This is a book that will show you how everything, including animals, plants, the sun, the air, and more, is connected. In nature, every little bug or plant affects how another creature lives. Evolution, the way creatures change over time, also is very important. Evolution is complicated and hard to explain, so just know that it's affected by where a creature lives and what else lives there.

Let's go on a journey and see these connected things. Some are hot, some are cold. Some are small, some are large. But all of them have a connection. The examples were taken from Survival of the Sickest by Sharon Moalem.

Our first stop: your blood. There's a common disease called diabetes that causes a person to have too much sugar in their blood. It is an extremely awful disease, and it does a lot of damage to the body. But there might be a good reason why so many people can get it.

To understand this, we have to go back 15,000 years, when Earth started to get very cold, very fast. This time was called the Younger Dryas. What does this have to do with blood sugar? Well, sugar makes it harder for liquids, like blood, to freeze. Some scientists think that people with diabetes in the Younger Dryas were more likely to survive, helping diabetes survive to this day. Who would've thought a dangerous disease helped us survive?

Now we move from the icy cold to sunny heat. You already know that it's important to go outside and get sunlight. One reason this is important is because of a chemical called Vitamin D. When you're in the sun, your skin starts making Vitamin D, which you need in basically all of your body. But the sun isn't perfect.

While it's important for you to get exercise outside, staying too long will hurt another important chemical, folate. Too much sun hurts the folate in your skin, and can lead to many different problems. So you can't stay out too long and harm your skin, but if you're not out enough you don't get Vitamin D. All these chemicals are related to your body and the world around it, with nothing being isolated.