Platypuses eat without stomachs

The platypus is already a biological disaster, but its insides make even less sense: it completely lacks a stomach. When a platypus eats, the food travels down its throat and goes directly into its intestines.

In almost every vertebrate, the stomach uses acid and enzymes to break down complex proteins. The platypus simply deleted this step from its DNA millions of years ago.

Scientists found that the genes required to create stomach acid and digestive pepsin are actually missing from the platypus genome. They didn't just stop using them; they erased the blueprints.

Its diet consists of bottom-dwelling insects and shrimp, which it grinds up using hard pads in its mouth since it also has no teeth.

Because there is no acidic 'holding tank' to break down meals, the food just drifts through the digestive tract. This adaptation likely occurred because their diet is high in calcium carbonate, which would neutralize stomach acid anyway, making the organ unnecessary.

A few species of fish also lack stomachs, but the platypus is one of the only mammals to pull off this anatomical disappearing act.

This raises a weird question: why evolve an organ as useful as a stomach just to throw it away?