Behavior that does not need to be taught are called instinctive. Instinctive behavior is also known in humans. The famous knee jerk reaction is one example. Another example is the vomiting response. Instinctive behavior needs to be triggered (e.g. by hitting the knee with a mallet), and once triggered, it cannot be stopped. Try gagging yourself and see if your brain can stop you from vomiting. It cannot. Instincts are also known as fixed action patterns, and they are hardwired into the brain in the form of neural circuits. Basically, one neuron fires after another in a fixed predetermined sequence so that muscles that are moved by those neurons will move in the correct sequence. A little known instinct found in human infants is the tendency to grab onto anything near it tightly. This instinct is also found in apes and monkeys, as they, as infants, must hold onto their mother's fur tightly while she uses both her arms to climb trees. Even though humans have evolved to be hairless, human infants still have the instinct to grab onto fur, or an adult's hair if he/she gets too close to the baby. If you have ever had your hair pulled by an infant or toddler, you know how strongly the baby can pull. Occasionally toddlers also grab onto their own hair. LOL It is pure instinct, and it does not have to be taught. Animals need to know how to mate or grab on to their mother fur instinctively because it is the difference between survival and extinction.
Since humans have evolved to have very few instincts, our brain has the extra capacity to store learned behavior than other animals. By learning, humans can cope with the environment better. There is less chance of having an instinct that is not only not needed but could be harmful. Even though the instinct to grab body fur is not needed, it has not been eliminated either because it is not harmful, and babies that still have that instinct are not more likely to die because of it.