evolution's third replicator?

New Scientist | Last year Google announced that the web had passed the trillion mark, with more than 1,000,000,000,000 unique URLs. Many countries now have nearly as many computers as people, and if you count phones and other connected gadgets they far outnumber people. Even if we all spent all day reading this stuff it would expand faster than we could keep up.

Billions of years ago, free-living bacteria are thought to have become incorporated into living cells as energy-providing mitochondria. Both sides benefited from the deal. Perhaps the same is happening to us now. The growing web of machines we let loose needs us to run the power stations, build the factories that make the computers, and repair things when they go wrong - and will do for some time yet. In return we get entertainment, tedious tasks done for us, facts at the click of a mouse and as much communication as we can ask for. It's a deal we are not likely to turn down.

Yet this shift to a new replicator may be a dangerous tipping point. Our ancestors could have killed themselves off with their large brains and dangerous memes, but they pulled through. This time the danger is to the whole planet. Gadgets like phones and PCs are already using 15 per cent of household power and rising (New Scientist, 23 May, p 17); the web is using over 5 per cent of the world's entire power and rising. We blame ourselves for climate change and resource depletion, but perhaps we should blame this new evolutionary process that is greedy, selfish and utterly blind to the consequences of its own expansion. We at least have the advantage that we can understand what is happening. That must be the first step towards working out what, if anything, to do about it.

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Susan Blackmore is becoming more and more interesting with the passage of time.

oh lawd....,

teabagger redux?

Politico | Screaming constituents, protesters dragged out by the cops, congressmen fearful for their safety — welcome to the new town-hall-style meeting, the once-staid forum that is rapidly turning into a house of horrors for members of Congress.

On the eve of the August recess, members are reporting meetings that have gone terribly awry, marked by angry, sign-carrying mobs and disruptive behavior. In at least one case, a congressman has stopped holding town hall events because the situation has spiraled so far out of control.

“I had felt they would be pointless,” Rep. Tim Bishop (D-N.Y.) told POLITICO, referring to his recent decision to suspend the events in his Long Island district. “There is no point in meeting with my constituents and [to] listen to them and have them listen to you if what is basically an unruly mob prevents you from having an intelligent conversation.”

In Bishop’s case, his decision came on the heels of a June 22 event he held in Setauket, N.Y., in which protesters dominated the meeting by shouting criticisms at the congressman for his positions on energy policy, health care and the bailout of the auto industry.

Within an hour of the disruption, police were called in to escort the 59-year-old Democrat — who has held more than 100 town hall meetings since he was elected in 2002 — to his car safely.

the shale revolution

Nature | The vast reserves of US natural gas must be used judiciously to ease the transition to clean energy.

Several years ago, it looked as though the United States was running short of natural gas. Prices spiked as declining production in old fields collided with increasing industrial demand. Electric utilities shifted from 'clean' gas back to cheap coal, and suppliers began building terminals to import liquefied natural gas from abroad. Yet today, coal-fired power is again on the wane, ports for liquefied natural gas are idling below capacity, and the nation is awash with gas.

So what happened? Clearly, the threat of carbon regulation has curbed industry's appetite for coal, and the sagging economy has depressed energy demand across the board. But just as importantly, natural-gas production is again on the rise. Thanks to advances in drilling technology, including horizontal drilling and more effective rock fracturing, producers have at last unlocked the vast quantities of gas trapped underground in impermeable strata of shale.

The Potential Gas Committee, a volunteer group of industry, government and academic experts headquartered in Golden, Colorado, increased its estimate of recoverable gas reserves by 39% in its biennial report released last month, mostly because of shale gas. The new total, almost 60 trillion cubic metres, is equivalent to about a century's worth of gas at current usage rates.

Policy-makers everywhere should take note. Shale formations similar to those that have upended the US natural-gas market exist all over the world. Early explorations are already under way in Canada and several European countries, many of which are overly reliant on coal and politically risky Russian gas imports. And there is no reason to think the development will stop there.

living in tents, by rules, under a bridge

NYTimes | The chief emerges from his tent to face the leaden morning light. It had been a rare, rough night in his homeless Brigadoon: a boozy brawl, the wielding of a knife taped to a stick. But the community handled it, he says with pride, his day’s first cigar already aglow.

By community he means 80 or so people living in tents on a spit of state land beside the dusky Providence River: Camp Runamuck, no certain address, downtown Providence.

Because the two men in the fight had violated the community’s written compact, they were escorted off the camp, away from the protection of an abandoned overpass. One was told we’ll discuss this in the morning; the other was voted off the island, his knife tossed into the river, his tent taken down.

The chief flicks his spent cigar into that same river. There is talk of rain tonight.

Behind him, the camp stirs. Other tent cities have sprung up recently around the country, but Rhode Island officials have never seen anything like this. A tea kettle sings.

A heavily pierced young person walks by without picking up an empty plastic bottle, flouting the camp compact that says everyone will share in the labor. The compact may be as impermanent as this sudden community by the river, but for now it is binding. The chief speaks, the bottle is picked up.

The chief, John Freitas, is 55, with a gray beard touched by tobacco rust. He did prison time decades ago, worked for years as a factory supervisor, then became homeless for all the familiar, complicated reasons.

why YOU come here....,

Physorg | New research demonstrates that single neurons in the reward center of the brain process not only primitive rewards but also more abstract, cognitive rewards related to the quest for information about the future. The study, published by Cell Press in the July 16 issue of the journal Neuron, enhances our understanding of learning and suggests that current theories of reward should be revised to include the effect of information seeking.

"The desire to know what the future holds is a powerful motivator in everyday life, but we know little about how this desire is created by neurons in the brain," says lead study author Dr. Ethan S. Bromberg-Martin from the National Institutes of Health in Bethesda, Maryland. Dr. Bromberg-Martin and coauthor, Dr. Okihide Hikosaka, investigated whether dopamine-releasing neurons associated with processing basic primitive rewards, such as food and water, are also involved in processing more abstract rewards.

The researchers focused on a form of cognitive reward that involves anticipation of a substantial future gain. Specifically, people (and animals) do not like to be held in suspense and prefer to receive advance information about the rewards they will receive in the future. In this study, a simple decision task allowed rhesus monkeys to choose whether to view informative pictures that would tell them the size of upcoming water rewards. The researchers recorded the activity of dopamine reward neurons while the monkeys performed the task.

The monkeys showed a strong preference for information about upcoming rewards and preferred to receive the information as soon as possible, even though the information had no effect on the final reward outcome. Importantly, the dopamine neurons that signaled the monkey's expectation of water rewards also signaled the expectation of advance information in a manner that was correlated with the strength of the animal's preference. "The monkeys and dopamine neurons treated information about rewards as if it was a reward itself," explains Dr. Bromberg-Martin.

old population surpasses young

Guardian | The world is about to cross a demographic landmark of huge social and economic importance, with the proportion of the global population 65 and over set to outnumber children under five for the first time.

A new report by the US census bureau highlights a huge shift towards not just an ageing but an old population, with formidable consequences for rich and poor nations alike. The transformation carries with it challenges for families and policymakers, ranging from how to care for older people living alone to how to pay for unprecedented numbers of pensioners – more than 1 billion of them by 2040.

The report, An Ageing World: 2008, shows that within 10 years older people will outnumber children for the first time. It forecasts that over the next 30 years the number of over-65s is expected to almost double, from 506 million in 2008 to 1.3 billion – a leap from 7% of the world's population to 14%. Already, the number of people in the world 65 and over is increasing at an average of 870,000 each month.

oil speculation limits weighed

Washington Post | Federal regulators moved closer on Tuesday to issuing new rules to limit oil speculation, addressing concerns that Wall Street firms may have manipulated the price of oil through financial trading.

The Commodity Futures Trading Commission held the first of three hearings to explore ways to keep financial firms from amassing such large positions in energy markets that they have outsized power to affect prices.

"I believe that at the core of our mission is to make sure that the markets are fair and orderly," CFTC Chairman Gary Gensler said in an interview after the hearing. "It's really central to every American -- from how much you spend for gas at the pump to your heating costs in the wintertime."

Concerns that speculators were influencing oil prices bubbled up last summer when the price of a barrel of oil spiked to an all-time high. At the time, the CFTC leadership was not interested in pursuing new regulations to limit speculation. And the agency issued a controversial report suggesting that the rising oil prices were the result of natural factors of supply and demand.

Gensler, who became chairman in May, has said he thinks speculators have helped to boost the price of oil. In the interview, he said he hopes that his agency could officially propose new rules in the fall to govern energy speculation. The price of oil has increased by about 50 percent this year.

One factor that may play into the debate is a report the CFTC is scheduled to release next month about the types of firms, such as banks and hedge funds, that hold big positions in energy investments. CFTC officials said the report, which will be updated periodically, is not expected to cast judgment on whether speculation is influencing oil prices. If, however, it shows that few players dominate the market, the information could be used by those who support curbs on oil speculation.

Greenpeace study finds oil companies may be doomed

Guardian | Environmental activist network argues that the oil industry might be approaching a tipping point from fall in the price, advances in technology and policies on climate change

A long-term decline in the demand for oil could undermine the huge investments in Canadian tar sands, which have been heavily opposed by environmentalists, according to a report published today.

The report, by Greenpeace, will make uncomfortable reading for the companies that are investing tens of billions of pounds to exploit the hard-to-extract oil in the belief that demand and the price would climb inexorably as countries such as China and India industrialise.

Citing projections from the oil producers' cartel Opec and the International Energy Agency, as well as various oil experts, the report casts doubt on the conventional assumption that consumption and prices will begin gathering pace once the world pulls itself out of recession.

It argues that alongside the cyclical fall in the oil price there are more fundamental structural changes taking place. These are driven by advances in energy efficiency and alternative energy, cleaner vehicles, government policies on climate change and concerns over energy security. Greenpeace has posted the report to 200 shareholders in Shell and BP, including pension funds, in an effort to put pressure on the companies to think again. BP reports quarterly results tomorrow and Shell on Thursday.

Lorne Stockman, the author of the report, said: "A peak in oil demand was barely discussed even a year ago, but now it is a viable idea. When it happens, I wouldn't want to guess, but it will happen sooner than we thought. There has been lots of talk about a supply peak, but it is good to start talking about a demand peak, and that has huge implications for these companies.

"All of the international oil companies as you look beyond 2020 need a high oil price to be profitable, because they are increasingly being pushed to develop expensive resources in not just the tar sands, but in deep water and offshore Arctic sites.

"But there is something more structural going on," he added. "Governments are beginning to act, and not just the Obama administration. In the EU, the policy driver is climate change, and in China and the US, it is about energy security and the vulnerability of the economy to volatility in the oil price."

opec braces for sharp drop in oil prices

BloggingStocks | Why is OPEC expecting a sharp drop in oil prices? First, much of the rise in oil prices has followed the rally on Wall Street. Investors reasoned that higher stock prices means that business is doing better and hence a need for more oil, and prices rise.

Not so fast. Business demand for oil is weak, and the consumer got clobbered by the recession and is holding back spending money. So the classic relationship between the stock market and oil that investors follow is not there this year.

The Wall Street Journal is reporting that stockpiles are at a 24-year high. Distillate demand for gasoline and diesel fuel dropped by 15%. Refiners have cut back production to 85.8%, from 87.9% the previous week. Distillate stocks surged to 160.5 million barrels, the highest level since 1985.

The price of September crude closed at $68.05 per barrel on Friday, up 89 cents. The futures contracts for crude in are a contango. What is a contango? It is a futures market where the prices for distant contracts are higher that those for nearby delivery. For example, the September futures contract closed at $68.05 per barrel while the December contract closed at $72.52 per barrel. This sets up a huge profit margin for oil traders. They simply buy the cash crude oil and sell distant futures contracts against them. The profit spread between September and December is $4.47 per barrel. Figure that profit on say 1,000,000 barrels.

The effect of these factors are that the buyers of nearby oil have no more room to store it. They are using tankers and barges and running out of room. So now we have a glut of oil. OPEC sees this and is bracing for a sharp drop in prices.

This is also how banks are racking up huge profits. They are borrowing money at 0.25% from the Fed and lending it out longer term at much higher rates to businesses and consumers.

Would you sell oil contracts at these levels?

more grain, fewer nutrients

Farmonline | SINCE the Green Revolution of the 1960s, the world has produced a lot more grain—but there may be a lot less in it, a unique experiment in the United Kingdom has revealed.

Recent analysis of 160 years of crop samples from Rothamsted Research Station near London discovered that levels of essential micronutrients remained consistent in wheat grain from 1844 to the late 1960s, but then began a decline that continues to this day.

The nutrient decline began when traditional long-straw wheat varieties where phased out in favour of higher-yielding semi-dwarf varieties.

As wheat plants have grown smaller since the 1960s, grain nutrient density has continued to decrease.

Compared to the old long-straw varieties, Rothamsted’s modern dwarf wheat grain carries on average 20-30 per cent less zinc, iron, copper and magnesium.

For zinc, a critical human nutrient, the decline is even more pronounced if the most recent five years of data are compared, with average nutrient levels in wheat harvested from 1844-1967.

the new reality

Fist tap Dale for making me aware of Loretta Napoleoni

u.s. government completely out of wheat

Barternews | Quietly, the last of the U.S. government’s wheat reserves, held in the Bill Emerson Humanitarian Trust, were sold in late May onto the domestic market for cash. The cash was put in a trust for food aid. With no other government wheat holdings, U.S. government wheat stocks are now totally exhausted.

The following recent statements by Rebecca Bratter, director of policy for U.S. Wheat Associates, provides insights:

“While the U.S. wheat industry strongly supports the administration’s goal of maintaining current food aid programs to prevent rampant hunger worldwide, there is concern regarding the impact of selling reserve wheat on the domestic market and over the lack of commitment from the administration to replenish the Bill Emerson Humanitarian Trust.

“U.S. Wheat Associates has shared these concerns with high officials at USDA and on the President’s staff and has asked about the Administration’s intent regarding replenishment of the Bill Emerson Humanitarian Trust. Staff from the office of the President’s Special Agricultural Assistant noted that while there is no commitment at this time, the administration intends to replenish the Trust once the supply and price scenario stabilizes.”

(Note: U.S. Wheat Associates works in 90 countries promoting U.S. wheat exports.)

The Bill Emerson Humanitarian Trust was established in 1980 by an act of Congress and is authorized to hold up to 4 million metric tons of wheat, corn, sorghum and rice, as a reserve for global food crises. The wheat is purchased and managed by the Commodity Credit Corporation and included in the total amount of wheat owned and held by the U.S. government. Holdings by the BEH Trust for corn, sorghum and rice are also zero.

For the decade of the ‘80s, government wheat holdings (including those in the BEH Trust) averaged 358 million bushels. For the decade of the ‘90s, government wheat holdings averaged 133 million bushels. Since 2000, government wheat holdings dropped steadily until recently when the last of the government-owned wheat was sold.

With no formal plan for wheat stocks by the U.S. government, wheat stocks have defaulted to the arena of the private free-market sector. Unfortunately, the private sector has no plans for any kind of minimum wheat stocks that would protect the American public from a price and/or availability standpoint.

Private wheat stocks are divided into two major categories — on-farm wheat stocks owned by farmers, and off-farm wheat stocks owned by warehouses and grain companies. These two together held 305.6 million bushels of wheat as of June 1 (or roughly 1 bushel per person living in the United States) the lowest level in 60 years.

Of these stocks, on-farm wheat stocks are at 25.6 million bushels, the lowest level of on-farm wheat stocks since the USDA started keeping tabs back in 1934. So as you are driving in rural America before wheat harvest, the farmer’s bins have never been so empty.

The USDA, projects America to have a bumper wheat crop in 2008, producing 2.43 billion bushels and consuming and exporting 2.30 billion bushels. This leaves a meager 133 million bushels (5.5 percent of production) as a margin for error. Globally, the USDA projects wheat production to be 24.36 billion bushels, consumption to be 23.74 billion bushels for a relatively smaller margin of 622 million bushels or 2.6% of production.

The recent wheat crises in America was sparked by the nation exporting more wheat than it produced. This means the true 2008 wheat margin for Americans is really the global margin of 2.6%. Any decline from global projections could precipitate greater wheat exports from America and further draw down already low domestic and global wheat stocks.

Food security is emerging as a global focal point. With the U.S. government and the private sector lacking visions for stocks, food security is poised to grow as a grass-roots issue around the nation.

political, social, and economic forecast

Interesting analysis, channel, and video series.

charlie gibson's "the truth about oil"

ABC | From the trail of oil pipelines snaking through Oklahoma to the middle of the Gulf of Mexico, Gibson crisscrossed the country in search of the answer to one salient question -- what is the true cost of oil? He reports from Cushing, Oklahoma, a remote outpost where the price of a barrel of oil there dictates the price nationally. He travels 160 miles off the coast of Louisiana to see one of the deepest drilling oil rigs in America and visits "refinery row" along the Gulf Coast, where a third of America's oil refineries are concentrated.

Despite talk of dwindling oil reserves, new technologies have vastly increased the amount of oil, providing a larger reserve today than a decade ago. Last summer's $147 a barrel price baffled many Americans, but Wall Street insiders tell Gibson that speculators caused the price to skyrocket.

Americans consume a quarter of the world's oil, yet make up only 3 percent of the global population. When confronted by Gibson, Energy Secretary Steven Chu admits "we're headed for a train wreck." Chu explains how a new generation of biofuels could help the U.S. decrease its dependence on foreign oil. In addition to interviews with dozens of experts and industry leaders, Gibson also sat down with General Wesley Clark, the former NATO commander who discussed the role that oil played in the Iraq war.

softening you up for the goldman frontrunning fiasco

NYTimes | Traders Profit With Computers Set at High Speed - It is the hot new thing on Wall Street, a way for a handful of traders to master the stock market, peek at investors’ orders and, critics say, even subtly manipulate share prices.

It is called high-frequency trading — and it is suddenly one of the most talked-about and mysterious forces in the markets.

Powerful computers, some housed right next to the machines that drive marketplaces like the New York Stock Exchange, enable high-frequency traders to transmit millions of orders at lightning speed and, their detractors contend, reap billions at everyone else’s expense.

These systems are so fast they can outsmart or outrun other investors, humans and computers alike. And after growing in the shadows for years, they are generating lots of talk.

Nearly everyone on Wall Street is wondering how hedge funds and large banks like Goldman Sachs are making so much money so soon after the financial system nearly collapsed. High-frequency trading is one answer.

And when a former Goldman Sachs programmer was accused this month of stealing secret computer codes — software that a federal prosecutor said could “manipulate markets in unfair ways” — it only added to the mystery. Goldman acknowledges that it profits from high-frequency trading, but disputes that it has an unfair advantage.

Yet high-frequency specialists clearly have an edge over typical traders, let alone ordinary investors. The Securities and Exchange Commission says it is examining certain aspects of the strategy.

“This is where all the money is getting made,” said William H. Donaldson, former chairman and chief executive of the New York Stock Exchange and today an adviser to a big hedge fund. “If an individual investor doesn’t have the means to keep up, they’re at a huge disadvantage.”

detroit - the post-apocalyptic future of american cities

AlMartinRaw | Last week I had a chance to talk to a friend who just got back from Detroit and boy did he get an eyeful of America’s Future. After listening to him describe Detroit , it’s obvious that it has all fallen apart. First of all, there’s very little civil authority or regular civil government remaining and in operation. Almost everything has been turned over to these so-called Private Management Companies. And this is how it’s being done. They block out areas, in which 80% or more of the houses have been foreclosed on, which happens to be almost the entire city and county. They have selectively begun to bulldoze the properties which have been foreclosed on. The rest have been boarded up. Then they have turned over management of these 100 block area to private companies which have become defacto governments. They have the literal authority of “governments” and they’re paid a flat fee from the city, county or state to “manage,” as they say, a square block of this urban wasteland.

These Private Management Companies sell themselves as residual property management firms. Most of these companies, as it turns out, are in fact off-shore subsidiaries of Private Military Contractors (PMCs). They provide a catchall service. In other words, they regulate how much electrical power and natural gas flows through these areas. They also act as police force, and they act as management for local civil government.

However this Urban Wasteland Management has been pretty efficient. They want to protect what remaining wealthy areas that still exist, like Bloomfield Hills. These companies come in and effectively build large barbed wire fences, around these mostly abandoned square block areas. Some people are still living in them, by the way, even though most of them are boarded up because they’re no longer bothering to serve process through the entire foreclosure procedure. Oftentimes once the house has been taken back and is ultimately owned by the city or county or some government, they let the people stay there until it’s abandoned and then taken over by squatters. Then they’re given a 72 hour notice to leave, by this private management company – before they come in and bulldoze the house. If you’re not out, that’s it. The bulldozers run. They can bulldoze the place with you in it – with legal impunity.

the guardian institutions of hierarchy

paulchefurka | One aspect of human culture that seems irresistible to the ancient status-seeking part of our brain is the development of hierarchies. The encoding of personal status and power into social structures is evident in the tribes and troops of all the great apes, but human beings have gone much further. We built an entire globe-spanning civilization on the foundation of hierarchy.

One inevitable effect of social hierarchies (in fact the effect that made our global civilization possible) is the consolidation of power. As new power comes into a hierarchic social system it flows preferentially to the top. As the system develops, even the small amount of power available to those at the bottom of the social pyramid is removed and ends up concentrated at the top in a power elite. This becomes a positive feedback loop: the more power is consolidated at the top, the easier the consolidation becomes.

This consolidation of power is seen in all social hierarchies. As you would expect, our most hierarchic societies, from ancient Egypt to Stalinist Russia to the USA, exhibit it most profoundly.

You can think of this effect as a form of social reverse osmosis, in which power is pumped through a semi-permeable membrane up a gradient from social regions of low power concentration to regions of high concentration, with class boundaries forming the membrane between them.

Physical reverse osmosis requires both a semi-permeable membrane and a pump, so it's logical to look for similar mechanisms in this social metaphor. What drives social power from low to high concentrations? And what keeps the semi-permeable membrane of social class boundaries intact so that the whole system can function?

In our metaphor of reverse osmosis, these mechanisms are provided by what I call the Guardian Institutions. These are the corporate, economic, financial, political, legal, religious, educational and communications institutions that form the structural skeleton of our civilization.

iPS cells yield live mice

The Scientist | Researchers have created live mice from induced pluripotent stem (iPS) cell lines, demonstrating iPS cells are as pluripotent as embryonic stem (ES) cells, according to two studies published online today.

"This ability to make a mouse from the cells of a Petri dish is the most stringent standard that mouse embryonic cells are held to, and iPS cells now meet that standard, which has been a lingering doubt," said stem cell biologist George Daley of the Harvard Stem Cell Institute and Children's Hospital Boston, who was not involved in the work. "It assures us that iPS cells can do all the things that ES cells can do."

subreality mainstreamed?

NYTimes | This week, the 40th anniversary of the first moon landing, there’s much talk of exploring other worlds. Which is exciting and grand; such is the stuff that dreams are made on. Yet we don’t need to go abroad to find amazing new life forms. We just need to look at the palms of our hands, the tips of our fingers, the contents of our guts.

The typical human is home to a vast array of microbes. If you were to count them, you’d find that microbial cells outnumber your own by a factor of 10. On a cell-by-cell basis, then, you are only 10 percent human. For the rest, you are microbial. (Why don’t you see this when you look in the mirror? Because most of the microbes are bacteria, and bacterial cells are generally much smaller than animal cells. They may make up 90 percent of the cells, but they’re not 90 percent of your bulk.)

This much has been known for a long time. Yet it’s only now, with the revolution in biotechnology, that we’re able to do detailed studies of which microbes are there, which genes they have, and what they’re doing. We’re just at the start, and there are far more questions than answers. But already, the results are astonishing, and the implications profound.

Even on your skin, the diversity of bacteria is prodigious. If you were to have your hands sampled, you’d probably find that each fingertip has a distinct set of residents; your palms probably also differ markedly from each other, each home to more than 150 species, but with fewer than 20 percent of the species the same. And if you’re a woman, odds are you’ll have more species than the man next to you. Why should this be? So far, no one knows.

But it’s the bacteria in the digestive tract, especially the gut, that intrigue me most. Many of these appear to be true symbionts: they have evolved to live in guts and (as far as we know) are not found elsewhere. In providing their habitat — a constant temperature, some protection from hostile lifeforms and regular influxes of food — we are as essential to them as they are to us.

And they definitely are essential to us. Gut bacteria play crucial roles in digesting food and modulating the immune system. They make small molecules that we need in order for our enzymes to work properly. They interact with us, altering which of our genes get turned on and off in cells in the intestinal walls. Some evidence suggests that they are essential for the building of a normal heart. Finally, it seems likely that gut bacteria will turn out to affect appetite, as well as other aspects of our behavior, though no one has shown this yet. (Imagine the plea: I’m sorry, sir, my microbes made me do it.)

Together, your gut microbes provide you with a pool of genes far larger than that found in the human genome. Indeed, the gut “microbiome,” as it is known, is thought to contain at least 100 times more genes than the human genome. Moreover, whereas humans are extremely similar to one another at the level of the genome, the microbiome appears to differ markedly from one person to the next.

What determines these differences? Good question. Diet has some effect: a diet rich in sugars and fats reduces the diversity of gut bacteria, and shifts the balance towards those that are more efficient at extracting energy. Start eating more plants and you can shift the balance back, and increase the diversity of your gut microbes. Your own genetic background may play a role as well, though we are far from understanding how, or how much. It probably also matters which other microbes are present: as in any ecosystem, relationships among different inhabitants are likely to be complex.

(At this point, I’d like to introduce a caveat. We know that the diversity of microbial species differs between your gut and mine, and that the less related we are, the more that will be true. Family members tend to have more similar gut microbes than nonrelatives, and preliminary evidence suggests that geography matters, too. So the gut microbes of people in China are different from those of people in the United States — though whether this is due to diet, human genes or geography is entirely unknown. But despite this variation at the species level, we don’t yet know how much variation there is at the genetic level. It may be that different sets of gut microbes provide broadly equivalent sets of genes.)

Naturally, a huge effort is now under way to see whether differences in gut bacteria are responsible for differences in health. But what interests me most about all this is that it suggests another mode of human evolution. Bacteria evolve quickly: they can go through many thousands of generations for every human one.

This has two potential consequences. First, during your lifetime, your bacteria can change their genes even though you cannot change yours. (You do have some flexibility: your immune system has a built-in capacity to change.) It may be that gut bacteria evolve in response to short-term changes in the environment, especially exposure to food-borne diseases. They may thus act as an evolving supplement to the immune system.

The second potential consequence is further reaching. Because bacteria can evolve so fast, it may be that some of what we think of as human evolution — like the ability to digest new diets that accompanied the invention of agriculture — is actually bacterial evolution. We know that hostile bacteria — those that cause diseases in ourselves and our domestic plants and animals — have undergone dramatic genetic changes in the last 10,000 years. Perhaps our friendly bacteria have, too.