Assalam U Allakum
In science we say that some animals have more than one heart but in Surah AL Ahzab it is that Allah had not made more than one heart for a single person

Assalam U Allakum

4. Allah has not put for any man two hearts inside his body.

Human beings are what is meant, not animals.

And few animals have two hearts, while I may be wrong, biology was many years ago, was it not just a few invertebrates like squid that have two hearts.

Man has one heart, it has two chambers but only one heart.