system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Instincts, how they work and how a baby knows to suck on its mothers nipple to get milk

Title says it all. I get that all animals have instincts, but HOW? How do they know to do the things they do? Where are the instincts stored? Do they evolve over time?
gpt
When your potential ancestors didn't do this, they died.

The one thing your ancestors all have in common, right back to the first molecule of organic matter, is that they survived long enough to produce offspring.