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There are about 8.7 million species of animals, plants and fungi on earth,[6] compared to an estimated 1 trillion—1 million million—types of bacteria and archaea.[7] Less than 0.001 percent of all species on the planet are eukaryotes.
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Such immense periods of time are hard for the human brain to conceptualize, but if we compressed 4.6 billion years into one calendar year then bacteria evolved in early spring. Humans don’t appear until about half an hour before midnight on 31 December.[11]
They live miles below ground and miles above it, where they influence the formation of clouds and possibly even lightning.[12] They are so numerous that, despite their tiny size, the total mass of all bacteria on the planet is thirty-five times that of all the animals and 1,000 times the weight of all humans.[13]
All plants and animals produce energy through aerobic respiration, which is twenty times more efficient than anaerobic respiration—and therefore much better suited to supporting large, multicellular organisms.
In total, phytoplankton—photosynthesizing microorganisms in the sea—account for at least half of the oxygen produced
Viruses are tiny, even by the standards of microbes. They can be hundreds of times smaller than the average bacterium. Viruses are so minuscule that they haven’t left a mark on the fossil record.
They are found anywhere that life is present and far outnumber all forms of life on earth—even bacteria. A liter of seawater contains over 100 billion virus particles, and one kilogram of dried soil somewhere in the region of a trillion.[18] The total number on the planet is estimated at about 1031—that is, one followed by thirty-one zeros.[19] But only about 220 types of virus are known to be capable of infecting humans.[20]
Phages kill between 20 percent and 40 percent of all bacteria every day,
when a retrovirus infects a sperm or egg cell, something remarkable happens: viral DNA is then passed on to every cell in every subsequent generation. An astonishing 8 percent of the human genome is made up of such genes.[22]
One remarkable example is a gene inherited from a retrovirus infection about 400 million years ago that plays a
crucial role in memory formation. The gene does this by coding for tiny protein bubbles that help to move information between neurons, in a manner similar to the way that viruses spread their genetic information from one cell to another.[23] In the laboratory, mice that had this gene removed are unable to form memories.
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If one of our distant ancestors hadn’t been infected by a virus hundreds of millions of years ago, humans would reproduce by laying eggs.
Each of us hosts an estimated 40 trillion bacteria—meaning they slightly outnumber human cells.[28] Viruses? At least ten times that figure.
In total, the human microbiome—all the microbes living in our body—weighs around the same as our brain, between one and two kilos.
The evolutionary reason why bacteria produce chemicals that improve our moods may be that it makes us more likely to be gregarious and therefore provide them with opportunities to colonize other hosts.
It has raised hopes that fecal transplants from people with healthy microbiomes will one day provide a more effective treatment for depression than Prozac or therapy.
The main alternative to the Great Men theory of history is what Lucien Febvre, the French historian, referred to in the early 1930s as “histoire vue d’en bas et non d’en haut,” or “history from below and not from above.”[35] This approach focuses on the masses of ordinary men and women, often fighting against exploitation and oppression. In this view, it is the cumulative impact of all their struggles that drives progressive social, political and economic transformations.
we will explore how viruses, bacteria and other microbes impact aggregations of bodies—that is, the body politic, body economic and body social. This is history from deep below.
Ancient skeletons have started to reveal extraordinary secrets—and lots of them. This book pulls together this ground-breaking research, much of which has been published in pay-walled scientific journals and is not widely read outside of academia,
Geneticists estimate that our last common ancestor with chimpanzees dates to between 6 and 8 million years ago.
Just over 3 million years ago, protohumans were habitually walking on two legs but the size of their brains and bodies had hardly changed—as demonstrated by “Lucy,” the female skeleton discovered in Ethiopia in 1974
Homo erectus, or “upright man,” appears in the fossil record about 2 million years ago.
first known skeletal remains with the modern anatomical features typical of Homo sapiens are the fossilized bones of five people who died some 100 kilometers from Marrakesh about 315,000 years ago.
There is both archeological and genetic evidence that we coexisted in Africa with a variety of other species of humans.[4]
Homo sapiens have been around for at least 300,000 years as an anatomically distinct species, but their apparent cognitive superiority only kicked in between 40,000 and 50,000 years ago, when they surged out of Africa and vanquished all other human species.
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The adoption of basic tools like a bone club allowed our ancestors to consume more meat, which aided brain development and set in motion a process of invention and innovation that ultimately enabled humans to conquer the planet and even outer space.
The repercussions of this discovery are seismic: Homo sapiens didn’t go through a distinct cognitive revolution; rather, modern human behavior arose at the same time as anatomically modern humans.
This process has been called the “poison-antidote model” of adaptive introgression: Neanderthals gave Homo sapiens a “poison” by exposing them to a novel pathogen, but also the “antidote” in the form of introgressed gene variants that confer resistance to the pathogen.[61] As a result, many of the Neanderthal gene variants that remain in our genome relate specifically to our immune response.
her obsession. *3 To understand the potential impact of contact between Homo sapiens and Neanderthals, consider that Native Americans and Europeans had been separated for about 17,000 years before renewed contact literally decimated the indigenous population of the Americas in the sixteenth century. Modern humans and Neanderthals were separated for at least thirty times longer. Chapter 2 Neolithic Plagues Epidemiologically, this was perhaps the most lethal period in human history. —James Scott
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Jared Diamond argued that the adoption of settled agriculture was the “worst mistake in the history of the human race.”[16]
an epidemiological revolution followed hot on the heels of the Neolithic Revolution.
It turns out that all the various samples of Yersinia pestis were related to a common ancestor that was circulating about 5,700 years ago.
It is highly likely that the sharp fall in the population that occurred in Britain and the rest of western Europe about 5,000 years ago was caused by a “Neolithic Black Death.” But this devastating epidemic differed from the fourteenth-century Black Death in one crucial respect. Yersinia pestis did not evolve into a flea-borne bubonic plague until the beginning of the first millennium BCE.[70] Prior to that it would have been transmitted by sneezing and coughing and infected the lungs.
The bacteria that caused the Plague of Justinian had genetically mutated sometime between the Bronze Age and the fifth century.[56] This adaptation allowed Yersinia pestis to survive in fleas. In fact, it made the fleas feel especially hungry so they were more likely to sink their teeth—or more precisely their mouths—into someone or something.
Within ten days or so the rat populations in an area would all die from plague, and then the fleas would move on to humans.[58]
When the climate got markedly colder in the 430s, gerbils and marmots were forced to venture beyond their traditional habitat in search of food. Sooner or later they would have come into contact with black rats and infected fleas jumped from one species to the other. Once this had happened it was inevitable that Yersinia pestis would spread throughout North Africa and Western Eurasia.[60]
The Norwegian historian Ole Benedictow estimates that roughly 60 percent of the population of Europe—that is about 50 million out of 80 million people—died from the plague between 1346 and 1353.
Over time, the waiting period became standardized at forty days—the word quarantine is derived from quaranta, the Italian for forty.
This contrasts starkly with the brutally inefficient privatized system in the U.S. The United States spends more on health care than any other country—almost $11,000 per person every year, compared to $4,300 in the UK, for example.[65] And yet health coverage is patchy. Those Americans who can afford to pay benefit from the best health care anywhere in the world. Yet tens of thousands of people die prematurely every year because they are unable to access health care.[66]
The system is so inefficient that if the U.S. had a national health service like the UK’s, its health outcomes would improve and it would save almost 2.5 trillion dollars every year. Deaton and Case point out that the dysfunction in the U.S. health care system is, in monetary terms, more of a handicap than the reparations that Germany had to pay following the First World War.
Rich nations bought far more vaccines than they actually needed; one study estimates that by the end of 2021 they had stockpiled 1.2 billion doses, despite having vaccinated their populations already.[69] That is more than enough to vaccinate all adults in sub-Saharan Africa twice.
In the UK, adults in the poorest parts of the country were almost four times more likely to die from coronavirus than those in the wealthiest areas.[71] In the U.S., death rates were four and a half times higher among the poorest people than those with
At one extreme is the laissez-faire approach taken by the U.S. government. Citing concerns about the economic impact and curtailing individual freedom, President Trump let the virus rip through the country. As a result, over a million people in the U.S. died—0.31 percent of the total population.[73] In the UK, the government imposed several lockdowns with the intention of slowing rather than halting the spread of the virus. Covid-19 killed 200,000—0.27 percent of the population.
Epidemics have played a critical role in, among other things, the transformation from a planet inhabited by multiple species of human to one in which Homo sapiens reigned supreme; the replacement of nomadic foraging with sedentary agriculture; the decline of the great empires of antiquity; the rise of new world religions; the transition from feudalism to capitalism; European colonialism; and the Agricultural and Industrial Revolutions. In other words, bacteria and viruses have been instrumental in the emergence of the modern world.
But these “heroes” didn’t bend the arc of history with their genius and force of personality; rather, these qualities allowed them to take advantage of the opportunities that had been created by devastating epidemics.
The Black Death killed 60 percent of the European population, and it was the impact of this demographic crash that triggered the struggle between feudal lords and serfs in the first place. And while the Haitians were up against the French army, one of the best-trained, best-equipped forces the world had ever seen, they managed to devise a strategy that used yellow fever as a deadly weapon.
dealing with Covid-19 was disastrous in health terms. Despite the fact that the virus originated in Wuhan, the official death rate in the U.S. is more than 300 times higher than in China; in the UK it is more than 250 times higher than in China.[4] The U.S., one of the richest countries in the world, was overwhelmed with disruption, deprivation, disease and death. China—one of the poorest societies on the planet fifty years ago—airlifted medical equipment to North America to help ease the crisis. A quarter of a century ago, American scholars could claim with straight faces that liberal
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