It makes sense if you think in terms of recycling. A recent Nature Molecular Cell Biology paper prompts this reflection:
Cells are environmentally “green” — they are experts at recycling. Why let all those amino acids, sugars, and other building blocks go to waste? While living, the cell keeps its lysosomes and proteasomes (molecular machines that recycle substrates) busy dismantling spent proteins and sending the components to recycling centers. Eventually, the whole cell’s work is done, or worse, has become infected and needs to commit hara-kiri. There’s an app for that. Apoptosis, programmed cell death, is a suite of tools and operations. Cells contain self-destruction kits, like spies with poison pills for use if captured. The poison pills consist primarily of the caspase family of proteins. Numbered caspase-1 through -14, these enzymes cut through (“cleave”) molecules like buzz saws. They are stored in an inactivated form for safety, like chain saws with covers and batteries removed. There’s more to the kit than that, though. …
Numerous actors come onto the stage when the apoptosis signal is triggered. In a sequence of steps, caspase-3 activates two other enzymes that create “find-me” signals that are sent out to attract wandering macrophages. A macrophage (a type of white blood cell in the immune system) knows how to engulf a target, which might be a pathogenic invader or a dying cell. The find-me signal is more than a beacon. It can even modify the macrophage’s behavior depending on the situation.Evolution News, “In Cell Death, a Stunning Display of Intelligent Design” at Evolution News and Science Today
According to Darwinians, it all arose randomly, just like the highway systems of North America.