Why can’t humans eat certain animals? This is a fascinating question that many people ponder when considering which meats are safe and nutritious to consume. The quick answer is that some animals contain toxins or diseases that can make people sick.

However, the full explanation involves an in-depth look at animal biology, human evolution, and food safety regulations.

In this comprehensive guide, we will explore the key reasons why humans avoid eating particular animal species. We will cover biological factors like toxins and diseases, evolutionary perspectives on human diets, and legal restrictions around consuming unconventional meats.

Read on to learn everything you need to know about which animals are off limits for human consumption and why.

Toxins in Animals

Poisonous Amphibians

Many amphibians contain toxins in their skin that make them poisonous to humans and other animals. The most infamous are poison dart frogs, which get their name from indigenous people using their secretions to poison the tips of blowdarts for hunting.

While their bright colors warn predators to stay away, the toxins can be fatal if ingested. The golden poison frog contains some of the most potent toxins on Earth and just 2 micrograms can kill a human (1).

Other poisonous amphibians include the brightly colored blue poison dart frog, the strawberry poison frog, the Harlequin poison frog, and the clown frog. Even touching these frogs can cause severe illness, so it’s best to admire their beauty from a distance!

Venomous Reptiles

Venomous snakes, lizards, and spiders pose a huge danger to humans if they bite and inject their toxic venom. The inland taipan of Australia is considered the world’s most venomous snake; its neurotoxin venom can kill an adult human within 45 minutes (2).

The black mamba in Africa is also extremely deadly, along with rattlesnakes, copperheads, and cottonmouths in the Americas. Venomous lizards include the Gila monster and Mexican beaded lizard, whose bites cause excruciating pain.

And who hasn’t heard horror stories about the lethal Black Widow spider bite or being on the receiving end of a scorpion sting? It’s critical to learn how to identify these hazardous creatures and give them a very wide berth.

Toxic Fish and Invertebrates

Lurking below the water’s surface are many species loaded with toxins and venom that can harm or kill humans. The venomous blue-ringed octopus bite contains tetrodotoxin that can lead to paralysis and death within minutes (3). Stingrays can deliver an agonizing sting from the barbed tail.

Poisonous fish include pufferfish containing the deadly neurotoxin tetrodotoxin, as well as porcupinefish, ocean sunfish, and the brightly colored lionfish. Aquatic animals with venomous spines include sea urchins, crown-of-thorns starfish, and cone snails, which can fire a harpoon-like tooth into their prey.

So explore the underwater world with great caution!

Animal Toxin/Venom Effects
Golden Poison Frog Batrachotoxin Heart failure, paralysis
Inland Taipan Snake Neurotoxin Paralysis, respiratory failure
Blue-Ringed Octopus Tetrodotoxin Paralysis, respiratory failure

With education and proper precautions, we can safely observe these marvelous yet hazardous animals from a distance. After all, their unique toxins and venoms are part of their astounding biological survival strategies.

By respecting nature, we can thrive alongside even the most poisonous and venomous species on Earth.

Diseases in Animals

Animals can carry a variety of concerning diseases that can be transmitted to humans through contact or consumption. Being aware of these illnesses and taking proper precautions can help prevent potential health issues.

Prion Diseases

Prion diseases, also known as transmissible spongiform encephalopathies (TSEs), are a group of progressive neurodegenerative disorders that affect the structure of brain tissue in humans and animals. Some examples include bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, in cattle, chronic wasting disease (CWD) in deer, elk, reindeer and moose, and scrapie in sheep.

These diseases are caused by prions, misfolded proteins that trigger normal proteins in the brain to also fold abnormally. As prion proteins accumulate in the brain, tiny holes develop leading to a “spongy” appearance under a microscope.

This causes neurological symptoms like personality changes, loss of bodily functions, and death.

It’s important to note that consuming meat or other products from animals with prion diseases can potentially be fatal. For example, the human version of mad cow disease called variant Creutzfeldt-Jakob Disease (vCJD) is believed to be contracted from eating beef products contaminated with central nervous system tissue carrying mad cow disease prions.

Foodborne Illnesses

Eating undercooked or contaminated animal products is also associated with various foodborne illnesses caused by bacteria, viruses, parasites or toxins. According to the CDC, around 48 million Americans get sick from foodborne diseases each year, leading to 128,000 hospitalizations and 3,000 deaths.

Some common foodborne illnesses from animal products include:

  • Salmonella – Caused by the salmonella bacteria often found in raw or undercooked poultry, eggs, beef and seafood
  • E. coli – Various strains of the escherichia coli bacteria are found in the intestines of livestock that can contaminate meat if intestinal contents leak during slaughter
  • Listeria – The listeria bacteria can contaminate deli meats, hot dogs, dairy products made from unpasteurized milk and soft cheeses

Properly cooking meats to recommended safe internal temperatures, avoiding unpasteurized dairy products, and practicing good hygiene when handling raw animal products can help prevent many foodborne diseases.

Zoonotic Diseases

Zoonotic diseases are illnesses caused by bacteria, viruses, parasites and fungi that can spread between animals and humans. According to the CDC, 3 out of every 4 new or emerging infectious diseases in people come from animals.

Both domestic and wild animals can transmit zoonotic diseases directly through contact or indirectly via insects or contaminated food or water sources.

Some examples of concerning zoonotic diseases include:

Disease Animals Involved
Rabies Dogs, bats, raccoons, skunks, foxes
Leptospirosis Rodents, dogs
Psittacosis Birds (parrots, parakeets etc.)

Preventative measures like avoiding contact with wild animals, properly containing and vaccinating domestic pets, and wearing protective equipment when exposure can’t be prevented are key to reducing risks.

Understanding the variety of concerning diseases carried by animals, both common pets and livestock as well as wildlife, can help promote better public health through informed prevention and treatment efforts.

Evolution of the Human Diet

Meat Eating and Brain Growth

Research shows that early human ancestors began eating meat around 2.6 million years ago. This shift to a more nutrient-dense diet, rich in proteins and fats, is believed to have supported the growth of our large, complex brains over the course of human evolution (1).

Meat provided a concentrated source of calories and nutrients that fueled brain development.

One study found that adding meat to the diet led to a 20-25% increase in brain size over a period of just 2 million years (2). That’s an incredibly short time span in evolutionary terms. Eating meat offered a survival advantage, as increased intelligence helped early humans adapt to changing environments.

Cooking and Digestion

The advent of cooking around 250,000 years ago unlocked even more nutrition from meat and plants. Heating food breaks down proteins and plant cell walls, making key nutrients more digestible and bioavailable for absorption (3).

This helped early humans extract more calories from the same amount of food.

Some researchers believe cooked meat and starchy plant foods fueled the dramatic rise in the number of neurons in the human brain. Cooking meat also killed off parasites and pathogens that could have infected early human groups (4).

Food Taboos

Most cultures around the world developed food taboos prohibiting the consumption of certain animal species. These food avoidances likely emerged for several health-related reasons:

  • Toxicity – Some animals contain natural toxins or bioaccumulate toxins from their ecosystem.
  • Parasites – Meat from carnivores and omnivores poses a higher risk of transmitting parasites to humans.
  • Bacterial contamination – Shellfish and pork spoil quickly without refrigeration.
  • Human resemblance – Great apes resemble humans, making their meat seem unconscionable to some communities.

Inuits living in frigid, meat-centered environments have remarkably few food taboos, while groups from tropical climates ban a wide variety of animal protein sources (5). This demonstrates how culture and geography influence food traditions.

Legal Restrictions

Endangered Species Protection

Many countries have laws protecting endangered species from being hunted or consumed. For example, sea turtles are considered a delicacy in some parts of the world, but many species are critically endangered.

As a result, international trade in sea turtle products is illegal under CITES (the Convention on International Trade in Endangered Species). This helps prevent further declines in sea turtle populations.

Food Safety Regulations

Government agencies often regulate which meats are approved for human consumption from a food safety perspective. For instance, in the United States, the FDA and USDA inspect meat processing facilities and set standards around sanitation and disease control.

Any meats that do not meet these safety standards cannot be sold to consumers. This prevents food poisoning and the spread of contaminants like E. coli or Salmonella.

Cultural Taboos

In many cultures, certain types of animals are considered taboo to eat for religious, spiritual or cultural reasons. For example, Hindus consider cows to be sacred and do not eat beef. Jewish and Islamic dietary laws prohibit pork consumption.

Some African cultures forbid the eating of certain totem animals associated with their tribes. And in parts of Asia, dogs are considered pets, not food. These cultural taboos have persisted for centuries and shape modern-day food customs.


In summary, humans have evolved to eat a narrow range of animal foods, and many species are unsafe due to toxins, pathogens, or legal protections. By understanding the health risks, evolutionary diet, and regulations around unconventional meats, we gain important insight into which animals humans cannot eat.

While our tastes may be omnivorous, prudence is required when venturing beyond domestically raised livestock and poultry. With an informed, thoughtful approach, we can make healthy, ethical choices about the meats we consume.

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