How Much Caffeine Is In A Cup Of Tea?

When most people think about measuring caffeine, they regularly use coffee (yuck, can't stand the stuff) as the universal measuring stick. Me, I'm a solid tea drinker. Breakfast, lunch, dinner... any time of the day is tea time for me. And yet, I never feel like I'm tweaking out or having a caffeine rush when I ingest tea. I've long known how much caffeine is in a cup of tea, but for the betterment of mankind...

...and to spread a little bit of 'Oh wow, cool' knowledge...

How much caffeine is in a cup of tea?

Well, the answer is surprising, but it'll all make sense by the time I finish explaining it.

When measured in their dry form, tea leaves actually contain more caffeine per gram than coffee grounds. And yet, it takes many less leaves to produce a single cup of tea. If you were to make an 8 ounce cup of tea, you would use approximately 2 grams of tea leaves to steep in the water. For the same size cup of coffee, you would need 10 grams of coffee grounds. As such, the increased supply of coffee grounds means more caffeine is brewed into the beverage. The final tally? That 8 ounce cup of tea has approximately 40 milligrams of caffeine. The 8 ounce cup of coffee has roughly 105 milligrams of caffeine. That's nearly three times as much! Coffee wins the caffeine race by a landslide.

Now, let's take this one step farther. The amount of caffeine in a cup of tea is also influenced by a few different factors. The location of the leaves on a tea plant helps to determine their caffeine content; younger leaves near the top have more. Also, steeping a tea bag longer in a cup of hot water also releases more caffeine. Generally, you should steep a tea bag for at least four to five minutes for optimum flavor. Finally, the type of tea you use also dictates how much caffeine you take in. White and green teas have less caffeine. Oolong tea has a moderate amount. Black tea has the most.

The chemical structure of Caffeine.

Also take note -- the antioxidants in tea slow down the caffeine absorption process in your body. As such, the caffeine is used at a much more gradual rate, meaning you don't experience an energy crash at the end. The caffeine will stay with you longer and have a more prolonged, less severe effect.

And there you have it! All you would ever want to know about caffeine in relation to tea. Doesn't this make you want to have a cup? I know I do!

The Hardest Part Of The Human Body.

When one thinks of the hardest, most durable parts of the human body, there are some obvious guesses that could be made. The skull? Maybe the hip? Perhaps your femur?

No, no and no.

Believe it or not, the hardest part of the human body is in your mouth. Tooth enamel, the outermost layer of your teeth, is the most adamantine structure you possess. Enamel is largely composed of hydroxyapatite, which is a crystalline calcium phosphate. As such, it is stronger than any bone you have.

And yet, even tooth enamel has its weaknesses. What you eat determines the longevity of your enamel and overall dental health. Sugar is extremely destructive to enamel. Why? Because sugar acts as a food source for oral bacteria. As sugar comes to rest on your teeth, bacteria feed on it. This produces lactic acid. Accordingly, the lactic acid lowers the pH in the mouth. With a lower pH, the mineral structure of the hydroxyapatite in your enamel begins to erode, allowing bacteria to further invade the interior of a tooth. It's a endless cycle, ultimately leading to a tooth rotting out if not treated. Also harmful to tooth enamel are various acids, like that found in your gastrointestinal system or from soda pop. Of note, a hard-bristle toothbrush can also wear away the enamel over a long period of use. Soft-bristle toothbrushes are the way to go!

This is what sugar does to your mouth. It leads to enamel loss, allowing bacteria to invade and destroy your teeth.

Your tooth enamel will serve you a lifetime if you take care of it. Brush twice a day and limit your sugar intake as much as possible. Do that and the hardest substance in your body stay that way.

How Does An Atomic Clock Work?

We all know the importance of clocks. They keep us running on time. Without them, we'd miss soccer practice and school, dentist appointments and weddings. The clock is a highly important tool, perhaps in the upper echelon of humanity's greatest inventions. But what about atomic clocks?

Just to alleviate your fears... no, atomic clocks don't run on nuclear power.

The base function of time-keeping with an atomic clock is grounded in atomic physics (not nuclear physics as many may believe). Using the electromagnetic transition frequency found within atoms, an atomic clock bases its mechanism of measurement against this standard. More often than not, atomic clocks rely upon the microwave signals that electrons emit in an atom when they change energy levels.

So how do atomic clocks work? With lasers. Coooooool!

Pew. Pew. Lasers are so rad.

Using captured atoms in a microwave-filled atomic fountain (a cloud of atoms tossed upwards by lasers in the Earth's gravitational field), atomic clocks employ said lasers to slow atoms down dramatically. In fact, the atoms are slowed to nearly absolute zero. That's frigid! Once the atoms are slowed to almost a standstill, the are probed to measure the time difference between the electrons changing their energy level.

At this point, you may be asking "Jared, what atoms are used to measure time in an atomic clock?" Good question! Atomic clocks rely upon a standard measurement found within caesium-133. As the only stable isotope of Caesium, the International System of Units (SI) defines the second as the duration of 9,192, 631, 770 cycles of radiation relating to the transition between two energy levels of the caesium-133 atom.

Click to enlarge

That's a lot of technical jargon, but essentially, the most accurate time measurement known to man is all thanks to the element caesium.

Because atomic clocks measure the second on the atomic level, they are the most accurate time measurement tools on the planet. The National Institute of Standards and Technology (NIST) is the chief time keeper for the United States, through which much of the world also relies upon. Their current premier clock, the NIST-F2, has been online since 2014. Current evaluations of NIST-F2 place its accuracy at an amazing 300 Million years before it will lose a second. If you've ever synced your computer's clock to internet time, then you may have noticed the time.nist.gov weblink. This is the NIST's website, which helps keep all of our computers, mobile devices and GPS units running accurately. Thanks NIST!

The NIST-F2 Atomic Clock

And there you have it. Atomic clocks keep our technological world running accurately and efficiently. When you look at your smart phone for the time, or map your coordinates on a GPS device, you're employing lasers and atomic physics. Doesn't that feel awesome?!

Gasoline Has A Short Lifespan.

A short note on gasoline this evening, thanks to an uncooperative lawn mower...

A can of gasoline blended with ethanol will not last as long as you might think.

The average shelf life of E10 gasoline is approximately three months or less. With the adaption of blended fuels in the modern automotive era, the life span of gasoline has grown much shorter. This is chiefly due to moisture absorption. Ethanol-blended fuel absorbs water at a much faster rate. If E10 gas is left in a can with any manner of leaks, or in an area prone to temperature fluctuations, it will absorb the ambient moisture in the air and become unsuitable for use in an engine.

Remember folks -- keep your gasoline stored in a secure, airtight manner. Do not let water mix with the gas. Keeping the cap on is important!

How Do The Transformers Rubsign Stickers Work?

Every child of the 1980's remembers the original Transformers toys. They featured these really cool, heat activated stickers that you could touch. Moving your finger back and forth across these rubsigns, as they're known, revealed the allegiance of the robot. Were they an Autobot or a Decepticon? All you had to do was check the rubsign!

Shockwave's rubsign was on the left side while in blaster mode. I'd bet $20 he's a Decepticon. When's the last time you saw a purple Autobot?

Implementing the rubsign was a novel idea by Hasbro, the creator and manufacturer of the Transformers. While the sticker served as a bit of a gimmick for the toys, it also acted as a mark of authenticity. Beginning in 1985, many toy competitors started to flood the market with cheap knock-off Transformers. The legally patented rubsign was in place to prove that a Transformer was authentic.

At its core, the rubsign sticker is like a flat mood ring. Inside the sticker are thermochromic liquid crystals. These crystals change shape as the heat they're exposed to increases. As such, this molecular change reflects at different wavelengths of light. The more a rubsign sticker is heated up by touching it, the brighter it gets. Over time, as the rubsign cools down, the liquid crystals return to their original structure and lose their color.

This is an original commercial from 1985 proclaiming the importance of the rubsign to indicate a genuine Transformers toy.

Who knew that the Transformers were using cutting edge science in their implementation of the rubsign and fending off crooks at the same time? That's radical!

Ant-Man's Stomach Could Solve World Hunger.

I recently watched the Marvel film Ant-Man. I enjoyed the movie as it was -- a simple, straightforward redemption / heist movie that didn't take itself too seriously. The plot was fairly thin, but oh well. What more could you expect? It's about a guy that can shrink.

The movie got me to thinking, though. Ant-Man could solve all of the problems of the world, if he were real at least. As a fictional character, his abilities create a massive plot-hole in the Marvel Universe.

While we all know that Ant-Man can become incredibly tiny, but what most casual film-goers and comic readers don't realize is that he can also grow upwards in size. Ant-Man is also known as Giant-Man! His growth powers work in both directions, both smaller and larger.

WARNING - SCIENCE AHEAD!

The Pym Particles that give the Ant-Man suit its powers cause the wearer inside to grow or shrink in proportion. His or her body maintains its structural form, but the ratio at which it changes stays as-is. Hence, the wearer looks and changes a great deal, but the alteration to size is totally relative.

Now, consider the contents of the Ant-Man's body when it changes size. What about the food and water in his stomach, which also grows or shrinks directly proportional to the Ant-Man? If he ate a corndog and drunk an eight ounce glass of water before growing into the Giant-Man, the items in his stomach would also become larger. There'd be a chewed, partially digested corndog in his stomach. That eight ounces of water would compound, becoming hundreds (perhaps thousands) of gallons of water.

The power of the Ant-Man suit could solve world hunger in a flash. It could also solve the rapidly worsening drinking water crisis. Those Pym Particles could eliminate hunger and starvation, thereby ending the chaos and violence associated with it. Imagine that... a world with a food and water surplus. Want to create the world's biggest bread loaf? Have Ant-Man swallow a capsule with a tiny piece of bread, then let him grow into Giant-Man. After twelve hours and a moment on a humongous toilet, you'd have a titanic piece of bread.

It's like Jesus feeding the multitudes with two fish and fives loaves of bread, only far more plausible!

Yet, such a notion would never be applied to the fictional Marvel Universe. If Earth were suddenly free of the genuine problems facing humanity, there'd be very little reason to fight and destroy super-villains. Many of the evil forces that heroes like Ant-Man / Giant-Man face would simply disappear. Humanity would enter into a golden age of peace and prosperity.

All because Ant-Man could grow stuff in his stomach.

Racial History Months Are Divisive And Racist.

I find the concept of month-long celebrations centered around a certain race to be prejudiced and highly divisive.

Now, before you pull the race card and call me a bigot, let me explain.

Humanity, as a whole, is 99.9% alike. Take two random people from opposite sides of the world and compare their DNA. What you'll find is that they're almost identical. If you were to study these two samples anonymously without knowledge of who donated which DNA, you'd probably have a difficult time discerning which sample belonged to which person. The only differences, that 0.01%, are merely variables that affect how and why we may develop certain diseases or peculiar health conditions.

All humans are related and extremely similar. Hence, a person's ethnic heritage (race) is completely inconsequential.

Local student Walter Gadsden is attacked by police dogs during the Birmingham civil rights protest on May 3, 1963. Did the dogs attack Gadsden because they knew he was 'black', or because they were trained to do so by the police?

Photo by Bill Hudson.

Race, by and large, is a social construct that mankind has generated to divide people. We label groups of humans by certain names based upon purely superficial features. This person has slanted eyes. This person has dark skin. This person has curly hair. None of these surface features reflect any sort of genuine biological division between people -- they're merely reflections of various genes (found within a very tiny portion of our entire genome) being turned on or off.

In essence, race does not exist. Alternatively, you can state that there is only one race -- the human race.

How does this relate to a month celebrating one particular race of people? I'll explain.

February is Black History Month. Irish-American History Month is in March. Hispanic Heritage Month is from September 15 to October 15. I could go on and on with more examples, but you get the idea. Each of these months serve as a period to single out and celebrate one particular 'race' of people over another.

This is akin to celebrating Red LEGO Brick Heritage Month or Green Skittles Awareness Month -- it just doesn't make any sense.

If all of humanity is equal and related (which it biologically is), then what purpose is there to sequester and elevate a particular group of people that generally match the preconceived societal notions attached to a specific race label?

Much less, how can you define the boundaries of a race? Are there certain qualifiers to being a member of a race? Do you have to look a certain way? Must your facial features be of a certain size? Does your skin have to be a certain color tone? Who is to say what one race is and is not? Would the judgment of one person on the definition of a race not be completely and wholly subjective in nature? Take my own genome for example, which has genetics tracing to Africa, Asia, Europe and North America. Which 'race' am I?

Which of these men are 'black'?

Trying to define a race is as arbitrary as defining the borders between states or countries. It's all just a bunch of imaginary lines saying one side is mine and one side is yours. These lines don't actually exist. There is no separation between black or asian, white or hispanic.

There are only human beings. No imaginary lines. No invented labels.

When we celebrate race-based history months, we're perpetuating three negative and dishonest concepts:

• That human beings are divide by stereotypical, superficial features.
• That the history of all people should not be uniformly celebrated in equal measure.
• That a particular group of people aren't as important the other eleven months out of the year.

To put it bluntly, raced-based history months are, for lack of a better word, racist.

It's not that I don't want only one particular race to have a month-long celebration. I don't want any month-long celebrations for anyone based upon the color of their skin. Your (yes, you the reader) ancestral history is unique and diverse, full of struggle, hardship and joy. Your forefathers and foremothers fought against hatred and bigotry, famine and disease, war and death. They crossed great oceans overflowing with peril and mountain ranges full of danger. They loved and cared for each other in times of great happiness and disastrous loss. They traveled from all corners of the globe, representing the migration of one enormous human family. Your ancestors were light skinned and dark skinned, tall and short, curly haired and even freckled. They had round eyes and almond-shaped eyes. Your family tree has branches tracing back to all sorts of people, from all walks of life.

You are the living, breathing embodiment of diversity, no matter what you look like on the outside. You are not just a divisive label. You're so much more than that... and your history deserves to be revered throughout the entire year.

Forever.

"I look to a day when people will not be judged by the color of their skin, but by the content of their character."

-- Martin Luther King, Jr.

Using The 'Flash To Bang Method' To Measure Storm Distance.

Let's say you're out camping in the wilderness. As you're roasting your fifth hot dog on the campfire, you suddenly hear the low rumble of thunder off in the distance. Before long, you're zipped tight in your tent and trying to avoid becoming a roasted weenie yourself! Lightning bolts are crackling all around you. The wind is howling. Rain is slamming against your tent, daring you to stay.

You've just been caught unprepared in a thunderstorm. OH NO!

Thankfully, there's a little trick which you can use to determine the distance of a thunderstorm. It requires no advanced mathematical ability, nor pen or paper. All you need is to know how to count.

The next time you want to determine how far away a storm is, employ the flash to bang method. It's simple, folks.

• Watch for a lightning flash.
• Start counting.
• Stop counting when you hear the bang of thunder.
• Divide the number of seconds you counted by five.
• Your result is how far away in miles the storm is.

Here's an example.

10 Seconds (from flash to bang) ÷ 5 = 2 Miles

It's really that easy. This is a very old trick that's been put to good use for ages. Now you can be just a little bit safer in your outdoor adventures! Instead of guessing how far away a thunderstorm is, you can know ahead of time before it arrives. Perform the flash to bang method in regular intervals to determine if a storm is moving closer to or away from you. For a more detailed scope of potential danger, check for lightning strikes from multiple angles to triangulate the storm's direction.

Now get back to roasting that weenie!

Do Crocodiles Really Cry?

We've all heard the old saying "crying crocodile tears". It's often said to imply that a person's appearance of remorse isn't genuine. I've often wondered, though... do crocodiles really cry?

Turns out, a crocodile is a blubbering, teary-eyed mess almost all the time.

When a crocodile cries, it's obviously not for sentimental reasons. They don't have any sense of guilt when eating a meal. Do you cry when you eat a hamburger because you feel sorry for the cow? I sure as hell don't. In actuality, the act of crying is related to a few much more simple reasons that are based totally on biological necessity.

Crocodiles have evolved to possess three eyelid membranes. This is due to their aquatic nature. Each layer allows for them to see under water, as well as protect their eye from damage while swimming or eating. When crocodiles emerge to the surface or come on shore, they must maintain a necessary level of lubrication to keep those eyelid membranes in proper working order. Therefor, they "cry" to lubricate their eyes.

Another simple explanation comes from how crocodiles make noise. They snarl, huff and grunt regularly as a form of communication. These intense sounds send reverberations throughout their skull and into their sinuses. As air is pushed through the sinus cavities near their eyes, it cause the tear glands to naturally push fluid out.

So yes, crocodiles do actually cry. It seems the old concept of "crying crocodile tears" actually does make sense after all!

What Happens To The Human Body After We Die?

We've all seen crime scene investigators on television describing the human body in various states of decay. They'll toss out a plethora of terms and phrases to describe what is happening... but how do we know what they're saying is correct? This got me to thinking. What exactly happens to the human body after we die? Of course, I mean this in a very literal sense (discussions on the afterlife are a whole different article entirely). I present to you... the stages of death in the human body!

Within the first hour after death, the human body relaxes. All of the muscles become flaccid and loosen up. This period is called primary flaccidity. Your skin also becomes saggy and droops. All of the blood in your circulatory system drains from the smallest vessels and begins to pool inside the body. As such, the skin loses its warm glow and becomes remarkable pale. This step is known as pallor mortis. With the blood not moving anymore, the human body's temperature begins to drop and match that of its environment, known as algor mortis. This drop in temperature is fairly linear. Forgoing any extreme levels of heat, cold or humidity, an investigator or mortician can roughly determine how long a person has been deceased based upon how cold they are. Two degrees Celsius (3.6 degrees Fahrenheit) are lost in the first hour, with one degree Celsius (1.8 degrees Fahrenheit) lost for every hour after that until the room temperature is met.

By hour two, the body has started to look fairly strange. All of the blood that has begun to pool in the body has gravitated to the lowest resting point, a step labeled as livor mortis. For example, a person whom died on their back will naturally pool all of the blood supply towards their backside. The massive amounts of blood will turn the skin in the area red and purple. This coloration is called the postmortem stain.

Roughly three hours past death, the human body begins to stiffen, commonly known as rigor mortis. The first areas to stiffen are along the neck and jaw, as well as the eyes. Over the course of three more hours, the stiffening spreads from the face to the abdomen, then to the arms and legs. The final areas of the human body to experience rigor mortis are the fingers and toes. The level of rigidness the body experiences will continue to build for approximately twelve hours after death. Obviously, various factors like heat and position can affect this process slightly, whether faster or slower. By the end of rigor mortis, the body is very difficult to move. Arms and legs will be all but impossible to flex. Hands and fingers make take on a gnarled appearance.

After reaching a peak level of inflexibleness, the muscles within the human body then begin to decay. Beyond twelve hours post death, the joints and limbs slowly begin to loosen up again, called secondary flaccidity. Between one and three days later, rigor mortis disappears in reverse order. If a body is left in a cold environment, this process will take longer than normal. If left in a warm area, the process will be expedited. When it's all said and done, the body will once again be flexible and relaxed.

Now, if you ever come across a dead body, you'll roughly be able to tell how long it has ceased to function!

The Invisible Man And The Future Of Cloaking Technology.

In terms of the Universal Monsters, the Invisible Man is probably my most favorite. Released in 1933, The Invisible Man was a revolutionary film with dazzling special effects for the era. Many of the effects were completed through a particularly difficult process for the time. Claude Rains, the actor whom portrayed the Invisible Man, wore a black velvet suit and was filmed against a black velvet backdrop. Complete scenes were then matted over this footage to simulate his invisibility. While that may seem like a simple task today, it was nearly impossible to construct in 1933. The Invisible Man was universally praised for this accomplishment in film making. For its importance to the history of cinema, the movie was added to the United States National Film Registry in 2008 for preservation by the Library of Congress.

Needless to say, The Invisible Man is one hell of a good film.

Astonishingly, implementing actual invisibility is something that's closer to reality than you may think.

The cloaking technology implemented by the Predator is eerily similar to what current scientific efforts are hoping to achieve.

Many research teams and engineers across the globe are actively researching invisibility technology. Most applications of this research involve varying degrees of cloaking technology and the use of metamaterials (materials engineered to have properties not yet found in nature). Such technology bends or refracts the light that strikes a cloaked object, thereby rendering it invisible. Other cloaking techniques simply allow light photons to pass through them, as if nothing was there. A research team at the University of California, Berkeley successfully demonstrated this to be possible on the nanoscale level with the use of metamaterials. Other research teams have seen promising results through the use of nanobots, which can singularly bend light around an object as it actively moves through an environment.

While current research indicates that the method of invisibility seen in The Invisible Man is probably not achievable, we will be able to cloak objects and people through more rudimentary means in the near future. Considering many objects can already be rendered invisible to radar and atmospheric surveillance, I suspect we'll achieve invisibility within my lifetime. How cool is that?!

Newly Discovered Raptor Zhenyuanlong suni Had Wings.

Say hello to the Velociraptor's nasty, feather-covered cousin.

This is the newly discovered dinosaur Zhenyuanlong suni. It was alive roughly 125 million years ago during the Cretaceous Period. Paleontologists recently found a near-complete skeleton of it in the western province of Liaoning, China. It was perfectly preserved in rock. The magnificent wings which it bore were clearly visible surrounding the fossil. This marks the largest feather-covered dinosaur ever found.

As with other members of its family, Zhenyuanlong suni was a land-bound predator. It didn't use its wings for flight. Instead, the feathers were merely used for display -- either to scare off other predators, attract a potential mate or establish superiority in a community.

It's now commonly believed that many more dinosaurs bore feathers than previously thought. One of the chief concerns with the ever-popular Velociraptor is that it most certainly had feathers or wings as well. I recently covered this discrepancy in my review of Jurassic World. While we can't wholly fault a fantasy film for incorrectly depicting dinosaurs, I do hope the day will come where dinosaurs are more accurately envisioned when brought to the big screen.

The discovery was made by scientists from the University of Edinburgh and the Chinese Academy of Geological Sciences

Humanity Is Crippled By Fear.

I sit alone in my home this evening. There's no one but my dogs to keep me company. My thoughts this evening turn to notions of mankind. What drives us? What makes us tick? Where are we going? How are we to ever survive the future? Most importantly, how are we to ever survive each other? It seems fear drives a great deal of what we do. We're afraid that foreigners will terrorize our cities. We're afraid of losing our homes, our loved ones. We fear being unloved. At the heart of it all, I believe we're most afraid of our own self.

Fear is a powerful tool; it's one that's been employed by tyrants and barbarians for countless thousands of years. Fear makes a man do something he wouldn't normally do, even when there's little at stake. We stop at red lights out of fear of being struck by another vehicle. The consequence of being burned by fire is another tangent of fear. In many cases, fear can be a positive thing. It keeps us from making repeated mistakes. Fear also makes us abuse our children. It can turn a loving husband into a jealous control freak. Fear can make us stick our head in the sand. It's funny how fear possesses multiple faces, much like a harlequin with a new mask for every performance.

I'm intrigued with the human condition, in so much as how it works with exploration. Mankind used to be very eager to break the bonds of this planet. We put men on the moon. We sent probes beyond our own solar system. Our desire to explore the outermost reaches of our own universe were once a driving force in technological development. Yet, here we are in 2015. The most highly anticipated piece of technology is the Apple Watch -- something none of us need. I'm deeply saddened at how mankind has taken two steps back from the future. What are we doing? Shouldn't we be thinking about expanding mankind's grasp of our universe? I realize Earth is our home, but just as birds, we can not stay in the nest forever. At some point, we must stretch our virgin wings and fly from the nest, seeking a new life. There's only a limited bank of resources at our disposal on this planet before we run out of options. I don't want to wait until the last possible moment to develop a strategy for future survival. The time to explore is now. Let us leave no star unseen, no distant planet untouched. Earth isn't just our home -- the entire universe is our home.

The only thing prohibiting mankind from sailing the vastness of our universe is fear. We're afraid to evolve our mindset, our field of scope, our willingness to think outside the box. Why couldn't we construct a terradome on the moon and establish a space colony? We have the materials at hand to withstand the diminished atmosphere of the moon. Supplies could be transported there, though admittedly the journey would be arduous. Yet, what ever came from not accepting a challenge? Are we not human beings? Are we not capable of overcoming adversity? Where is our sense of bravery?

Fear. I say to you again. Fear.

Fear chains mankind to the past. Courage is the key that unlocks our future.

Fear is the lengthened shadow of ignorance.

- Arnold H. Glasow (1905 - 1998)

How Women Came Before Men... and Nipples Too!

After seeing some rather disturbing misinformation earlier in the day, I thought I'd quickly cover some scientific data in a very simplified manner. Specifically, I want to explain how women existed before men.

A classic television couple -- Ralph and Alice Kramden of 'The Honeymooners'.

To my friends, both scientific and brainy; I realize this explanation will be very basic. I don't want to delve too deep into the specifics of gender determination because it would go over most folks' heads. I'm 'dumbing it down' on purpose for the benefit of the layman. Bear with me.

When a fetus begins to develop in the womb, it starts out as a simple mass of cells. Over a number of weeks, these cells slowly start to form the basis of the human body. At some point around weeks six through eight, the sexual chromosomes of the fetus determine which sex it will become. Women, in terms of a chromosome pair, are identified by XX. Men are identified as XY. To be specific, the Y chromosome is the determining factor in the sex of the fetus. The presence of the Y chromosome is what makes a fetus grow into a male. The X chromosome has no power over this choice; only the Y chromosome will produce a male child. By default, all fetuses would become female if not for the presence of the Y chromosome. Both the X and the Y chromosome are allelic mutations from ancient autosomes in mammals. What's an autosome, you ask?

A diagram of all twenty-three human chromosome pairs.

An autosome is a chromosome pair that does not determine the sex of a creature. As humans, we have a total of twenty-three pairs of chromosomes. Twenty-two of those pairs are autosomes -- meaning they do not have any influence on the gender we develop into as a fetus. The final twenty-third chromosome pair that we possess DOES control our sexual development (it's known as an allosome).

After the fetus detects the presence of the Y chromosome , it grows into a male. It couldn't be any simpler. One reflection of this shared origin between males and females are our nipples. How many times have you heard someone ask in jest "Who do guys have nipples?"

The reason behind it is simple. Men and women both have nipples because all mammals develop this feature at an early stage as a fetus. All fetuses, whether eventually determined to be male or female, develop identically before the sex is selected. The presence of nipples is one of those non-sex based factors that develop. Due to how evolution has worked in mammals, the presence of nipples (or the lack thereof) has not been a trait which was turned "on or off" by natural selection (it simply wasn't "important" enough). By default (yet again), we all get nipples. 

So there you have it my friends. I can't make this explanation any simpler. When you first started to develop as a fetus (essentially a proto-female), you were by default going to be a girl. You grew nipples (at least I hope you did). Are you a man by chance? Then your allosome had a Y chromosome in it. Congratulations!

Any questions?