How about the fact that we have to eat and breathe through the same hole, with the result being that we can easily choke to death.
You'll understand the importance of the hole "mucus"
How do the lungs protect themselves?
The lungs have several ways of protecting themselves from irritants. First, the nose acts as a filter when breathing in, preventing large particles of pollutants from entering the lungs. If an irritant does enter the lung, it will get stuck in a thin layer of mucus (also called sputum or phlegm) that lines the inside of the breathing tubes. An average of 3 ounces of mucus are secreted onto the lining of these breathing tubes every day.
This mucus is "swept up" toward the mouth by little hairs called cilia that line the breathing tubes. Cilia move mucus from the lungs upward toward the throat to the epiglottis.
The epiglottis is the gate, which opens allowing the mucus to be swallowed. This occurs without us even thinking about it. Spitting up sputum is not "normal" and does not occur unless the individual has chronic bronchitis or there is an infection, such as a chest cold, pneumonia or an exacerbation of chronic obstructive pulmonary disease (COPD).
Reference :
Anatomy and Function of the Normal Lung
OMG,how complex is our body and you are fetching for a silly excuses to prove it to happen without an intelligent entity.