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How many people have lived on planet Earth?
Researchers estimate how many humans have ever lived.
It's easy to think that our lifetime and the world around us is unique and definitive. But thinking about how many people have ever lived on this planet can add some perspective to our instinctive self-centeredness. And it's not only a matter of how many people lived before we appeared, but how many have died.
So what's the answer? According to estimates by demographic researchers at the Population Reference Bureau (PRB), as of 2015, there have been 108.2 billion who have ever been born. Taking away the roughly 7.4 billion who are alive today, we get 100.8 billion who have died before us.
There are almost 14x more people dead than alive! That would make for one massive army of zombies, ghosts and White Walkers. Or, if you prefer to be more optimistic, you can think that the living are about 6.8% percent of everyone who'd ever lived. For the sake of simplicity (and to take into account the people born in the past year), lets round up the percentage to 7. We are the 7%. Let's make the most of it!
How do the researchers come up with these estimates? The starting point that the Population Reference Bureau takes for the beginning of what it considers human history is 50,000 BC, when the modern Homo Sapiens appeared. This date in itself is debatable as early hominids walked the earth millions of years ago. The date of 50,000 BC is taken from the United Nations Determinants and Consequences of Population Trends.
Coming up with how many people were born after that is certainly based on informed speculation. Plagued by low life expectancy (up to 10 years during the Iron Age) thanks to lack of medicine, food supply issues, climate changes, killing each other and other problems, human population grew at a slow rate. Early infant mortality was as high as 500 infant deaths per 1,000 births or higher.
Here's a chart from PBR estimating how population expanded (at least until 2011).
Interestingly, you can see how the rate of growth was lower from 1AD until 1650 AD, mainly due to such events as the outbreak of the plague, known as Black Death. You can also see the great population expansion from about the time of the Industrial Revolution to our current day. From 1850 till now, the planet's living population increased by about 6 times!
Certainly, some of these numbers are to be argued. The researchers made guesstimates on the birth rates and set a constant rate of population growth, which surely fluctuated. Still, this estimate gives us a useful perspective on our place in the life of our planet.
Here's Carl Haub from PRB talking about his methodology:
The team caught a glimpse of a process that takes 18,000,000,000,000,000,000,000 years.
- In Italy, a team of scientists is using a highly sophisticated detector to hunt for dark matter.
- The team observed an ultra-rare particle interaction that reveals the half-life of a xenon-124 atom to be 18 sextillion years.
- The half-life of a process is how long it takes for half of the radioactive nuclei present in a sample to decay.
A study looks at the ingredients of a good scare.
Catching fear in a bottle<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDYyNzg1Ny9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyOTQwMTcyMn0.WtpJ1E_dhK2o09fBpKARynj4_p5NXeklgsXsbd7xr9w/img.jpg?width=980" id="8ff51" class="rm-shortcode" data-rm-shortcode-id="f10dd9188b173f4a36e85e9325507c6b" data-rm-shortcode-name="rebelmouse-image" />
Credit: Photo Boards/Unsplash<p>Previous studies have tracked physiological signs of fear arousal, but none have established a one-to-one correlation between that arousal and specific, actual fear events.</p><p>Andersen says that much of the research has been conducted in lab settings with weak fear stimuli, observing subjects as they experience things like scary videos. Scares in these situations tend to be weak and difficult to measure. Even harder to track in these situations is the link between enjoyment and fear. </p>
Eyes everywhere<iframe src="https://player.vimeo.com/video/109695164" width="100%" height="480" frameborder="0" scrolling="no" class="rm-shortcode" data-rm-shortcode-id="267ba87cfb8591ed5830499574d2272a"></iframe><p>Andersen and his colleagues conducted their experiments at <a href="https://dystopia.dk" target="_blank" rel="noopener noreferrer">Dystopia</a> Haunted House, a commercial attraction in Vejle, Denmark constructed in an old, run-down factory. The Recreational Fear Lab has a long-standing partnership with the spook shack.</p><p>They outfitted 100 volunteers with heart monitors and sent them on their terrifying way through the 50-room horror mansion. The facility incorporates a number of fright mechanisms including frequent jump scares in which a sudden threat takes a visitor by surprise.</p><p>Researchers surreptitiously observed their participants on closed-circuit video as they made their way through the attraction. They tracked each individual's scares, scoring them for intensity according to their visible reactions. After exiting the attraction, individuals self-reported their experiences in the haunted house.</p><p>Combining these self-reports with observer notes and each participant's heart-rate data gave the researchers subjective, behavioral, and physiological insights into the ways in which fear is experienced, and when it's a good thing or not.</p>
A pair of inverted U-shapes<p>In analyzing their data, the researchers saw two separate inverted u-shape curves. One depicted participants' enjoyment based on their self-reports and observed behavior. A similar u-curve was detected in their heart rates showing that just the right amount of heartbeat acceleration is associated with fun, but too much is too much. It's the terror Goldilocks zone.</p><p>Says Andersen, "If people are not very scared, they do not enjoy the attraction as much, and the same happens if they are too scared. Instead, it seems to be the case that a 'just-right' amount of fear is central for maximizing enjoyment."</p><p>The research suggests that being scared is enjoyable when it represents just a quick minor physiological deviation from one's normal state. When it goes on too long, however, or triggers too severe a physiological change, it becomes disturbing. Game over.</p><p>Andersen notes that this is not dissimilar to the factors known to make interpersonal play enjoyable: just the right amount of uncertainty and surprise. These are, maybe not coincidentally, also the ingredients of a successful joke.</p>
A meteorite that smashed into a frozen lake in Michigan may explain the origins of life on Earth, finds study.
- A new paper reveals a meteorite that crashed in Michigan in 2018 contained organic matter.
- The findings support the panspermia theory and could explain the origins of life on Earth.
- The organic compounds on the meteorite were well-preserved.
Meteor streaks through Michigan sky<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="80b7f30820153b35fc515592d7475f53"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/EPu2qnqMYBo?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
The meteorite that smashed into Strawberry Lake carried pristine extraterrestrial organic compounds.
Credit: Field Museum