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Sharks have long been shrouded in mystery. The origin of the term 'shark' remains uncertain, with some suggesting it may stem from the Mayan word xok. This aura of the unknown, coupled with their ancient existence spanning 400 million years, makes these deep-sea inhabitants both fascinating and, at times, fear-inducing. This sense of intrigue has given rise to numerous myths and misconceptions about sharks. Let’s dive into six of the most common ones.
1. Sharks prey on humans.
The portrayal of sharks as human predators has been fueled by negative stereotypes, long before Steven Spielberg’s iconic film Jaws instilled a fear of the ocean. In reality, sharks do not actively hunt humans. Most attacks occur when a shark mistakes a person for its natural prey, such as a seal. Often, these incidents involve 'exploratory bites,' where the shark is simply investigating whether the object is edible. While shark attacks are rare, certain species do pose a higher risk.
Out of the hundreds of shark species identified, only around twelve are deemed dangerous—such as the great white, tiger shark, and bull shark—and account for the majority of human encounters. The United States leads in recorded attacks, with 1,022 incidents documented between 1670 and 2012, as per the International Shark Attack File. Australia, while second in total attacks, has the highest number of fatalities, with 144 reported by 2012.
The Global Shark Attack File (GSAF), a resource aimed at ‘offering current and historical insights into shark-human interactions,’ categorizes shark attacks into five distinct groups. The most frequent are ‘Provoked’ attacks, where ‘the shark is speared, hooked, or otherwise provoked by humans,’ and ‘Unprovoked’ attacks, which occur when ‘a shark views a human as a threat or competitor for food.’
2. Sharks may not actively hunt humans, but they are all ruthless predators.
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With over 400 species, sharks are incredibly diverse, making it impossible to generalize their behavior. However, public perception often focuses on species like the great white or hammerhead, driven by fear and fascination, perpetuating the myth that all sharks are aggressive hunters. While these species, along with others like the blue shark and mako shark, are apex predators dominating the food chain, many shark species defy the stereotype of being purely predatory.
Consider the dwarf lanternshark, for example. This tiny creature, inhabiting the waters near Venezuela and Colombia, is arguably the smallest shark globally, measuring up to 21 centimeters—small enough to fit in your hand. It poses so little danger that fishermen often release them if caught, deeming them too insignificant. On the other end of the scale, the whale shark (pictured above)—the largest fish and shark species—can grow up to 40 feet or more. As a migratory filter feeder, it primarily consumes plankton. Despite being carnivorous, these gentle giants, comparable in size to a school bus, are so docile that they occasionally let swimmers cling to their dorsal fins.
3. Sharks will die if they stop moving.
Contrary to popular belief, most sharks do not need to swim continuously to survive. Many species utilize a method known as “buccal pumping,” which involves using their cheek muscles to draw water into their mouths and over their gills, allowing them to alternate between activity and rest.
However, around two dozen species—such as the great white, whale shark, and mako shark—are classified as “obligate ram ventilators.” For these sharks, constant movement is crucial for survival. Instead of relying on buccal pumping, they must keep swimming to force water through their open mouths and over their gills to avoid suffocation. While it’s easier for these species to remain in motion, they can briefly pause to rest before resuming their journey.
4. Sharks possess unlimited rows of teeth.
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Sharks aren’t born with an infinite supply of teeth. Instead, their sharp, serrated teeth regenerate as necessary throughout their lives.
Unlike human teeth, which are rooted in sockets and replaced only once during childhood, a shark’s teeth are connected by soft tissue to the jaw’s outer layer, making them prone to falling out when damaged or worn. Their teeth are organized in sequential rows, and when one is lost, the next tooth shifts forward to replace it, functioning like a rotating dental conveyor belt. Some sharks can have up to eight rows of teeth simultaneously, and they can grow a new tooth in as little as 24 hours. With an average lifespan of 20 to 30 years, a shark may go through thousands of teeth. For example, the spiny dogfish shark, which can live up to 100 years, likely uses an extraordinary number of teeth in its lifetime.
5. Sharks are unintelligent creatures with tiny brains.
This misconception may stem from species like the tiger shark, which appear mindless due to their tendency to eat almost anything they encounter. However, sharks possess highly developed brains, making them complex and intelligent animals.
The brain of a mature great white shark spans approximately 2 feet and is structured as a Y-shaped chain of millions of neurons, divided into hind-, mid-, and fore-brain sections (unlike the compact, spherical human brain). Nearly two-thirds of a shark’s brain is dedicated to its sense of smell, underscoring the critical role scent plays in its survival. This large olfactory region enables sharks to detect prey, navigate territories, and locate mates—abilities vital to their existence.
Regardless of perspective, sharks are highly intelligent beings with a keen awareness of their surroundings. Their cognitive abilities are so advanced that they can even be trained!
6. Sharks are immune to cancer.
You’ve likely encountered dubious claims from snake-oil peddlers, but have you heard of shark cartilage sellers? Some alternative health stores promote shark cartilage as a cancer prevention remedy, citing anecdotal evidence that sharks don’t develop cancer. There are even books claiming to offer cures.
However, this is a myth—its origins are explained here. In reality, numerous cases of both benign and malignant tumors in sharks have been documented in scientific and medical literature. Researchers like John C. Harshbarger and Gary Ostrander debunked this myth by presenting 40 documented cases of cancerous tumors in sharks at the American Association of Cancer Research in June 2000.
This misconception poses a dual threat: not only does it mislead cancer patients—since shark cartilage has no proven cancer-curing properties—but it also endangers sharks. The demand for shark cartilage has fueled a multi-million dollar industry, leading to a drastic decline in shark populations. "In the last decade, North American shark populations have plummeted by up to 80 percent, with cartilage companies harvesting as many as 200,000 sharks monthly in US waters to produce their products," notes Christie Wilcox in a 2011 Scientific American article.
The truth is clear: Sharks do develop cancer. Anyone claiming otherwise is either misinformed or has a product to sell.
