A picture of a fish with human teeth found in Russia, which made the rounds on the internet last week, has left many people with a number of questions.
According to Cornell University evolutionary biologist William Benis, from an evolutionary point of view, it could actually be the case that it's the other way round, and human's are the ones who have fish teeth.
"Fishes with specialized dentitions long predate the origin of humans," he said.
Scientists are also familiar with a fish, called the Helicoprion, which swam the oceans around 270 million years ago and had spiky teeth in its lower jaw, just like a buzzsaw.
According to Yahoo! U.K., the Russian fisherman who caught the fish actually caught a pacu, which is a relative of the piranha.
Pacus, which are freshwater fish native to South America, have a square jaw with human looking teeth which are pointed and sharp and used for eating their meaty meals.
Even though pacus are usually found in South American waters they have been discovered further afield as well. Biologists suggest that some pacu owners dump the fish into lakes when they grow too large for aquariums.
Dr. Benis added that there are also other species of fish which have teeth that resemble those of humans. Some fish even have teeth which closely resemble human incisors, and many believe that fish's teeth over time have evolved to help them process the various vertebrates, invertebrates, and plants they eat.
Evolutionary biologist Brian Sidlauskas of Oregon State University said about pacus, "This doesn't mean that pacus have human teeth, or that humans have pacu teeth. We're just so familiar with our own morphology. That we say, 'Oh, that looks so much like us'."
Nevertheless, the discovery of the fish with human teeth in Russia was certainly shocking for the fisherman who found it, as pacus in the northern waters of Russia are virtually unheard of.