The curve of binding energy

9.86 – 9.33 billion years ago

More on stardust and us.

Looking at the abundance of different elements in the universe, we get the following:

Note that the vertical scale is exponential. Each tick marks a hundred-fold increase in abundance over the tick below, so there is vastly more hydrogen and helium in the universe than any other element. As noted in the last post, all the elements except hydrogen and helium were formed after the Big Bang, spewed out by supernovas and the collisions of neutron stars. In general, heavy elements are less abundant because it takes more steps to produce heavy elements than light ones. But the curve is not smooth. The lightest elements after hydrogen and helium (lithium, beryllium, boron) are relatively rare, because they get used up in the nucleosynthesis of heavier elements. And there is a saw tooth pattern in the chart, because nucleosynthesis favors atoms with even numbers of protons. So we get lots of oxygen, magnesium, silicon, and iron, the main constituents of our planet. Lots of carbon too. Finally, iron (Fe) is more than 1000 times more abundant than might be expected based on a smooth curve. Iron nuclei are especially stable because binding energy, the energy that would be required to take the nucleus apart into its constituent protons and neutrons, reaches a maximum with iron. Here’s the famous curve of curve of binding energy (nucleons are protons and neutrons):

An implication of this curve is that if you can split a really heavy nucleus, of Uranium-235 say, into smaller nuclei (but still heavier than iron), you will release energy equal to the vertical difference between U-235 and its lighter fission products (not shown) on the vertical scale. This is lots of energy, way more than you get from breaking or forming molecular bonds in ordinary chemical reactions. And if you can fuse two light nuclei, of hydrogen say, into a larger nucleus, you can get even more energy. When we split uranium, we are recovering some of the energy that colliding neutron stars put into synthesizing the heaviest elements. When we fuse hydrogen, we are extracting energy left over from the Big Bang that no star got around to releasing. (This doesn’t violate the Law of Conservation of Energy, because the negative gravitational potential energy of the universe cancels the positive energy represented by the matter. So the total energy of the universe is zero.)

Starting to figure this all out was part of a scientific revolution that made physics in 1950 look very different from physics in 1900. The new physics resolved a paradox in the study of prehistory. Geologists were pretty confident, based on rates of sedimentation, that the Earth had supported complex life for hundreds of millions of years. But physicists couldn’t see how the sun could have kept shining for so long. The geologists were right about deep time; it took new physics to understand that the sun got its energy from fusing hydrogen to helium (via some intermediate steps).

As the scientific revolution in atomic physics was picking up steam, it was natural to assume that it would be followed by a revolution in technology. After all, earlier scientific revolutions in the understanding of masses and gases, atoms and molecules, and electrons and electromagnetism, had been followed by momentous innovations in technology: the steam engine, artificial fertilizers, electrification, radio, to name just a few. But in some ways, the Atomic Age hasn’t lived up to early expectations. The atom bomb brought an earlier end to the Second World War, but didn’t change winners and losers. The bomb was never used again in war, and it’s a matter for debate how much the atom bomb and the hydrogen bomb changed the course of the Cold War. Nuclear energy now generates a modest 11% of the world’s electricity (although this number had better go way up in the future if we’re serious about curbing carbon dioxide emissions). And a lot of ambitious early proposals for harnessing the atom never got anywhere. Project Plowshare envisioned using nuclear explosions for enormous civil engineering projects, digging new caves, canals, and harbors. Even more audacious was Project Orion, which developed plans for a rocket propelled by nuclear explosions. Some versions of Orion could have carried scores of people and enormous payloads throughout the solar system. Freeman Dyson, a physicist who worked on the project, said “Our motto was ‘Mars by 1965, Saturn by 1970.’”

On the purely technical side these plans were feasible. There were concerns about fallout, but the problems were not insurmountable. Nevertheless both Plowshare and Orion were cancelled. Regarding Orion, Dyson said “… this is the first time in modern history that a major expansion of human technology has been suppressed for political reasons.” The history of the Atomic Age  and its missed opportunities is one more refutation of pure technological determinism. How or even whether a new technology is exploited depends on social institutions, politics, and cultural values.

Speaking of which, Where Is My Flying Car?

Green revolution

November 1970 – August 1974

The battle to feed all of humanity is over. In the 1970s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. At this late date nothing can prevent a substantial increase in the world death rate.

Paul Ehrlich. The Population Bomb. 1968

Ironically, it was just around the time that Ehrlich wrote this that production of rice and wheat in India, the Philippines, and other countries was booming thanks to the Green Revolution – more productive plant varieties that could take advantage of fertilizer and pesticide inputs. It’s true, as Malthus pointed out long ago, that exponential population growth can eat up any conceivable increase in agricultural output. But the Green Revolution bought the world some breathing space until birth rates began to come down. It probably also eased some of the paranoia about food supply that played a part in two world wars, and the rural discontent that fueled earlier peasant revolutions.

Norman Borlaug, Green Revolution pioneer, awarded Nobel Peace Prize, 1970

Whoever makes two ears of corn, or two blades of grass to grow where only one grew before, deserves better of mankind … than the whole race of politicians put together.

Jonathan Swift

Steam engine time

The steam engine was a child of seventeenth century science; the Scientific Revolution gave birth to the Industrial Revolution. That’s not at all the conventional story, but David Wootton’s recent book The Invention of Science: A New History of the Scientific Revolution makes the case.

According to the conventional story, the steam engine resulted from the work of generations of inspired tinkerers, ingenious craftsmen with no particular scientific training and no great scientific knowledge. Indeed, according to one historian, “Science owes more to the stream engines than the steam engine owes to science.” (After all, the steam engine did inspire Carnot’s thermodynamic theory.)

But Wooton traces a path from scientific theory to practical application, beginning with the seventeenth century science of vacuum, air and steam pressure. The pioneering scientists here were not just theorists. They built (or at least designed) a number of devices for making use of differences in gas pressures, including an air gun (Boyle), a steam pressure pump (della Porta), and a vacuum-powered piston (von Guericke). Huygens took up the last idea, using an explosion to empty air from a cylinder, through a valve, and then using the partial vacuum to move a piston. This in turn was taken up by Denis Papin, a French Protestant medical doctor and mathematician, who worked as an assistant to Huygens, and then to Boyle. Papin combined scientific knowledge and engineering experience to design several steam engines. None of these was very practical – sadly Papin ended his life in failure and poverty. But the first of them was very similar to the first commercially viable steam engine, produced by Newcomen in 1712 – so similar that many historians have been convinced that Newcomen must have been familiar with Papin’s design.

Up to recently there’s been no convincing account of how Newcomen could have learned of Papin. But now Wooton has discovered the likeliest link, a book by Papin with the unpromising title A Continuation of the New Digester of Bones. The book has been neglected by historians, not surprisingly, but sold well in its own day. It gives plans for a pressure cooker (hence the title). But it also contains detailed descriptions both of vacuum powered piston, and of the use of steam condensation to produce a vacuum: just what Newcomen needed to put together to build his first engine. Wooton writes:

Newcomen’s steam engine is a bit like a locked-room plot in a detective story. Here is a dead body in a locked room: How did the murderer get in and out, and what did he use as a weapon? … We cannot exclude the possibility that Newcomen went to London and met Papin in 1687 … But we do not need to imagine such a meeting. With a copy of the Continuation in his hands, Newcomen would have known almost everything that Papin knew about how to harness atmospheric pressure to build an engine. … From this unintended encounter, I believe, the steam engine was born.

He concludes:

Historians have long debated the extent to which science contributed to the Industrial Revolution. The answer is: far more than they have been prepared to acknowledge. Papin had worked with two of the greatest scientists of the day, Huygens and Boyle. He was a Fellow of the Royal Society and a professor of mathematics. … Newcomen picked up … where Papin began. In doing so he inherited some of the most advanced theories and some of the most sophisticated technology produced in the seventeenth century. … First came the science, then came the technology.

A cycle of Cathay

1108 – 1158 CE

The innovations which make their appearance in East Asia round about the year 1000 … form such a coherent and extensive whole that we have to yield to the evidence: at this period, the Chinese world experienced a real transformation. … The analogies [with the European Renaissance] are numerous – the return to the classical tradition, the diffusion of knowledge, the upsurge of science and technology (printing, explosives, advance in seafaring techniques, the clock with escapement …), a new philosophy, and a new view of the world. … There is not a single sector of political, social or economic life in the eleventh to thirteenth centuries which does not show evidence of radical changes in comparison with earlier ages. It is not simply a matter of a change of scale (increase in population, general expansion of production, development of internal and external trade) but of a change of character. Political habits, society, the relations between town and country, and economic patterns are quite different from what they had been. … A new world had been born.

Jacques Gernet. A History of Chinese Civilization, pp. 298-300

Scholars contemplating the sweeping economic, social, and political transformation of China under the Song dynasty (960-1279) seem compelled to draw analogies with later dramatic occurrences in Europe – with the Renaissance (as in the quote above) or with the Economic Revolution in England on the eve of the Industrial Revolution.

The changes are dramatic. Population roughly doubles, from about 50 million to about 100 million. Cities grow. Both internal and external trade boom. The division of labor advances, with different households and different parts of the country specializing in “goods such as rice, wheat, lighting oil, candles, dyes, oranges, litchi nuts, vegetables, sugar and sugarcane, lumber, cattle, fish, sheep, paper, lacquer, textiles and iron.” In a number of fields of technology – iron production, shipbuilding – China reaches heights which the West will not attain for many centuries.

With changes in the economy come changes in the relation between society and state. Taxes come to be mostly collected in cash rather than kind. Eventually revenues from taxes on commerce, including excise taxes and state monopolies, will greatly exceed those from land tax. A Council of State will put constitutional checks on the power of the emperor.

Yet Imperial China will ultimately follow a different, less dramatic developmental pathway than Europe. Some reasons why:

Missing Greek science and math. The Greeks figured out the shape of the Earth (it’s a sphere) by the fourth century BCE, and Eratosthenes produced a fairly good estimate of its circumference in the third century BCE. The news spread: educated Muslims and Christians in the Middle Ages knew the earth was round. Remarkably, however, China didn’t get the message, or didn’t pay it much attention. The standard cosmological model in China was a round heavens above a flat, square Earth, until Jesuits in the seventeenth century convinced the literati otherwise. And, while China had a sophisticated mathematical tradition (including an ingenious method of solving systems of linear equations with rods on a counting board, equivalent to Gaussian elimination), the massive mathematical legacy of the Greeks didn’t get that far. In his recent history of Greek mathematics, Reviel Netz argues that this alone is enough to explain the “Needham question” of why China did not produce a scientific revolution.

Church, state, and kin. Europe and China arrived at very different bargains between an imported ascetic otherworldly religious tradition, an imperial state, and patrilineal kin groups.

“Without the towering synthesis of the Principia there would have been no Newtonianism to define the eighteenth and nineteenth centuries, arguably no Enlightenment, and a very different trajectory to modern history. But, working backward, without Galileo and Kepler, there would have been no Principia, and … both Kepler and Galileo would have been strictly impossible without conic sections. … Kepler and Galileo, and their entire generation turned to conic sections because they had Archimedes. … Conic sections … emerged exactly once in history – as the parting shot of the generation of Archytas and as the central theme of the generation of Archimedes. Take away these two generations and you take away the tools with which to make a Newton. … Europe, rather than China or India, produced the scientific revolution because, unlike the other major civilizations, Europe had the resources of Greek mathematics”

A New History of Greek Mathematics pp. 497 et. seq.

The nomad brake. By 1000, Western Europe has largely tamed its barbarians, folding them into a settled, stratified, Christian society. But the civilized folk bordering the Eurasian steppe, in Eastern Europe and continental Asia, are in for a rougher ride. During the whole Song period, China faces a threat from nomads to the north. In the Northern Song period (960-1126), the Khitan empire, founded by steppe nomads, occupies Mongolia, Manchuria, and part of northern China. In the Southern Song period (1127-1279), the Song lose all of northern China to a new barbarian dynasty, the Jin. Finally, the Song dynasty ends when all of China is conquered by the Mongols under Genghis Khan and his heirs, with the loss of about a third of the population. For all the wealth and sophistication of the Song, the succeeding native Chinese dynasty, the Ming, does not regard them as a model to be emulated.

Rice economics. Rice is the main food crop in southern China, the most populous and developed part of the country. Here’s a basic fact about rice versus wheat production (hat-tip pseudoerasmus): diminishing marginal returns to labor are less pronounced with rice than wheat. In other words, with rice, you can produce a lot more if you’re willing to put in a lot more work. With wheat, you more quickly reach a point where additional labor yields little additional production. This simple fact has far-reaching implications. Imagine an economy with two sectors, agriculture and manufacturing. And imagine that population expands up to a Malthusian limit. Under these assumptions, and given standard economic reasoning, it makes a big difference whether the principal crop is rice or wheat. With rice (diminishing marginal returns less pronounced), equilibrium population density is greater, output per capita is less, and more of the labor force is in agriculture, less in manufacturing.

So an economic model incorporating information about labor productivity of rice and wheat seems to account for some basic differences between China and the West. But rice cultivation may have more subtle implications.

Rice psychology. An older generation of humanist scholars was willing to generalize about Chinese thinking.

It is quite clear to all those who have been in contact with this world that it is quite different from the one in which we ourselves have been moulded. … China does not know the transcendent truths, the idea of good in itself, the notion of property in the strict sense of the term. She does not like the exclusion of opposition, the idea of the absolute, the positive distinction of mind and matter; she prefers the notions of complementarity, or circulation, influx, action at a distance, of a model, and the idea of order as an organic totality. … Chinese thought does not proceed from an analysis of language. It is based on the handling of signs with opposing and complementary values.

Gernet p. 29

Within the social sciences, sweeping pronouncements like this are suspect. To hard-headed materialists and quants they look hopelessly impressionistic and unscientific. To post-colonialist critical theorists, they reek of old-fashioned, condescending Orientalism. But there is now a substantial body of research demonstrating real differences in cognitive style across cultures, and between the West and China (and other East Asian societies), in line with the quotation above.

Of note here: there is also regional variation within China. Rice paddy farming requires high levels of cooperation, including joint work keeping up irrigation systems, and reciprocal labor exchanges. And research shows that there are differences in psychology as well between wheat and rice growing regions in China. Chinese from rice growing regions are more inclined to holistic, context dependent thinking. Chinese from wheat growing regions have a more independent, individualizing cognitive style. In other words, the expansion of rice cultivation in China may have reinforced some of its characteristic cognitive inclinations.

In conclusion: the history of the Song period poses in particularly clear form the “Needham puzzle” of why the Industrial Revolution did not originate in China. The answer, it seems, is complicated, combining (at least) political and social responses to external threat, the nature of agricultural economies, and more intangible (but still measurable) differences in intellectual traditions and cognitive style.

Weaving history

829 – 673 BCE

The association of particular plaid patterns (tartans) with particular Scottish highland clans is a phenomenon of the last several centuries. But the Celt-plaid connection goes back a lot farther than that.

This picture shows a scrap of fabric associated with the Iron Age Hallstatt culture of central Europe. The culture lasted from 800-500 BCE, and is ancestral to later historic Celtic cultures. In fact, traditions of plaid weaving seem to go back a lot further. We find similar plaids being woven at roughly the same time, but thousands of miles away, in what is now Xinjiang province in western China. Linguistic evidence (from later writing) and genetic evidence (from mummies) suggest that some of the inhabitants of Xinjiang at this point were speakers of Tocharian languages, a branch of Indo-European, deriving from the western steppes. (Both Tocharian and Celtic probably branched off the Indo-European tree long before Indo-European-speaking chariot riders rode south to Iran and India.) We know that Proto-Indo-European had words for weaving. The Celtic and Tocharian plaids are similar enough (according to those who know such things) that it seems likely that IE speakers were also weaving plaids from early on.

The Mediterranean developed its own culture of weaving. In Mycenaean Greece, slave women worked under factory-like conditions to produce cloth for ordinary wear, some of it exported. Aristocratic women too were weavers. They might work with spindles of bronze, silver, or gold, weaving story cloths – tapestries that illustrated family histories. The shroud that Penelope wove by day and unwove by night was presumably one such.

Mycenaeans used writing for bureaucratic record keeping, not story-telling. Remembering the past was the business of female weavers and male bards. When literacy disappeared during the Greek Dark Age, historic memory, such as it was, was kept going by weavers, and by bards – often called weavers of words.

Build like an Egyptian

2560 BCE

You might think that with the Egyptian pyramids being famous for thousands of years (they’re the only one of the Seven Wonders of the Ancient World still standing) there wouldn’t be much new to say about them. But you’d be wrong. The Egyptians wrote down virtually nothing about their architectural methods; they may have worked with some kind of 3-D models – the Bronze Age version of Computer-Aided Design – rather than anything like blueprints. So we haven’t really known much about how the pyramids were built. In particular, it’s been a real puzzle how they moved building blocks to near the top of the pyramid in the later stages of construction. If blocks were moved along a straight ramp up the side of the pyramid, the ramp in the last stages would have had to be a mile long, and contained as much material as the pyramid itself. It also wouldn’t have fit on the Giza plateau. Recently, Jean-Pierre Houdin, a French architect, may have figured out how the problem was solved in the case of the largest pyramid, the Great Pyramid built for King Khufu (Cheops). According to Houdin, the builders used an external ramp for the early stages of construction. But they also built a vaulted internal ramp, spiraling around insidethe pyramid, and moved blocks up it for the later stages. (And the builders economized by dismantling the external ramp and using it for construction material.) Houdin revealed his theory in 2005. Both before and since then he has put a huge amount of work into understanding how the Great Pyramid was built. For example, he may also have come up with an explanation for the 150 foot-long, narrow, slanting Grand Gallery in the pyramid: it looks like it was used to run counterweights on a trolley that helped to bring up some of the heaviest stones, the granite blocks used to reinforce the King’s Chamber.

Memory palaces

A big driver of progressive evolution, both biological and cultural , is improvements in the fidelity of inheritance. This was true back in the Proterozoic with the evolution of the eukaryote chromosome. And it’s true in human history with the invention of writing, and later with the printing press.

Writing greatly facilitates the storage and transmission of information. But even before writing was invented, people had figured out several techniques for storing large volumes of information in memory.

Poetry was one such technique. Imposing explicit, regular phonological and metric patterns on words arranged in lines, on top of the normal rules of phonology and syntax that operate in prose, can greatly facilitate memorization. The illiterate speakers of Proto-Indo-European had a considerable poetic tradition, although they probably were not doing word-for-word memorization. The Indian Brahmin heirs of this tradition, however,  were memorizing enormous bodies of text, in some cases memorizing multiple Bibles worth of literature forwards and backwards, syllable by syllable, just to make sure nothing was lost. As a result, our knowledge of ancient spoken Sanskrit has been compared to having tape recordings of the language.

Another powerful technique for memorization exploits human spatial cognition. The “method of places,” involves associating facts to be memorized with real or imagined spatial locations. The method was known to the ancient Greeks. Matteo Ricci, a Jesuit in China, thought this was one of the most valuable things he could teach the Chinese. A modern introduction is Moonwalking with Einstein: The Art and Science of Remembering Everything.

Lynne Kelly is a scholar who argues that the transmission of large bodies of cultural information by the method of places played a central role in many non-literate societies. In traditional aboriginal Australia, the landscape was not just a collection of physical sites and associated ecological resources, but was tagged with a large body of information. Walking through the landscape, in reality or in imagination, would call forth the associated facts. At least for someone in the know. Knowledge was power.  Multiple stages of initiation passed on the carefully guarded stories and knowledge associated with particular places and paths. Some of this information was about mythology and social organization, some of it was practical knowledge of the environment, well beyond what any one individual could discover in a lifetime.

Kelly also argues that in more stratified (but still non-literate) societies, people were not just tagging the landscape with facts to be remembered, but were building substantial monuments to encode important information. She makes a case that the megaliths of Neolithic Europe, and Stonehenge in its initial stages, were memory palaces, built at the behest of knowledge elites, whose social position depended on their monopolizing a store of encyclopedic information.

She makes her argument here and here.

Little deuce coupe, a prehistory

Wheels probably started being used by copper miners in southeastern Europe, in the Carpathians, in the 4^th millennium BC. The early wheels were wheelsets, with the wheel fixed solidly to an axle, and the axle rotating. For miners, any alternative to carrying loads of ore on their backs must have been welcome. Miners can smooth a path for their carts, so the problem of moving wheels on uneven terrain is reduced.

Several centuries later, somewhere between the Carpathians and the steppe country north of the Black Sea, another kind of wheel was developed, with the wheel rotating freely around a fixed axle. The new wheel was perfectly suited to a new way of life that developed on the steppes, where nomads followed herds of livestock. Horses might have been the flashiest part of the new lifestyle, but oxcarts, carrying family belongings from one grazing site to another, may have been just as important.

Judging by their reconstructed vocabulary, speakers of Proto-Indo-European – the ancestor of most of the languages of Europe and Northern India – were among those adopting the new technology.

(Actually, looking at the reconstructions, it looks like the adoption of the wheel may have come after Proto-Anatolian – ancestor to Hittite – had branched off from other Indo-European languages.)

Some cultures got into wheels more than others. Sub-Saharan African societies, even including cattle nomads, never adopted the wheel. In the Middle East, wheeled vehicles gave way pack camels sometime between Roman times and the Islamic period. As a result, Islamic states didn’t have to put as much effort into road building as earlier states, and the narrow crooked streets of Muslim-era cities were made for camels, not carts, to traverse. Wheeled transportation was limited in Japan. And in the New World, wheels are known only from children’s toys.

Things were different in Europe and its cultural offshoots, where wheeled vehicles have exercised a hold on the imagination – especially the male imagination – right up to the present. This is from Richard Bulliet’s recent book, The Wheel: Inventions and Reinventions (p. 33):

Not only is the world racing fraternity composed almost entirely of men, but it has historically recruited very few drivers from East Asia, South Asia, the Middle East and Africa. …[T]he five-thousand-year history of wheels in Indo-European societies – specifically in Europe, including its former colonies, and North America – testifies to an affinity between vehicle driving and male identity in cultures that descend from the Proto-Indo-European linguistic tradition. Since the earliest days of wagon nomads and chariots, through the carriage revolution of the sixteenth century, and down to the automobile era, men brought up in European (and Euro-American) societies have repeatedly linked their manhood to their vehicles.

And here are the Beach Boys, carrying on the tradition in Little Deuce Coupe.

Jomon

We celebrated the evolution of the first flowers on Amborella Day, March 17. Now we can finally celebrate people having pots to put flowers in. The earliest pots in the world come from the Jomon culture in Japan. (Although they were more for cooking and storage than for flower arranging, of course.)

The advent of pottery defines the beginning of the Neolithic (New Stone Age). In some places, the Neolithic coincides with the inception of agriculture. But not everywhere. The Jomon are hunter-gatherers, ancestors to Japan’s Ainu. They live in villages, harvesting marine and arboreal resources (e.g. shellfish and acorns), which are rich enough that they can settle down and develop an increasingly elaborate ceramic tradition. A pot like this one was not thrown on a wheel, but made by hand, from coils of clay. Jomon means “cord marked,” from the patterns marked on the pots with cords.

Quest for fire, or, Eisenhower steak

833 – 789 thousand years ago

This post, and some subsequent tweets, are a few days late. I was touring wineries in the Sunnyslope region of Idaho, a little ways outside Boise. Recommended, if you get a chance; you could pick up some wines that would pair well with Eisenhower steak (recipe below).

On June 3 on Logarithmic History, our ancestors had gotten as far as steak tartare. Now it’s time for an Eisenhower steak (cooked directly on the coals; see below).

What really distinguishes humans from other animals? We’ve covered some of the answers already, and will cover more in posts to come. But certainly one of the great human distinctions is that we alone use fire. Fire is recognized as something special not just by scientists, but in the many myths about how humans acquired fire. (It ain’t just Prometheus.) Claude Lévi-Strauss got a whole book out of analyzing South American Indian myths of how the distinction between raw and cooked separates nature from culture. (I admit this is where I get bogged down on Lévi-Strauss.)

Until recently the story about fire was that it came late, toward the latter days of Homo erectus. But Richard Wrangham, a primatologist at Harvard, turned this around with his book Catching Fire (which is not the same as this book), arguing that the taming of fire goes back much earlier, to the origin of Homo erectus. Wrangham argues that it was cooking in particular that set us on the road to humanity. Cooking allows human beings to extract much more of energy from foods (in addition to killing parasites). Homo erectus had smaller teeth and jaw than earlier hominins and probably a smaller gut, and it may have been fire that made this possible. Cooking is also likely to have affected social life, by focusing eating and socializing around a central place. (E O Wilson thinks that home sites favored intense sociality in both social insects and humans.)

Surviving on raw food is difficult for people in a modern high-tech environment and probably impossible for people in traditional settings. Anthropologists are always looking for human universals, and almost always finding exceptions (e.g. the vast majority of societies avoid regular brother-sister marriage, but there are a few exceptions, including Roman Egypt and Zoroastrian Iran). But cooking seems to be a real, true universal. No society is known where people got by without cooking. Tasmanians, isolated from the rest of the world for 10,000 years, with the simplest technology of any people in recent history, had supposedly lost the art of making fire, but still kept fires going and still cooked.

Recent archeological finds have pushed the date for controlled use of fire back to 1 million years ago, but not all the way back to the origin of Homo erectus. This doesn’t mean Wrangham is wrong. Fire sites don’t always preserve very well: we have virtually no archeological evidence of the first Americans controlling fire, but nobody doubts they were doing it. It could be that it will be the geneticists who will settle this one. The Maillard (or browning) reaction that gives cooked meat much of its flavor generates compounds that are toxic to many mammals but not (or not so much) to us. At some point we may learn just how far back genetic adaptations to eating cooked food go.

An alternative to an early date for fire, there is the recent theory that processing food, by chopping it up and mashing it with stone tools, was the crucial early adaptation.

Whenever it is exactly that humans started cooking, the date falls in (Northern hemisphere) grilling season on Logarithmic History, so you can celebrate the taming of fire accordingly. It doesn’t have to be meat you grill. Some anthropologists think cooking veggies was even more important. I recommend sliced eggplant particularly, brushed with olive oil to keep it from sticking, and with salt, pepper, and any other spices.

On the other hand, Homo erectus probably appreciated a good Eisenhower steak, cooked directly on the coals. (Yes, this actually works pretty well.)

Eisenhower Coal-Fired Steak

Named for the 34th president of the United States, who liked to cook his steaks directly on the coals, this preparation will create a crunchy, charred exterior with rosy, medium-rare meat inside.

Lump hardwood coals work better than briquettes for this recipe because they burn hotter. Be sure you use long-handled tongs. (Sorry, this method is for charcoal or wood grilling only.)

You might find an uneven exterior crust, especially when using lump charcoal, because it is irregularly shaped (unlike the uniform briquette pillows). If that happens, try to position the steak so that it is more directly on the coals and gets an even char. Clasp the steak in the tongs and rap the tongs against the edge of the grill to knock off the occasional clinging ember. If you have some ash, flick it off with a pastry brush.

Make Ahead: The steaks can be seasoned and refrigerated up to 4 hours in advance. Bring them to room temperature before they go on the fire.

INGREDIENTS

• 1 teaspoon olive oil
• Two 1 1/2-inch-thick boneless rib-eye steaks (about 28 ounces total)
• 2 teaspoons coarse sea salt
• 2 teaspoons freshly cracked black pepper

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DIRECTIONS

Prepare the grill for direct heat. Light the charcoal; when the coals are just covered in gray ash, distribute them evenly over the cooking area. For a hot fire (450 to 500 degrees), you should be able to hold your hand about 6 inches above the coals for 2 or 3 seconds. Have a spray water bottle at hand for taming any flames. But use it lightly; you don’t want to dampen the heat too much, and some flames here are fine.

Meanwhile, brush the oil on the both sides of the steaks, then season both sides liberally with salt and pepper.

Once the coals are ready, place the steaks directly on the coals (see headnote). Cook, uncovered, for 6 minutes on one side, then use tongs to turn them over. Cook for about 5 minutes on the second side.

Transfer the steaks to a platter to rest for 10 minutes. Serve as is, or cut them into 1/2-inch-thick slices.