Why did early humans leave Africa? They were probably forced out by climate change, but they could have left because of their rising intelligence. Let’s look at the evidence for why paleontologists believe humans developed in Africa and then look at why they left. Humans probably separated from the common ancestor we share with other […]
#492 Why did early humans leave Africa? Read More »
Do any other animals cry? Yes, but only to lubricate their eyes. We have three types of tears. We have tears that lubricate and clean our eyes. These are called basal tears and they are created automatically. Every time you blink, the basal tears are spread across the eye and keep it wet and clear
#491 Do any other animals cry? Read More »
How do parrots talk? They can imitate human speech by passing air across the opening of their trachea using an organ called a syrinx. Parrots don’t talk in the wild. And when we say “talk”, they mimic human speech without necessarily understanding what they are saying. Some parrots have been taught to learn the names
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Does blood volume decrease if a limb is amputated? Yes. The kidneys will monitor the blood pressure and try to lower the volume of blood if it is too high. People of the same weight and height don’t necessarily have the same amount of blood and the amount of blood a person has will vary
#483 Does blood volume decrease if a limb is amputated? Read More »
Why can’t all animals be domesticated? There are six criteria needed for an animal to be domesticable. The first animals were domesticated about 15,000 years ago. Early people were hunter-gatherers, but they transitioned to agriculture about 10,000 years ago and most animals we use today were domesticated after that. The first animals to be domesticated
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Why do ostriches have two kneecaps? It (possibly) helps them to run faster. What does a kneecap do? The knee is basically a lever and the kneecap is the pivot point. In humans, the knee is the joint between the femur (thighbone) and the tibia (shinbone). The muscle on the front of the thigh bone
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Why is hypothermia dangerous? It is dangerous because it is a fatal condition. Hypothermia is often confused with hyperthermia. Hypothermia is when the human body temperature drops below 35 °C and hyperthermia is when the body temperature is above 37.5 °C. “Hypo” comes from Greek and means “under”. “Hyper” also comes from Greek and means
#476 Why is hypothermia dangerous? Read More »
How does aspirin work? Aspirin works by stopping an enzyme called cyclooxygenase. When our tissue or organs are damaged or infected, they produce prostaglandins. These are fatty acids that act like hormones. Prostaglandins do many different jobs in the body. They are similar to hormones but they are not hormones. Hormones are produced in glands,
#475 How does aspirin work? Read More »
What is cotton? Cotton is a fiber that grows around the seeds of the cotton plant. About 27 million tons of cotton is produced every year. India is the largest producer, with 6.1 million tons, and it is followed by China, the USA, Brazil, and Pakistan, in that order. A standard t-shirt requires approximately 226
#468 What is cotton? Read More »
What causes pins and needles? Pins and needles are caused because the flow of blood to your nerves is restored. Pins and needles are really called paresthesia. The word comes from the Greek para, which means “abnormal” and aesthesia, which means “sensation”. They come after one of your limbs has fallen asleep, which is actually
#458 What causes pins and needles? Read More »
