Life is incredibly complicated. Every question that the scientific world answers raises countless more. However this complexity comes at a cost: the cost of fragility.
Once again, we have to address biology from the basis of universal law. Whenever anything grows complicated, it becomes harder to maintain. Consider construction, for example:
Imagine a brick house being built. Individually, a brick is very strong and can handle most things you can throw at it. However, once a construction team comes in and builds a house (inputting energy to increase complexity), the whole becomes much more fragile. The removal of a few critical structural components can result in the entire building collapsing.
Similarly, all forms of life face this challenge. Unfortunately, this challenge is many, many times more difficult for us than a brick house.