1. Give birth to live young (as opposed to an egg, like a bird or
reptile)
2. Have hair on the skin
3. Feed their young milk, and
4. Are warm-blooded
We are also primates, which are typified by forward-facing eyes, and arms and fingers that can move in many directions.
The problem with using only these terms in describing humans is that it reduces us to the status of animals. To stretch the point, since God put in us many of the same
biological systems as He put in certain animals (eyes, tongues, lungs, heart, etc.), we are generally included in what is termed the “animal kingdom”, which is different, as an example, from plants.
However, we humans are not animals. The difference is that we have an eternal spirit and are made in God’s image. We therefore go beyond just the purely biological similarities to include MUCH more - like much higher intelligence, the appreciation of art and music, the extensive use of emotions, the ability to study, to speak,
to write, to worship, etc. We have free volition. We humans have very few instincts, while animals are pre-programmed with the instincts necessary for survival.
So, while we humans are technically and biologically mammals and primates, we are not animals. It’s important to make this distinction when using the terms. Because these terms can confuse and since they are regularly used by evolutionists to link us to the animal world, I don't use them in describing human
beings.