system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we have 2 of some organs but only 1 of others?
gpt
Because sometimes we only need the one (reproductive organs, mouths, anuses), and sometimes we need two for redundancy (kidneys, lungs, arms)

As organisms evolved, the most advantageous adaptations survived. So, if only having one kidney or having four stomachs was better, we would have likely eventually evolved to have them.