Humans may have as many as 100,000 to 150,000 individual hairs on our scalps, growing at a rate of roughly 1 centimeter per month.

Real-time tracking of individual hair cells has revealed that hairs don't actually get pushed out from the root—instead, hair cells are tugged upward by surrounding tissues that act like tiny motors.

We're typically born with all the hair follicles we'll ever have, just as women are born with all their eggs.

40% of women will have noticeable hair loss by age 50.

Telogen effluvium is a common, temporary type of hair loss that can be triggered by severe stress, illness, or other body changes like childbirth—it pushes as much as 70% of hair into its resting phase, causing hair to fall out.

Male pattern baldness accounts for more than 95% of hair loss in men and is characterized by thinning hair, hair loss, and a receding hairline.

Hair loss after childbirth happens because pregnancy hormones paused the normal hair shedding process during pregnancy, so the hair loss is actually your hair cycle 'catching up' with its normal process several months postpartum.

Humanity's reduced body hair slows down wound healing

Cuts to human skin take twice as long to heal compared to chimps and other mammals. Scientists argue this is due to the reduced number of hair follicles on human bodies. Hair follicles contain stem cells which help repair skin cells faster, so as humanity shed its hair over time, so to speak, it also slowed its wound healing.

Male pattern baldness is not solely inherited from the maternal side; its causes are still under investigation, but scientists think the genetic component of this type of hair loss involves multiple genes.

In 1909, a top public health official in America wrote in an academic journal that baldness was caused almost exclusively by snug-fitting hats.

Rodent research suggests goose bumps may play a role in hair growth—raising questions about if this knowledge could be used to reactive sympathetic nerves in hair follicles to boost hair growth in people.

The anatomy of our hair follicles explains goose bumps

The arrector pili muscle contracts when we're cold or scared, causing hairs to stand up and the skin to form the bumps known as goose bumps. This reaction is typically involuntary.

Late-stage clinical trials indicate that a common arthritis drug may be a promising treatment for a leading cause of hair loss.

A man’s genes can predict his hairline

There’s actually some truth to the idea that you should look at your mother’s father. But genetic research tells us that the full picture is somewhat more complicated. An interesting read on how to use genetics to figure out if you'll go bald (with illustrations).

It's been about 30 years since a new hair loss drug was approved in the US, and women currently have no approved pills for hair loss.

Scalp cooling caps may help prevent hair loss during chemotherapy by temporarily reducing blood flow to the scalp, thereby reducing the amount of chemotherapy that reaches hair follicles.

Cleopatra purportedly recommended grinding up fly heads and rubbing them on areas experiencing hair loss as a treatment.

Stress contributes to gray hair because when the body experiences stress, the sympathetic nervous system releases specific hormones that influence pigment-producing cells.

Over one million people are estimated to travel to Istanbul each year for hair transplants.

Women are born with all the eggs they will ever produce in their lifetimes

Girls are born with an estimated 1 million to 2 million eggs in their bodies, but around 10,000 die monthly before girls hit puberty. Scientists have not yet figured out why there's such an excessive number of eggs prior to menstruation, but they've calculated that there are roughly 300,000 to 400,000 eggs left at puberty.

So-called 'recession blondes and brunettes' skip hair appointments to save money

One hairstyle trend is seen as a recession indicator: people letting their hair grow darker roots instead of frequently splurging on expensive blonde highlights.

Each taste bud has 10 to 50 sensory cells that form a flower-like capsule

At the top of the structure are thin filaments known as "taste hairs" that bind taste-producing substances to the surfaces of the cell, after which corresponding electrical signals are sent to the brain. Adults have 2,000 to 4,000 taste buds on their tongue.

Humans accurately detect their goose bumps only about one-third of the time.

The halting of human bone growth helps manage heat produced from metabolism

While fish, amphibians and reptiles get bigger throughout their lives until they die, their slower metabolisms allow their bodies to regulate the resulting smaller temperature increases. In humans, hormones triggered during puberty harden growth plates, ending bone lengthening.

Bone marrow generates roughly 500 billion new blood cells each day.

British beard history, 101

The beard has gone in and out of fashion for centuries in Britain. It was hated in the 18th century but became a must in the 19th. This quick list rehashes 15 fascinating tidbits about the beard, including possible useful functions for them (a beard is equivalent to an SPF 21 sunscreen) and how barbers were often also surgeons.

Humans may be able to distinguish more than one trillion scents

That's according to one estimate published in 2014. This figure far exceeds earlier estimates of a human smelling ceiling around 10,000 odors. The newer figure is derived from experiments in which volunteers agreed to sniff varying scents. Researchers mixed odor components and had volunteers sniff the brews to detect subtle scent differences. (Some users may experience a paywall.)

Your brain appears to age in five distinct stages, with the pattern of connections inside your brain shifting, on average, around ages 9, 32, 66, and 83.

The number and quality of sperm in men's semen is down, giving rise to various movements to avoid 'spermpocalypse'

A typical fertile, healthy young man produces over 100 million spermatozoa, or sperm cells, in his testicles every day. Scientists agree sperm figures are generally moving in the wrong direction, but also emphasize there's still a lot to learn about sperm.

Cells can last in the human body from days to a person's entire life

Despite claims that a person's body replaces itself every seven to 10 years, the rate at which cells die and are replaced varies by cell type. Gastrointestinal cells that line the digestive tract and stomach last only a few days, while some heart muscle cells and most neurons are around from birth until death.

Studies estimating the number of years between human generations suggest there have been approximately 10,000 to 12,000 generations of humans.

Nasal hairs, called vibrissae, help protect the body from particulate matter and other dirt

The nose structure plays a key role in filtering air before it enters our lungs and makes sure that the air temperature and humidity are also suitable for the body.

Watch DNA replicate itself before cell division

In the average adult human, between 50 billion and 70 billion cells die daily, requiring them to replicate their genetic instructions before dividing into new cells. This process relies on various proteins to unwind, read, build, and proofread new strands, with error rates of fewer than one per 1 billion nucleotides.

Most cells undergo programmed, controlled death

In the average adult human, apoptosis occurs in 50 billion to 70 billion cells daily when proteins managing a cell's life cycle send signals that the cell is damaged, causing it to break apart into smaller pieces that are consumed by white blood cells. The consumption prevents damage from spreading via cell division.

Because it loses more atmospheric gas to outer space than the cosmic dust it collects as it moves through space, the Earth loses about 50,000 metric tons of mass every year.

Cells cannot grow forever due to escalating inefficiency in transporting chemicals

As cells get larger, their volume grows much faster than the surface area through which nutrients and waste products pass, creating a bottleneck that eventually causes cells to die. This forces nearly all organisms visible to the naked eye to comprise enormous numbers of smaller cells, such as the approximately 30 trillion found in the average adult human.

Everything scientists could learn by looking at your skull

Our skulls are all unique, but they also share characteristics across groups of people. In the absence of fingerprints, forensic scientists can learn a lot about you just from your skull.

The body's master clock has 20,000 neurons

The suprachiasmatic nucleus, the master clock in mammals, has 20,000 neurons that help maintain the light-dark cycle in the body. Among its jobs: It receives light input information from the retina and then signals peripheral body clocks to act on this information, driving everything from body temperature to hunger.

Mapping how human population has grown throughout history

It took 200,000 years for our human population to reach 1 billion—and only 200 years to reach 7 billion. When will our global population peak? And how can we minimize our impact on Earth's resources, even as we approach 11 billion?

Each part of the human body experiences aging differently

With global average life expectancy cresting at 73 years, understanding how the body ages is imperative to effective medical treatment and maintaining a desired quality of life. This 13-minute video dives into how the body and its organs age "from head to toe."

Adults may lose roughly 3% of their muscle mass each decade after 30.

Tardigrades typically live between 3 and 30 months

While avoiding predators, including other tardigrades, nematodes, snails, mites and some fungi, these organisms feed on decaying plant matter and cellular fluid, which they access by puncturing cell walls with their stylets—spear-like structures within their mouths.

See what loud noises do to inner ear hair cells

This animation illustrates how louder music can affect inner ear hair cells. Damage to these cells is generally considered permanent. Hearing protection like ear plugs can reduce the level of sound entering into the ear and help protect those cells.

Long-term goose bumps are something to flag to your doctor

Although rarely a cause for concern, persistent goose bumps with no known cause could be a symptom of something to discuss with your doctor, including anxiety, a hair follicle blockage, or conditions that arise from an overreaction of the autonomic nervous system.

Women tend to tip more often than men

For instance, among people who visit hair salons or barber shops, 62% of female respondents said they always tipped. Only 45% of men said the same. This article includes more takeaways and stats about how Americans tip, and who receives them.

Goose bumps require a surprisingly complex series of steps

Watch an anatomical breakdown of how goose bumps work—featuring real skin from a human cadaver, a segmented brain, and a detailed anatomical model of the skin—to learn about all the jargon behind goose bump science. (Warning: Includes graphic footage of cadaver skin.)

The history of skull modification

The ancient Maya people sometimes modified their skulls to appear more conical. Body modification has been a human pastime for literal ages, from piercings to bindings and everything in between. Modifying one's skull shape may have been a way to symbolize status, beauty, belonging, or belief. The health impacts of such practices are still debated. This article explores the history and health impacts of skull modification, also known as artificial cranial deformation.

The evolution of the human brain

The human brain, in all its staggering complexity, is the product of millions of years of evolution. Read on to find out about brain size and intelligence, language and brain development, and more.

Chemotherapy is a cocktail of powerful drugs that slows cancer by interfering with cell division.

Why do humans have such long childhoods?

Humans have over twice as long childhoods than other animals with similar lifespans like whales and elephants. A human child can grow for nearly 20 years before they become a reproducing adult. Researchers believe there's a connection between long childhoods and human's unusually large brain size, though the science is not totally clear. Dive into what scientists know here.

The human brain only uses 5% more energy during active tasks versus resting

Despite only being 2% of the weight of a human body, the average adult brain consumes 20% of its energy, with the majority of it spent on maintaining homeostasis—the stable equilibrium conditions of temperature, acidity, blood sugar, and other properties in the body. For infants, the consumption is closer to 50%.