Origin Story: A Big History of Everything

by David Christian

If indeed our universe exists in a multiverse, then we can imagine a grand throwing of the dice when our universe was created, followed by an announcement: “Okay, there will be gravity in this universe, and electromagnetism as well, and electromagnetism is going to be 1036

Like human lovers, electrons are unpredictable, fickle, and always open to better offers.

How did the first eukaryotic cells evolve? The biologist Lynn Margulis showed that they evolved not through competition but rather by a sort of merging of two existing prokaryotic species. It is common for different species to collaborate through what is known as symbiosis. Today, humans have vital symbiotic relationships with wheat, rice, cattle, sheep, and many other species. But Margulis was talking about a much more radical type of symbiosis, one in which once independent bacteria, including the ancestors of modern mitochondria, ended up living inside a cell from the Archaea. Margulis called the mechanism endosymbiosis. At first, her idea seemed crazy, because it ran counter to some of the most fundamental concepts about evolution by natural selection. But most biologists now accept her arguments. The most important

Margulis’s discovery of endosymbiosis tells us something more about the history of life. Evolution is not just a matter of competition. Nor is it just a matter of constant divergence as new species appear. We also see collaboration, symbiosis, and even convergence. This means we have to reconsider the conventional metaphor of a tree of life, because even if we still think of three domains of life, it looks as if the third domain, the Eukarya, evolved not by increasing divergence but by the convergence of Archaea and Eubacteria—rather as if two branches of an ancient tree joined up again.

But eukaryotes have a different and more complex way of passing on their genes, and they pass them on only to their offspring, never to strangers.

Indeed, cells, like kamikaze pilots, often self-destruct if they are no longer working well or no longer needed, a process known to biologists as apoptosis. Today, as many as fifty billion cells in your body will commit suicide by apoptosis.

Mass-extinction events reshuffled the genetic deck of cards, created new evolutionary spaces for survivors, and set up new evolutionary experiments.

They need up to twenty times as much energy as the equivalent amount of muscle tissue. In human bodies, the brain uses 16 percent of available energy, though it accounts for just 2 percent of the body’s mass.

Collective learning, over more than one hundred thousand years, had significantly increased human control over energy and resource flows in many different parts of the world.

Foragers used and knew about hundreds of different species of plants, animals, and insects, but farmers focused on a small number of favored species, so they developed exceptionally intimate relationships with them. Intense symbiotic relationships often lead to changes in the behavior and the genetic makeup of both species.

In the year 2000, the total biomass of all wild land mammals was about one-twenty-fourth that of domesticated land mammals.1

Humans changed, too, but in different ways. Most of their adjustments were cultural rather than genetic. Humans have changed genetically as a result of farming.

For example, if you’re descended from people who once herded cattle and consumed cow’s or mare’s milk, you will probably be able to digest their milk even as an adult because you can keep producing lactase, the enzyme that digests lactose (milk sugar). Hunter-gatherers consumed only breast milk till about four years of age, and after childhood, they no longer needed to produce lactase. But where cow’s or mare’s milk became a major food source, humans began to produce lactase into adulthood—a genetic mutation had occurred.

The largest and oldest world zone was Afro-Eurasia. This is where humans had evolved, and because there was a land bridge between Africa and Eurasia, ideas, people, and goods could move in relays over vast distances. The next-oldest world zone was Australia, first settled about sixty thousand years ago. The Australasian world zone was connected to Papua New Guinea and Tasmania during the last ice age but had the most tenuous of connections to Eurasia. The third-largest world zone, in the Americas, was settled at least by fifteen thousand years ago but was largely cut off from Eurasia when the Bering Strait was flooded at the end of the last ice age. In recent millennia, a fourth zone would emerge in the Pacific. Western islands such as the Solomons may have been settled as early as forty thousand years ago, but islands farther to the east and south (including New Zealand, Hawaii, and Easter Island) were settled during a remarkable series of seaborne migrations that began just thirty-five hundred years ago.

Climates began to warm, erratically, about twenty thousand years ago, and by thirteen thousand years ago, average global temperatures were similar to today.

summary, warmer climates made village life and farming possible in a few favored regions, population pressure sometimes made it necessary, and the reserve knowledge accumulated by foragers over many millennia provided the start-up technologies for the first farmers.

Almost thirteen million books were published between 1450 and 1500, and more than three hundred million between 1700 and 1750.