Dear Georgia,
Imagine you’re riding in the car on a very hot day, when you look out the window and see a shimmering puddle of water up ahead. As you get closer, you find there’s not really anything there. It’s a mirage. » More …
-Sarah, Tacoma, Wash.
Dear Sarah,
At this very moment, several quarts of blood are circulating through your body at nearly 4 mph. But as you’ve pointed out, not everyone’s blood is the same.
Your question made me wonder exactly what we mean when we talk about blood types. I decided to ask my friend Amber Fyfe-Johnson, a researcher at Washington State University who studies cardiovascular diseases–diseases of the blood vessels– in kids.
Believe it or not, she said, there are more than 20 different blood groups. We’ll stick to the main one for now: ABO. There are 4 different types in this group: A, B, O, and AB.
You have trillions of blood cells. Each blood type refers to a specific marker on a red blood cell. It’s kind of like a little flag.
In the early 1900s, an Austrian doctor named Karl Landsteiner discovered three of the little flags. Today, we call these three flags A, B, and O.
These little markers make blood types compatible with each other. If a person with Type A blood is given Type B blood, his or her body sees the Type B surface flag as foreign and rejects it.
Meanwhile, Type O doesn’t have those surface markers. There is nothing on the surface of the red blood cell to reject. Type O blood can be transferred to pretty much anyone who needs it.
Fyfe-Johnson explained that the blood types we have today evolved a very long time ago. Type A is the most ancient blood type and has been found in hominids – or pre-humans. Scientists can use DNA from some blood cells found in fossils to help figure this out. Type O probably originated next, about 5 million years ago. Scientists are still trying to pinpoint when exactly each blood type evolved.
As is often the case, there are a few ways to think about the answer to your question.
One way to think about it is that our parents pass genetic information about our blood types down to us. It’s part of our DNA. Sometimes there’s a change, or mutation, in DNA.
“These different blood types evolved as a result of genetic mutations, but what caused certain blood types to be more successful is likely exposure to infectious diseases or other environmental pressures,” Fyfe-Johnson said.
The kinds of blood types that survive infections are often the ones that outlive the others.
For example, cells that are infected with a disease called malaria don’t stick to Type O or Type B red blood cells. Those with Type A blood who are infected with malaria are more likely to have clumps of cells form that can be harmful. Especially when they form in places like the brain or heart.
People with Type A blood are more likely to have serious complications or die as a result of malaria, whereas people with other blood types could survive. This happens with many kinds of diseases, she said.
“The short story is that blood types probably evolved as a way to fight infectious diseases or other environmental pressures,” she said. “Blood types that survived were more likely to be successful.”
In a way, it’s all about survival of the fittest blood.
–Riley, 11, Prior Lake, MN
Dear Riley,
Humans have hair all over their bodies, including above the upper lip. Of course, not all hair is quite the same. A lot of people have very fine hairs on their faces. Others can sprout a thick beard or mustache. » More …
– Charan and Aishwarya V., 10 & 8, Rutherford, New Jersey
Dear Charan and Aishwarya,
Imagine you are playing a game of soccer and your best friend is on the opposing team. The sun is out, you are having a great time, and you score the winning goal. You’d probably feel pretty happy and so would your team. » More …
-Gianni, 10, Cayman Islands
Dear Gianni,
Our planet is home to more than seven million amazing animal species. While we have our differences, we also have something in common: We are all made up of a bunch of cells. » More …
–Norelle, Olympia, Wash
Dear Norelle,
Our bodies have many living parts, like skin, muscle, brain and bones. Blood helps keep these parts alive and healthy. The system that moves our blood around the body is sort of like a city’s postal service, said my friend Astrid Suchy-Dicey. » More …
-Keegun, 8th grade, E. Wash.
Dear Keegun,
We’ve got about three pounds of brain in our heads that help us look for answers and solve all kinds of problems. But it isn’t always easy. Sometimes an experiment doesn’t go the way I expect or I get stuck on a particularly tricky science question. » More …
– Gabby G., 11, Berlin, VT
Dear Gabby,
Our brains are pretty busy. They are constantly thinking, feeling, and sensing our world. One thing that can help some people relax is spending time with an animal friend. You might play fetch with a dog, sit with a cat, brush a horse, or even watch a goldfish zip around its bowl.
People who spend a lot of time with animals might tell you that something special seems to be going on here. But scientists are looking for evidence and want to find out for certain just what is going on. They want to know more about what happens when animals and humans spend time together.
One scientist who studies human and animal interaction is my friend Phyllis Erdman at Washington State University. After her day at work, she said, the first thing she does is go home and play with her dogs.
Everybody knows that we feel good when we are with animals, Erdman said. But we also need the science to back up the idea. She said one notion scientists test out has to do with different chemicals that are in our brains. Our body makes all kind of chemicals and some can make us feel pretty happy.
When babies and mothers bond, scientists often see the chemical oxytocin (ox-ee-toe-sin) at work in their brains. It turns out that oxytocin may be released when people spend time with animals, too.
The chemical helps us build trust and bond with each other. When it’s released in the brain, it lets you know that something, usually good, is happening. Maybe that thing is spending time with a whole bunch of kittens or puppies. The interaction can be good for the animal, too. We are social. And we like a good ear scratch or belly rub.
Erdman has actually worked with dogs and kids to study their interactions, too. She’s also worked with horses. Just brushing and taking care of the animal helped kids feel like they could let go of stressful things.
A lot of human and animal interaction scientists study behavior. But now many are becoming curious about actual changes in the brain itself. New studies are exploring images of the brain when animals and humans spend time together.
The field of human and animal interaction is growing, Erdman said. Perhaps by the time you get to college, we will have more answers to your question. Who knows, maybe you’ll even be one of the people to help us research big questions about how humans and animals can help each other out.
Sincerely,
Dr. Universe
Why do we have water in our bodies? –Angelika, 12, Cathedral City, CA
Dear Angelika,
Believe it or not, we are mostly water. Of course, you may have noticed we aren’t sloshing around and spilling everywhere. » More …
Dear Dr. Universe: How do our ears work? -Aryana, 11, Ohio
Dear Aryana,
The chirps of birds. The squeaks of mice. The barks of dogs. In a world full of different sounds, our ears take in almost everything. But it takes more than just our ears to hear. » More …