When you stop to think about it, humans are pretty amazing animals. Not only have we managed to stick around in various forms for millions of years, but we've also grown into a population of more than 7 billion, scattered virtually all over the planet. And we've done it despite being fairly fragile creatures. We're not particularly strong; we lack a tough hide or fur to protect us from the elements; we don't do very well without a regular supply of food and water; and we're vulnerable to a lot of infectious diseases.
So what has enabled us to thrive to the point where, for the most part, we don't spend every waking moment worrying about whether we'll live to see another day? Our saving grace, perhaps, is our highly developed brain and its ability to experiment with, dream up and collaborate on ingenious solutions to life-threatening challenges. There are a multitude of inventions that modern humans depend on to sustain their existence, but here are a few we would find it extremely difficult to live without.
We've all heard the expression "no need to reinvent the wheel," meaning that a solution already exists for the problem at hand. This saying has added significance when you consider the many ways in which the wheel improved human life, and how long mankind lived without it.
Archaeologists debate when the wheel was first invented. The earliest evidence of a wheel in human history occurs at about 3500 B.C.E. in Mesopotamia, but this evidence is associated with the wheel's use in pottery-making, not as a tool for transportation. It took another 300 years or so for the people of Mesopotamia to realize that the wheel could also help them to move things from place to place [source: Gambino].
Wheels evolved in a few stages, beginning with the use of logs as rollers to facilitate transportation and continuing on through the replacement of rollers with wheels that rotate on an axle [source: ThinkQuest]. By 2000 B.C.E., wheeled chariots appear in the archaeological record throughout ancient Egypt. Only by then the wheels had spokes, making them considerably stronger and lighter.
The wheel was probably the most important mechanical invention of all time. Just about all modern mechanical devices use the wheel in some way – cars, buses, bicycles, factory machines, toys, wristwatches, movie reels and more. Not to mention the wheel's continued use for pottery-making and transporting goods by cart -- both of which ancient peoples must have appreciated.
Sure, the wheel was probably a literal lifesaver for ancient humans, but you can't hunt a boar by sticking a wheel in its side, and you'll have a hard time skinning a pelt from a bear by running a wheel over it. As Crocodile Dundee would say, "That's not a knife."
That's why we come to the blade -- and its iterations as an axe, a knife and so on -- as a breakthrough that literally saves the lives of humans. In fact, new research has shown that stone tools like a blade didn't just allow humans to eat better, wear better protective clothing and make for a good fight scene in "West Side Story." It appears that 1.7 million years ago when tools began to be formed by human ancestors, they actually contributed to the evolution of how our hands work [source: Reardon].
Even before that, early humans were using sharp stone flakes and hand axes to hack at meat. An excavation in the Afar region of Ethiopia led anthropologists to declare in 2012 that human ancestors were using butchering tools nearly 3.4 million years ago [source: Viegas].
Let's start with the first breakthrough when it came to human fashion: We lost our fur. Sure, bare skin is all the rage these days, but it wasn't always the style. Researchers now suggest that humans might have developed a less Robin Williams-type look around a million years ago. They propose that early humans were at risk of overheating their brain if they couldn't cool their skin by sweating, a trick that's a lot easier when you're not dealing with tangled, dense fur [source: Connor].
Once we lost our body sweaters, however, we faced a greater risk of exposure to the elements, so we had to put on some clothes. It's hard to determine exactly when humans started wearing coverings; animal pelts don't make good artifacts because they decompose [source: Upton]. (Not to mention that hides were used for shelter and other uses besides clothing.)
So researchers at the University of Florida did something pretty cool. They decided to see when clothing lice split genetically from head lice [source: Toups et al.]. (Did you even know the two were different?) Turns out that 83,000 to 170,000 years ago -- just around an ice age -- clothing lice came into existence, as did, researchers assume, clothes. So for hundreds of thousands of years, we did have a ball running around naked. But clothes, whether pelt or pashmina, have literally saved our lives innumerable times since then [source: Viegas].
Now that we have wheels, blades and clothes, what were early humans to do with all our cool stuff? Just carry it around all day? No. We needed one more breakthrough to make life a little easier, if not actually save human existence. (Also, disclosure: None of those discoveries happened in that order.)
That brings us to shelter. Now, let's not pretend that shelter is a unique breakthrough that only humans discovered. We definitely started off like most animals -- just finding a good place to hide. For our early ancestors, that probably even meant living in nests in trees. Of course, caves and rock outcrops were probably popular choices, too.
As long as 2.6 million years ago, there were signs that early human groups began collecting food and tools to bring them back to certain favorite watering holes or sleeping spots [source: Smithsonian]. About 800,000 years ago, we start seeing fire and hearths added to the mix. But our earliest evidence of a man-made shelter comes from 400,000 year-old postholes and other archaeological evidence in Terra Amata, France [source: Smithsonian]. By building shelters, humans were not as vulnerable to their environment and could survive harsher conditions.
Let's fast-forward to more modern times for our next lifesaving breakthrough. When the British Medical Journal asked a group of experts and readers what the greatest scientific advancement in the last 150 years was, the answer wasn't open-heart surgery or the find-my-phone app on smartphones. Beating out antibiotics and anesthesia, the majority chose advancements in sanitation [source: Katz].
The discovery that proper disposal of urine and feces could save lives wasn't so long ago. It was in Victorian England, where the Thames was glutted with waste and sewage overflowed in the streets, that former journalist and lawyer Edwin Chadwick decided that an ounce of sanitary prevention was certainly worth the cure of typhus, cholera, influenza and many other nasty germs that came with exposure to sewage.
Chadwick drafted plans for hydraulic sewage systems and drainage pumps to remove waste (one of those pathways led directly to the Thames). Of course, proper sewage disposal is still not present globally, and with great consequences: One billion people – 15 percent of the world's population -- still practice open defecation, and 2.4 billion will use unimproved sanitation facilities by the year 2015 [source: WHO/UNICEF].
Speaking of contaminated water, drinking the stuff can lead to a miserable bout of stomach pain and loose bowels, as many of us who've traveled in the developing world can attest. But water-related illnesses do more than just ruin trips. As the World Health Organization reported in 2005, such diseases are the world's leading cause of death, claiming 3.4 million lives annually -- more than war, terrorism and weapons of mass destruction combined. Children in impoverished countries, whose immune systems already are weakened by malnutrition and other stresses, are particularly at risk [source: VOA].
It used to be even worse. For centuries, even in developed countries, mysterious, periodic outbreaks of water-borne cholera regularly killed many thousands of people [source: Encyclopaedia Britannica]. During a cholera outbreak in 1854, British scientist John Snow determined that the disease was caused by microorganisms in sewage that contaminated the water supply. Among other pioneering public health ideas, he came up with the suggestion to apply chlorine to the water to kill the microorganisms, and the illness rate plummeted. Since then, additional chemical and filtration technologies have been developed to make our drinking water much safer [source: Lenntech].
We don't know the identity of the experimenter or experimenters in the Acheulian culture in Africa who discovered how to start, control and use fire about 790,000 years ago. But their mastery of rapid oxidation was one of the most important developments that sustained the survival and spread of humanity, according to Nira Alperson-Afil, a member of an Israeli archaeological team that found the earliest evidence of human ability to make and control fire at will [source: Hebrew University of Jerusalem].
The invention equipped early humans with a scary deterrent -- flaming torches -- to protect them and their vulnerable young from predators. It also provided a source of warmth that helped them to survive temperature downturns. In addition, the ability to cook animal flesh and vegetation increased food choices for humans and helped them to avoid malnutrition. Perhaps more than any other invention, fire was the breakthrough that enabled humans to multiply and spread across the planet's surface.
Today, we've progressed beyond gathering around the campfire and gnawing hunks of charred mammoth haunches, but the ability to burn fuel remains a crucial part of our continued existence.
If we didn't have farms to produce food for us, we'd all have to spend much of our time gathering wild plants and stalking animals to survive, the way primitive hunter-gatherers did thousands of years ago. Hunting and gathering isn't necessarily a bad way to go. For example, its inherent flexibility enables humans to use the available resources in a range of habitats efficiently, and it doesn't deplete the ecosystem the way modern civilization does [source: Washington State University]. But it would require us to continually be on the move and limit ourselves to relatively small groups. Contemporary civilization -- from standing militaries to factories to shopping malls -- would be impractical. That's why the development of agriculture is so important to our survival.
Agriculture really is not one, but a series, of scientific and technical breakthroughs -- such as the development of irrigation technologies, and the invention of crop rotation and fertilizers -- that occurred over thousands of years. But it all started when humans figured out how to gather seeds from wild plants, plant and tend them, and harvest them. According to DNA analysis of modern foodstuffs, development of the "founder crops" -- wheat, barley, chickpeas, lentils, flax and others -- dates back about 9,000 to 10,000 years in southwest Asia [source: Harris].
For most of human history, virtually everyone on the planet faced the risk of dying in epidemics of bacterial diseases that sometimes ravaged multiple continents. One such disease, bubonic plague -- the "Black Death" -- killed an estimated 200 million people in the 14th century alone [source: BBC].
Then, in the late 1920s, a London physician named Dr. Alexander Fleming, who was trying to develop an antibacterial agent, noticed mold that had contaminated a petri dish inhibited the growth of a pathogen he was studying. Fleming published a scientific article on his discovery in 1929, and one of his students, Dr. Cecil Paine, eventually became the first clinician to demonstrate the effectiveness of penicillin, a drug derived from the mold, against bacterial disease in human patients [source: Wong]. Since then, the use of penicillin and other antibiotics has led to reductions in the mortality rate from certain infections like syphilis, septicemia and, of course, bubonic plague [source: Hemminki and Paakkulainen]. Interestingly though, antibiotics can't claim all the credit when it comes to decreased mortality rates in common bacterial diseases. Other breakthroughs on our list, like clean water, have a big role to play, too [source: Hemminki and Paakkulainen].
The cans of refried beans in your pantry might seem like a humble advance in civilization, but there's a reason civil defense officials advise everyone to keep a supply. The ability to preserve foodstuffs for long periods without refrigeration enables people to survive natural and man-made disasters that disrupt our electrical supply and make it difficult to obtain supplies of fresh food.
Canning was invented in the late 18th century out of military necessity. Napoleon's troops were suffering more casualties from hunger and scurvy, a nutritional deficiency, than they were from combat with the enemy, and the French government offered a prize of 12,000 francs to anyone who could develop a method of preserving soldiers' provisions in the field [source: Can Manufacturers Institute]. A Parisian named Nicholas Appert, who had worked variously as a candy maker, chef and beer brewer, came up with the idea of partially cooking food, sealing it in bottles with cork stoppers and then immersing the bottles in boiling water to expel the air inside. He believed the air caused it to spoil. (It would be another half century before Louis Pasteur would discover that heat actually killed the microorganisms that spoiled food and caused illness.)
French soldiers took Appert's samples of poultry, vegetables, gravy and other items along with them when they were sent on an overseas voyage, and they reported that after four months, it remained edible. In 1810, English inventor Peter Durand received a patent for an improved food container, which had a soldered lid instead of a cork. Two years later, two of Durand's countrymen, Bryan Donkin and John Hall, opened a factory that put food into metal cans instead of bottles [source: Can Manufacturers Institute].
Animal testing has a long, gruesome history, but it's also saved countless human lives. Learn more about animal testing at HowStuffWorks.
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