The Body Summary

Your body is the most extraordinary thing you’ll ever own. It’s worth understanding just how incredible it truly is.

1. Building a Human is Far More Complex Than It Seems

Although you might assume that assembling a human is just about gathering the right ingredients, creating life is an unfathomable marvel. A human body consists of 59 different elements, with carbon, oxygen, hydrogen, nitrogen, calcium, and phosphorus making up the bulk of it. However, even with all these elements, the process of animating them into life is beyond human capability.

At its core, life starts with a cell, the smallest living unit. Yet scientists are still uncertain about how cells come together to form a fully functional human. This question remains one of the greatest mysteries in biology. Each cell contains a meter of DNA, which acts as the instruction manual for everything that makes up a person, from eye color to susceptibility to certain diseases. The life encoded in DNA has been passed along from ancestors who lived billions of years ago, showing the interconnectedness of human evolution.

Interestingly, if we tried to “create” a human today, estimations on the material cost vary wildly—from £96,546.79 to just $168 depending on the study. However, producing sentience and consciousness isn’t something that money or materials can replicate. This highlights the miraculous complexity of our existence.

Examples

• A 2013 calculation estimated the total cost of building Benedict Cumberbatch from scratch at nearly £100,000.
• The Nova science program argued the cost could be as low as $168, showing how estimates vary.
• DNA’s continuous replication and transmission links us to ancestors from three billion years ago.

2. Microbes: Your Tiny, Vital Companions

Your body isn’t just yours—it's home to trillions of microbes that play essential roles in keeping you alive. They aid digestion, bolster immunity, and regulate many bodily functions. Without them, human life wouldn’t exist.

Gut bacteria are among the most crucial microbes, helping break down food and extract nutrients. In fact, they produce thousands of digestive enzymes compared to the mere 20 enzymes humans produce naturally. Microbiota, the collective term for these tiny organisms, are sometimes considered an additional organ because of the wide array of benefits they provide.

Despite their importance, human interaction with microbes has a dangerous side. Overuse of antibiotics kills beneficial bacteria alongside harmful ones and leads to increased antibiotic resistance. This ongoing challenge underscores the delicate balance between harnessing microbes for our benefit and avoiding long-term harm.

Examples

• The average person has around 40,000 microbial species living inside and outside their body.
• Gut microbes provide up to 10% of the calories we consume.
• Penicillin, derived from mold on cantaloupe, revolutionized microbial medicine but also creates antibiotic resistance.

3. The Brain: Your Body’s Command Center

The brain is one of the most incredible structures ever discovered. Although it looks like a soft, tofu-like blob and constitutes only 2% of your body weight, it controls everything you do, think, feel, and perceive.

The brain operates at peak efficiency, only needing around the energy of a blueberry muffin per day. It contains approximately 86 billion neurons that form trillions of connections, creating a network more complex than a supercomputer. These connections allow psychological processes, emotions, sensory experiences, and movement.

The brain consists of three main sections: the cerebrum, cerebellum, and brainstem, each responsible for specific functions like thought, balance, and vital processes. Smaller components, like the hypothalamus, control hunger, aging, and even sexual function, showcasing its far-reaching influence.

Examples

• The brain uses about 20% of your body’s daily energy.
• Human brains are similar in relative size to mice brains but vastly more complex due to the trillions of neural connections.
• The hypothalamus, a peanut-sized structure, regulates thirst, hunger, and even aging.

4. Blood: The Lifeline of the Body

Circulating through your entire body, blood is vital for carrying oxygen, fighting infections, and maintaining health. On average, your heart pumps about 260 liters of blood every hour, ensuring nutrient delivery and waste removal across your 37 trillion cells.

Blood consists of plasma, red and white blood cells, and platelets. Plasma, mostly water, acts as the fluid medium. Red cells carry oxygen, white cells combat infections, and platelets help with clotting and tissue repair. Historically misunderstood, blood is now at the forefront of medical diagnostics.

Despite advancements, reproducing artificial blood has proven difficult. Transfusions remain the most reliable way to treat blood-related conditions, though storing blood presents challenges.

Examples

• A healthy heart beats roughly 3.5 billion times over a lifetime.
• Platelets were once a mystery but are now known to regenerate tissue in addition to clotting blood.
• Antibiotics help cure blood-borne infections but also reduce healthy bacteria.

5. Hormones Make It All Happen

Hormones are the messengers that carry chemical instructions across your body. They are involved in virtually everything, from controlling blood sugar to influencing emotional connections.

For example, diabetes is caused by insufficient production of insulin, a hormone that regulates blood sugar. Before the discovery of synthetic insulin, diabetes was often fatal. Hormones like oxytocin, known as the hug hormone, not only create bonds between people but also assist during childbirth and in practical tasks such as facial recognition.

Scientists today know of at least 80 hormones, and they are still discovering new ones. Hormones are the invisible driving forces behind countless human functions and behaviors, though much about them remains unknown.

Examples

• The invention of injectable insulin in the 1920s saved countless lives.
• Oxytocin helps women during labor while also fostering emotional warmth between couples.
• The pituitary gland, just the size of a baked bean, influences height and growth.

6. Humans: Engineered for Movement

The human body has evolved in remarkable ways to make bipedalism—walking on two legs—possible. This unique trait has shaped our anatomy and even contributed to painful processes like childbirth.

Bones, muscles, and tendons work in harmony to support movement. Humans have evolved longer necks, flexible spines, and specialized thumb muscles for tool use. Back pain is a common downside of our upright posture, as our spines remain a structural adaptation in progress.

Childbirth, too, has been impacted by bipedalism. Narrower female pelvises accommodated walking upright but made labor far more challenging and painful. This process showcases evolutionary compromises.

Examples

• Humans have 206 bones, but some, like sesamoid bones, vary individually.
• The opposable thumb is enhanced by unique human muscles, such as the flexor pollicis longus.
• Walking upright causes many chronic back problems due to anatomical strain.

7. You Truly Are What You Eat

The foods we consume shape our bodies in profound ways. Cooking, for instance, allowed humans to extract more nutrients from food, cutting down chewing time and helping us develop smaller teeth and weaker jaws. However, modern diets, particularly excess sugar intake, often harm more than help.

Sugar consumption is a particular problem. The average American consumes 22 teaspoons of added sugar daily—over four times the amount recommended by health organizations. Even natural products like fruit have been bred to have higher sugar content.

Our digestive system is adept at breaking down all sorts of foods, absorbing nutrients in the intestines and expelling waste. Still, we often overload it with more sugar and fat than it was designed for.

Examples

• Cooking food kills toxins and improves digestibility.
• Fruits today contain far more sugar than their natural ancestors.
• The intestines are responsible for absorbing nutrients and eliminating 14,000 pounds of waste per lifetime.

8. Sleep: The Great Reset

Despite being one of our most necessary activities, sleep remains poorly understood. It’s a time when our bodies rest, memories consolidate, hormones reset, and immune systems recharge. But why consciousness needs to pause remains a mystery.

Circadian rhythms guide our sleep habits, as do newly discovered cells in the eyes that detect light and regulate the body’s natural clock. Individuals’ needs vary, with babies requiring significantly more sleep compared to adults.

Seasonal changes also affect the body’s internal clocks. From hair growth rates to mood shifts, humans respond to nature even if we’ve largely forgotten to pay attention.

Examples

• Newborns sleep up to 19 hours per day as their bodies develop.
• Special cells in the eyes detect brightness irrespective of vision.
• Studies show that hair growth speeds up during summer months.

9. Life and Death: The Ultimate Journey

Life expectancy has soared over the past century. Improved medicine, better sanitation, and healthier diets have all contributed. However, death remains inevitable, with chronic diseases like cancer and heart conditions becoming the leading causes as communicable diseases decline.

Healthcare has addressed countless diseases, but one remains eradicated: smallpox. Meanwhile, genetic and lifestyle diseases pose new challenges. Aging, too, is an unsolved biological process—no one escapes its effects.

Though death’s physical manifestation is visible, parts of the body and many microbes remain “alive” after a person dies. This stark reality reminds us of the fragility and awe-inspiring complexity of living.

Examples

• Smallpox, once deadly, became the only disease humans have eradicated.
• Fewer than 1 in 10,000 people live to age 100.
• Chronic pain, like cancer itself, stems from biological faults rather than evolutionary function.

Takeaways

1. Appreciate your body by maintaining a healthy diet, exercising regularly, and getting enough sleep—it’s designed to thrive with movement and care.
2. Limit your sugar intake and avoid unnecessary antibiotics to support both your gut microbes and overall health.
3. Be proactive about medical research for the diseases most affecting your lifestyle or loved ones, as prevention and understanding are continuously evolving.