Has Malaria Really Killed Half of Everyone Who Ever Lived?
Across Earth's history, our planet has been home to an estimated 109 billion human beings. And according to another oft-repeated factoid, half of all the people who have ever existed were killed by malaria, the worst mosquito-borne illness. Mosquitoes aren't merely annoyances, they are mass murderers.
But is this actually true?
There's little doubt that these hellacious insects are prodigious killers of humankind. The bloodsuckers spread all sorts of diseases – West Nile Virus, various kinds of Encephalitis, Dengue Fever, Yellow Fever, and Zika Virus, for example. However, the damage wrought by all of these diseases is piddling in comparison to malaria. Causing fever, tiredness, vomiting, headaches, and seizures, it struck 216 million people in 2016 alone, resulting in between 445,000 to 731,000 deaths. Believe it or not, that's an improvement over past years. In 2000, there were 262 million cases, resulting in at least 839,000 deaths.
Adding these devastating statistics together almost unequivocably places mosquitoes as the leading killer of human beings all time. But a historical death toll of roughly 54 billion - half of all humans ever? That seems a tad hard to believe, especially considering that malaria is presently responsible for perhaps 1% of all deaths worldwide each year.
BBC journalist Tim Harford was skeptical, too. For his podcast, More or Less, he interviewed Professor Brian Faragher, Emeritus Professor of Medical Statistics at Liverpool School of Tropical Medicine.
"It's difficult to find evidence to support that claim. It's a widely published claim, but it's very difficult to find the source of it," Faragher said.
Indeed, the claim is made in articles from a wide array of traditionally credible sources, most without a link to an original source. Its earliest utterance we discovered is in a 2002 Nature article, unfortunately unreferenced: "Malaria may have killed half of all the people that ever lived."
That same year, two researchers explored the "Evolutionary and Historical Aspects of the Burden of Malaria" in the journal Clinical Microbiology Reviews. They wrote:
"At some time during the 19th century, malaria reached its global limits. In absolute numbers and in the proportion of the humanity now affected, malaria was exacting its highest ever toll of sickness and death. Well over one-half of the world's population was at significant risk from malaria. Of those directly affected by malaria at least 1 in 10 could expect to die from it."
So, even if all of the world's population in 1900 contracted malaria, the death toll would have come to perhaps 100 million. That's a lot of people, but it would have taken 540 more "1900s" to get to 54 billion deaths, an almost statistically impossible prospect.
"If you extrapolate that... and try to work out the total percentage of people who would have died from malaria... it was probably somewhere between four and five percent," Faragher said.
That's an eye-opening statistic to be sure, but it is a far cry from the original and far more share-worthy factoid. On the plus side, it does have the benefit of being far closer to the actual truth.