Ask Dr. Universe

Episode 3: Knuckle-Walking Apes, Yawning Tears, Best Exercises, A Pandemic Mystery

November 24, 2020 Washington State University
Ask Dr. Universe
Episode 3: Knuckle-Walking Apes, Yawning Tears, Best Exercises, A Pandemic Mystery
Show Notes Transcript Chapter Markers

Have you ever wondered why apes walk on their knuckles? Why we make tears when we yawn? Why and how exercise helps our bodies? What's the best exercise? (5:17) How the COVID-19 pandemic started?

On this episode, we’ll dig into these great kid science questions with help from researchers at Washington State University. Thanks to Parker for helping read the questions on this episode. If you would like to help read questions on a future episode send an e-mail to

Thanks to WSU researchers Nanda Grow, Karin Biggs, Chris Connolly, and Michael Letko for helping with the science.

If you'd like to submit a question of your own for a chance to be featured on the podcast visit

Dr. Universe  0:00  

Hello young scientists. I'm Dr. Universe and if you're anything like me, you've got lots of big questions about our world. On this episode, we'll talk with researchers at Washington State University about why apes walk on their knuckles. Why we get tears when we yawn? How exercise helps the body and investigate a question about what started the Covid-19 pandemic. Then stick around for another question from one of our listeners about how leaves know when to change colors. A big thanks to our guest narrator Parker for helping read the questions on this episode. If you'd like to help read questions on a future episode, send me an email at Let's get started.

Narrator, Parker  0:47  

Hi, I'm Parker. This question comes from Sam age 10 in Benton, Arkansas. Dr. Universe, Why do apes walk on their knuckles?


Dr. Universe  0:59  

I took your question to a primatologist at Washington State University.


Nanda Grow  1:04  

I'm Dr. Grow I am an anthropologist and wildlife biologist. So what that means is I study animals in order to try to understand humans and I focus on primates and apes are primates that include knuckle walkers like chimpanzees and gorillas. 


Dr. Universe: Why do they walk this way? 


Nanda Grow: Gorillas and chimpanzees, they both do the knuckle walking, but they do different kinds type a knuckle walking that chimpanzees do. It's kind of like their wrist is more extended out. Whereas with gorillas it's more like a fist almost. It's primarily for stability, it's so that they're not bearing too much weight in their joints. 


Dr. Universe  1:43  

Can you guess how much a male gorilla weighs young scientists? If you guessed around 400 pounds, you are correct. That's a lot of weight to carry around.


Nanda Grow  1:59  

The knuckles, if they're bearing a lot of the weight, that just spreads out the load more.


Dr. Universe  2:03  

Where an animal lives, whether it's up in the trees or down on the ground, also plays a role and the way that it moves around. Not all apes use their knuckles to walk. Gibbons don't knuckle walk, but they do have really long arms that are great for climbing trees. One animal that also likes spending time in trees is the pygmy tarsier. That's about the size of a guinea pig. You studied pygmy tarsiers? Can you tell us how they move around?


Nanda Grow  2:29  

It's like the opposite. Basically, instead of having long arms, they have shorter arms and they have really long legs. So that helps them to leap. And when they actually land on a tree. They cling to vertical substrates like tree trunks rather than branches.


Dr. Universe  2:45  

These little animals can jump almost 10 times their body length. Just imagine how far you could jump with legs like a pygmy tarsier. Whether primates are swinging, jumping, skipping, knuckle walking or walking upright. every species knows the right way to get from place to place. Let's swing on over to the next question.


Parker  3:06  

Here's a question that comes all the way from Australia. Ella, age eight asks, Why do we get tears your eyes when we young?


Dr. Universe  3:16  

You're right. A lot of people get tears when they yawn. When you yawn, you actually use a lot of muscles in your face. Maybe you can feel the stretch in your jaw, cheeks and eyes. My friend who teaches anatomy at Washington State University was happy to help with your question.


Karin Biggs  3:33  

My name is Karen Biggs and I have a PhD in zoology. But right now, I like to focus on teaching and I love to teach people about the way their bodies work, and about why we should care about how our bodies work.


Dr. Universe  3:52  

Can you tell us a bit about tears?


Karin Biggs  3:55  

Tears are made all the time they are responsible for keeping our eyes moist and helping us see and keeping our eyes healthy.


Dr. Universe  4:02  

How exactly do we make them?


Karin Biggs  4:04  

Yeah, so I actually have a little bit of visualization I wanted to show you if that's possible, I'll share my screen. Cool. 


Unknown Speaker  4:12  

Okay, young scientists, we're looking at a computer model of the human body with all its amazing structures, including the eye. Almond shaped structures called tear glands or lacrimal glands produce tears and they're located by the eyelid. 


Karin Biggs: On the inside corner of the eye are two tiny tubes, one tube here in one tube here right below it. Those are the ways the tears, exit our eyes. 


Dr. Universe: When we yawn our muscles can put a lot of pressure on this little plumbing system.


Karin Biggs  4:45  

We have 43 different muscles in our face to let our face do so many wonderful thing when we young you're contracting all the muscles in our face. And so we're just squeezing the tears out of the glands and out of those tubes because we've seen squeezed all of our face at once. 


Dr. Universe  5:03  

Tears are a big part of the human experience. But did you know other animals like cats, and elephants can make tears to tears are mostly water with some other ingredients that help keep our eyes in good shape? Speaking of keeping the body in good shape, our next question is all about exercise. Laila five and a half asks, Why and how does exercise help our bodies? And she would also like to know, what is the best exercise for our bodies? When I got this question, I called up my friend, Associate Professor Chris Connolly. Can you tell us a bit about yourself?


Chris Connolly  5:39  

I am an exercise physiologist. And so I study how the body works. When we exercise when you exercise, there are a lot of really wonderful things that happen in your body.


Dr. Universe  5:52  

Can you tell us about some of them?


Chris Connolly  5:54  

You have a lot of systems in your body and a lot of muscles, and a lot of organs, and all of those get good exercise when you move your body. One example, there's lots of examples we can talk about, but one example would be your heart. And it pumps blood and oxygen to all of your muscles to everywhere in your body and your body needs blood and oxygen. Okay, and we need oxygen to produce not all of our energy, but most of it.


Dr. Universe  6:29  

I think it's time for a stretch break. Can you stretch your arms out like a starfish, hop like a frog or walk like a crab? Sometimes I notice that exercise, even stretching helps me relax.


Chris Connolly  6:45  

Yes, it's really good for your mind. That's another thing that gets lost sometimes is exercise and physical activity is so important for your mind for being able to think clearly, improving memory, improving creativity.


Dr. Universe  7:02  

Exercise helps us in a lot of ways. But what exactly is the best exercise for us?


Chris Connolly  7:08  

What's the best exercise, it's what you're going to do consistently, and make a habit in your life.


Dr. Universe  7:15  

Humans have different abilities and interests. So the best exercise will look a little different for each person. Next time you do your favorite exercises, think about all the wonderful things you're doing for your body and all the wonderful things your body does for you. Here's our next question.


Parker  7:31  

Coleen age 10 in Louisa, Virginia asks, Dear Dr. Universe, I heard a little bit about how COVID-19 started, but I don't know much about it. What happened?


Dr. Universe  7:44  

It turns out scientists around the world are investigating this very question. I asked my friend, biologists Michael Letko all about it.


Michael Letko  7:53  

We know a fair amount about coronaviruses in general, but we don't know them a whole lot about the specifics on this one yet. But basically, we can assume that it starts in one animal and gets to us somehow. How is the is the challenging part. 


Dr. Universe

There are a lot of different kinds of coronaviruses what are some animals that carry these kind of viruses? 


Michael Letko: People look at a lot of bats. So we happen to know that there are a lot of coronaviruses in bats. But you know, the more we look elsewhere, we also find them in a lot of places, not just bats, rodents, and there's even like a seal one now and a whale Coronavirus.


Dr. Universe  8:35  

When we first learned about the latest Coronavirus that causes Covid-19 virus hunters set out to find the source. Can you tell us more about these virus hunters? 


Michael Letko  8:46  

These are scientists that go out into the field. And they capture bats and they capture wildlife and they take their blood and they swab them with tips and they look for viruses.


Dr. Universe  8:58  

When scientists look at connections between different animal species, they can start to learn more about how viruses infect humans. But it isn't always an easy task. Is it?


Michael Letko  9:10  

The chances of you ever finding a bat that has this exact virus in it, it is just a needle in the haystack.


Dr. Universe  9:18  

We may not all be scientists but we can all do our part. When you wear a proper face mask. Practice social distancing, and wash your hands you help prevent the virus from spreading to you and those around you. We can all do our part to stay safe and healthy. 


Our next question is from podcast listener Emmi, age 10 in Edmonds, Washington. How do leaves know when to change color? It's all about something called chlorophyll, Emmi. When leaves are green, they have a pigment called chlorophyll. Chlorophyll is not just important for color. Plants use chlorophyll to collect energy from the sun to make their own food. As the days get shorter and there's less sunlight, it sends a signal to the treat slow down growth and start to store up some of the energy they made earlier in the year. This means photosynthesis slows down and they don't need as much chlorophyll to make food. Photosynthesis slows and the chlorophyll inside the leaves breaks down. We see less green before the leaves fall off. 


That's all for this episode friends. Thanks again to Parker for helping read the questions, to everyone who submitted a question and to the researchers at Washington State University who helped with the science. And thanks to you for listening. You make this podcast possible. You can send in a science question of your own Who knows where your questions will take us next! 



Why do apes walk on their knuckles?
Why do we get tears when we yawn?
How and why does exercise help our bodies?
What started the COVID-19 pandemic?
How do leaves know when it's time to change color?