An animal that was called proof of God's sense of humor was found to have a complete lack of stomach

In the movie Dogma (1999), there is a phrase at the beginning: "Even God has a sense of humor. Just look at the platypus". This cute animal does look funny, but the biggest oddity is that it lacks an important digestive organ.

The platypus does not have and will never have a stomach, writes IFL. Nature also deprived the animal of the genes associated with the functioning of this organ.

This was an interesting addition to what scientists knew about vertebrate evolution. "All of these genes are highly conserved in vertebrates, reflecting a unique pattern of platypus genome evolution that has not been previously observed in the genomes of other mammals," the authors write.

In fact, the loss of an organ does not always mean the loss of the genes associated with that organ. For example, the cave form of the Mexican tetra has no eyes, but it still has the genes for their development - they were just muted.

However, in many animals that had lost their stomachs, the team of scientists found that the genes associated with it had actually been deleted.

The stomach is an ancient element in vertebrate history, believed to have first appeared in the form of gastric glands about 450 million years ago.

The stomach is absent not only in the platypus, but also in the echidna, as well as in 20-27% of the group that includes the vast majority of fish species.

Filipe Castro and his colleagues compared the genomes of 14 vertebrate species, including humans, mice, and zebras, to test their hypothesis that the loss of the stomach in the course of evolution correlates with the loss of key stomach genes.

In doing so, they found that all animals without stomachs lacked genes encoding the gastric proton pump; this is an enzyme that acidifies stomach contents and is often targeted to relieve acid reflux symptoms in humans.

The genes encoding a class of enzymes secreted by stomach cells that help break down proteins known as pepsinogens were also missing - with the exception of pufferfish and platypus. They have only one of the genes, but it has no stomach-related function.

Why did they lose them? The researchers speculate that it could be due to changes in diet or environment that meant they no longer had a need for these genes, and so they gradually disappeared in the course of evolution.

Regardless of why stomachless animals lost this organ, since the corresponding genes have been lost, it is unlikely that they will ever get their stomachs back. This is explained by a rule of evolutionary biology known as Dollo's law, which views evolution as a one-way street: if a complex trait is lost, it cannot be restored.

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