The terrifying creatures that endlessly pursue humans in movies like Train to Busan, World War Z, and The Walking Dead are often called zombies. They are depicted as rotting corpses, driven by an insatiable hunger for human flesh. However, from a biological perspective, such creatures are completely impossible to exist in the real world.
Why Are Zombies Biologically Impossible?
A scientific analysis reveals why the zombie apocalypse, as portrayed in fiction, is biologically implausible:
Brain Function: Zombies are typically shown as being driven by basic instincts, primarily the urge to bite and consume. However, a functioning brain, even one dedicated to such primal urges, requires a constant
supply of oxygen and nutrients. A rotting corpse would not be able to sustain the metabolic activity needed for even this minimal brain function.
Muscle Degradation: Movement, especially the relentless pursuit seen in zombie narratives, depends on intact muscle tissue. In a decomposing body, muscles rapidly break down and lose their ability to contract. Over time, rigor mortis would set in, followed by complete flaccidity as tissues decay. A zombie’s sustained, strenuous activity is biologically impossible for a decaying corpse.
Circulatory System: For muscles and any remaining brain activity to function, a circulatory system is essential to transport oxygen and nutrients and remove waste. Zombies are depicted without a beating heart or functional blood vessels. Without circulation, tissue death would be immediate and widespread, preventing any coordinated movement.
Decomposition: The most significant biological barrier to zombies is decomposition. Immediately after death, the body begins to decay due to autolysis (self-digestion by enzymes) and putrefaction (bacterial action). This process leads to the breakdown of all soft tissues. A body that has been “dead” for any significant period would simply be a skeleton or a collection of putrefied matter, incapable of locomotion or aggression.
Sensory Perception: Zombies often track victims through sight, sound, or smell. However, sensory organs—eyes, ears, and nasal tissues—are among the first to decompose. A decaying body would quickly lose any ability to perceive its surroundings effectively, rendering it unable to hunt or navigate.
Energy Source: Any living (or un-dead) organism requires an energy source to fuel its activities. While zombies might consume flesh, the digestive system of a deceased, non-functional body would not be able to process or extract energy from it. There would be no metabolic pathway to convert consumed biomass into kinetic energy.
Disease Transmission: While fictional zombie viruses or pathogens are often cited as the cause, real-world pathogens either kill their hosts or require living host cells to replicate. A pathogen that could reanimate and control a deceased, decaying body while simultaneously allowing for aggressive physical action is unknown to science.
Conclusion
While the concept of zombies provides thrilling entertainment and a rich canvas for allegorical storytelling, a thorough examination from a biological standpoint reveals that such creatures could not exist in reality. The fundamental biological processes of life, death, and decomposition directly contradict the characteristics attributed to the walking dead in popular culture.
