ten days without sleep, whereas from hunger it would take several weeks. The average life expectancy is 2,475,576,000 seconds. During this time we pronounce, on average, around 123,205,750 words and have sex 4,239 times. hair comb