
What do all mammals have in common? A good question for anyone curious about the world around them and the animals that live in it. When you think of mammals a few animals should come to mind. Lions, tigers, bears, and even you are all considered mammals. What makes us considered to be mammals though? We all share a few key characteristics that make us mammals.
1. Mammals Have Hair and Fur.

All mammals (excluding some like dolphins) have some sort of hair or fur covering their bodies. This is an evolutionary adaption to protect our skin from the elements. For some animals, the fur that grows from their bodies provides camouflage from predators depending on the environment in which they live.
2. Mammals Are Warm-Blooded.
We are all warm-blooded. That means that our bodies regulate our temperatures for us. No matter if it’s freezing cold or scorching hot, a mammal’s body will always attempt to regulate its temperature to stay generally the same. This is why we shiver when we are cold. It’s our brain’s way of stimulating the body’s muscles to move and generate warmth.
3. Mammals Have Large, Complex Brains.
Unlike other animals, mammals generally have larger and more complex brains. We did not evolve this way for the reason you may think. It wasn’t based on a need to inherently be smarter, but for more basic needs such as a better sense of smell and hearing. It makes sense from a survival standpoint. Being able to smell prey or even predators better would be a trait to survive through natural selection and evolution.
4. Mammals Are Born Alive
In the animal world birthing usually happens one of two ways. The mother lays an egg and nurtures it until it is ready to hatch. This is the method for most non-mammal species. Mammals birth their young fully alive. Usually 9-12 months after impregnation, mammals will birth their babies fully developed.
5. Mammals Have Mammary Glands
Have you ever wondered where the word “Mammal” comes from? Well, its because we all have mammary glands located in our nipples. You can just think of mammary glands as oversized sweat glands. Males and females both have them however, in males they are not fully developed. This is why female mammals are tasked with the feeding of young. With their fully developed glands, they can produce milk to feed their newborns until they can fend for themselves.
6. Mammals Have a Single-Boned Lower Jaw
All mammals have a single boned lower jaw called the dentary. This bone holds all of the teeth in your lower jaw and, attaches directly to your skull. Other animals have many different bones holding their lower jaw together. This differentiates mammals because it endows them with a powerful bite. This bite can be used to cut through meaty prey or gnaw through vegetables.
7. Mammals have Three Bones in the Middle of the Ear.
The incus, the malleus, and the stapes are the three bones that all mammals have in their inner ear. Also known as the hammer, the anvil, and the stirrup, these bones are responsible for the mammal’s ability to hear. They vibrate together and transmit sound from the eardrum, translating the vibrations into signals that the brain can then process.
So in conclusion, what do all mammals have in common? They have fur and hair covering their skin to protect them from the elements and help hide them from predators. They are warm-blooded meaning that they can regulate their own temperature. No matter if it’s hot or cold in their environment, mammals generally hold the same body temperature.
They have evolved with larger more complex brains to aid in enhancing their basic sensory needs such as sight and hearing.
Mammals birth their babies alive and fully developed. They also have mammary glands that the females use to feed their young by secreting milk from them. They have a single boned lower jaw which gives them a powerful biting force that they can use for tearing through meaty prey and gnawing on vegetation. They have three bones in the middle of their ear called the incus, the malleus, and the stapes.
If you are ever curious about what makes a mammal special, just take a look in the mirror. All the traits that make you human are also what makes mammals, mammals.