Why evolutionary biology suggests that humans are actually fish

Science · Published 7 October 2026 Swipe more like this →

In short: We often view the tree of life as a series of distinct, separate branches. However, modern evolutionary context reveals a much more interconnected reality. If you trace our lineage far enough back, the distinction between mammals and fish begins to blur, making a startling claim: humans are, in a very real sense, fish.

The way we categorize life is constantly shifting as new genetic and fossil evidence emerges. In the past, biology textbooks often taught that humans and great apes—such as chimpanzees, gorillas, and orangutans—belonged to separate groups that diverged from a common ancestor. We now know this is incorrect. Genetic discoveries have proven that chimpanzees are our closest living relatives, placing us firmly within the same lineage. This shift in understanding is driven by a combination of both fossil and genetic discoveries. This new evidence has moved the Pongidae group, which once contained the great apes, into a revised evolutionary structure.

This taxonomic fluidity extends beyond primates. Just as scientists now recognize birds as descendants of, and effectively, dinosaurs, our own classification is subject to the same evolutionary logic. The debate often centers on nomenclature. For instance, anthropologist John Hawks has argued that calling humans 'apes' is a 'canard'—a misleading term used to diminish human self-importance. He suggests using more technical terms like hominoids or hominids to avoid the vernacular baggage of the word 'ape'. This phenomenon mirrors how the term dinosaur has evolved since Richard Owen first coined it in 1842. Just as the public now accepts that birds are dinosaur descendants, we must accept our own complex lineage.

However, evolutionary biologists like Brian Switek argue that these labels depend entirely on the level of specificity required. When looking at the broader evolutionary context, the boundaries between classes of animals become much harder to define. If we follow the branches of the tree of life back through the stages of tetrapods, amniotes, and synapsids, we eventually reach a point where the distinction disappears. In this deep-time perspective, a human is simultaneously a mammal, a primate, and a fish. By tracing these ancestral connections, one can argue that a human is also a monkey, a therapsid, and an amniote. We are simply a highly specialized, intelligent version of an ape.

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