The scientific luminary Lynn Margulis, an outspoken pioneer in evolutionary biology, died on 24^th November, in Amherst, Massachusetts, aged 73. Renowned for a radical theory of the origin of complex cells, her death marks the loss of a unique and contrarian voice in biology, and the closing of a vibrant and spirited life.

I was fortunate to meet Prof. Margulis in Oxford last year, in an impromptu and surprising encounter. “Is that… the Lynn Margulis,” a friend had said, peering incredulously at a seminar listings noticeboard, “Why has nobody told us about this?” Ten minutes of frantic sprinting later, we slipped into a seminar room on South Parks Road. The audience numbered roughly six.

“You’re here for Lynn?” somebody asked warmly, and then added, “We’ll have to wait a second or two. We know she’s here somewhere, but the thing about Lynn is she keeps you guessing.”

Lynn Margulis has had people guessing for decades. Her provocative hypotheses – generated at almost improbable rates – have engrossed and outraged the scientific establishment for forty years. She brought to evolutionary biology the expansive, daringly playful imagination of a poet or playwright, unafraid to dream up eccentric and spirited plots for a cast of outlandish characters, and ask nature, puckishly, if it had had similar thoughts. It is a testament to her scientific intuition that some of the time it had.

Margulian endosymbiosis, as it is known, remains one of the most beguilingly wonderful ideas in modern science, and its eponymous discoverer deserves a place amongst the pantheon of scientific pioneers. At the cellular level, eukaryotic life – essentially everything besides bacteria and viruses – has long entranced biologists: in all its sublime complexity, the eukaryotic cell has an aura of extraordinary mystique. It shimmers with a bewitching intricacy, an elaborate biomolecular marionette fashioned by aeons of evolutionary ingenuity. Margulis’s astonishing vision lay in seeing that this integrated whole, the quintessence of biological cohesion, had its origins in disparate, independent, elemental entities, joined in a marriage of convenience somewhere in the meandering backwaters of deep time. In essence, a bacterium found itself inside a larger cell, and, remarkably, stayed for posterity. Its descendants are within us all today; indeed, they part of us. We are, in a spectacular sense, part bacterial.

Audaciously resuscitating an obscure and maligned tradition stretching back to the 1880s, Margulis’s insight was a virtuoso and rebellious move, but also – it was felt at the time – an outrageous affront to biological sanity. Across the subsequent decades, she acquired a contrarian reputation, and came to see herself as a dissident voice in a science contaminated by ideological convictions. She was apt to dismiss canonical neo-Darwinian results as crude, capitalist misreadings of evolutionary history; for her, biology’s ongoing love-affair with microeconomics was a disturbing and unsustainable fling, dangerously one-dimensional and inevitably destined to self-combust.

Her instinctive aversion to the Machiavellian mood of modern biology, then, grew from a sense that cooperation in nature was a ubiquitous and powerful driver of innovation, and she did not shy from offering broad cultural diagnoses for her colleagues’ obstinacy: their commitment to monophyly (having a single ancestor) was nothing more than the latent misfiring of monotheistic and monarchical inclinations, and the resistance to accepting symbiosis as a driving force for evolutionary novelty grew from a fear of its “female” connotations. The world as she saw it cannot be meaningfully fragmented, and she warmed naturally and famously to Lovelock’s Gaia hypothesis: the Earth is a vast and indissoluble community, immune to the atomising tendency of “feudal” science.

Margulis was admitted to the University of Chicago aged 14, after a difficult childhood under insensitive parents. Two years later, she fell in love with Carl Sagan, whom she married before the age of 20. She found in biology a quiet, contemplative, aesthetic privacy, seeing “solitude” as vital for the scientific worker. She divorced twice, later remarking that, when juggling marriage, science, and her children, “something has to go”. Despite her famed anti-establishment views, her awards and positions were legion, and included the coveted Darwin-Wallace Medal and America’s National Medal of Science.

Looking back, there was a certain pregnant poignancy about that little lecture room on that quiet summer afternoon. Margulis’s shameless enthusiasm, her insatiable curiosity – “I hear you have very good algae in Oxford; when can I go searching?” – as well as her passion for the smallest of animals, now strike a painful note. With her distinctive, faintly gravelled voice, she spoke earnestly and excitedly about her future projects, and, in the brief conversation we were lucky to have afterwards, she chatted with an affable, effervescent energy that inspired us all.

Charles Darwin once remarked that anyone “who dares to waste one hour of time has not discovered the value of life”. Lynn Margulis was an astonishing and visionary figure, with an insatiable appetite for knowledge. I believe – and I don’t think I’m alone – that Darwin and her would have got on like a house on fire.

She is survived by her four children.

Like naughty schoolchildren put on report, 15 of the 17 eurozone countries responded with tears and tantrums to Standard & Poor’s decision to place them on a negative “creditwatch” earlier this month. Threatened with the downgrade of their sovereign debt, some politicians resorted to denial – “a wild exaggeration and also unfair” inveighed Jean-Claude Junker, prime minister of Luxembourg. Others muttered accusations of Anglo-Saxon bias – “American rating agencies and fund managers are working against the eurozone” claimed Rainer Bruderle of Germany’s FDP. Christian Noyer, head of the Bank of France, argued last weekend that on the basis of economic fundamentals, “They should begin by downgrading the United Kingdom which has bigger deficits, more debt, higher inflation, less growth than us and where credit is shrinking”. If I go down, I’m taking you with me. And the furore looks set to continue, since Fitch announced last Friday that it too would be putting six European countries on the naughty step of negative watch.

However, the hullabaloo in Europe’s political playground has not been reflected in financial markets. In the wake of S&P’s news, eurozone government bond yields (the interest paid to creditors) hardly increased at all and actually fell in Italy and Spain. Commentators largely rushed to defend credit rating agencies from the protestations of European officials. S&P et al. didn’t reveal anything that investors didn’t already know, hence the markets’ limited reaction. Indeed, the sharp fall in value of many European bonds, such as those of Italy and France, is just one indication that the EU’s structural weaknesses have been evident for months. The role of credit rating agencies is merely to improve the flow of information about the creditworthiness of governments. What’s more, they’re actually good at this. Yes, their performance on US mortgages was spectacularly poor. But they have consistently downgraded sovereign debt a year before each government default since 1975. ‘Why shoot the messenger?’ therefore seems a legitimate retort to huffy politicians calling for the credit rating industry to be regulated and even silenced.

The trouble is, the ratings put forward by agencies do much more than merely state an opinion. If S&P followed through with its threat of downgrading eurozone debt, it would have a real impact on the region’s economy. First, it could spell doom for Europe’s €440bn bailout fund, the European Financial Stability Facility (EFSF). If any of the six triple A- rated eurozone countries that guarantee the rescue fund are downgraded, the EFSF will also lose its top credit rating, greatly reducing its ability to assist indebted countries. A French downgrade, for example, would drain the pot of €158bn of French guarantees. Taking into account the ongoing commitments to Greece, Ireland and Portugal, this would leave around €150bn, nowhere near enough cash to deal with the increasing strains on Italy and Spain.

Then there are the banks. Sovereign downgrades usually result in a subsequent downgrade of the banking system. This is because they compound economic strains, increase the cost of bank debts and, most importantly, reduce the value of sovereign bonds, which typically comprise 10% of a bank’s balance sheet. These additional problems are the last thing European banks need at a time when they are desperately trying to strengthen their capital bases and restore confidence among shareholders. The risk of default from the two largest eurozone banks is already the highest it has been since the 2008 financial crisis. A downgrade may tip the banking system over the edge.

But its not just Europe’s economy that is vulnerable to credit rating agencies’ decisions. Controversially, agencies seem to have power over politics as well. Despite the claim by S&P’s director of European ratings that the agency is “not in the business of policy making, that’s the business of elected officials”, S&P seems both conscious of its political influence and determined to maximize it. It can be no coincidence that its announcement that 15 eurozone countries could stand to lose their ratings came mere days before a European Union summit that intended to construct a solution to the eurozone crisis. This tactic was also seen in the summer when S&P threatened to downgrade US bonds in the middle of Congress’s negotiations over the debt ceiling. Moreover, the report that accompanied the agency’s warning was full of policy recommendations, including “a greater pooling of fiscal resources and obligations” and “mutual budgetary oversight”. The fact that the agency tied its ratings decision to the outcome of the summit lends credence to the view that it was trying to force politicians’ hands.

Yet, the answer is not to jump to over-regulation of agencies. The European Commission thankfully shelved its idea to ban changes to sovereign credit ratings of countries facing “exceptional circumstances”. Not only would this do little to reassure markets if a country were entering a crisis, it would impinge on agencies’ freedom of speech. Instead, credit ratings should be taken out of regulations, such as central bank collateral requirements and rules that limit which securities certain investors are allowed to hold. This would prevent the repercussions of a rating change being so widespread throughout the financial system. Steps have been taken in this direction. The Dodd-Frank reforms in the US require that regulators replace all references to credit ratings with “other standards of creditworthiness”. Yet much more needs to be done, particularly by policy-makers in Europe, if reliance on ratings is to be reduced.

Finally, the credit rating agencies also need to exercise the influence they yield more responsibly.   Announcing the potential of a downgrade to what were previously considered some of the safest assets around was one thing. Doing so at a time when investors were already nervously awaiting the outcome of the most important European summit this year was unnecessarily inflammatory. It is true that in the event the markets stayed calm. But S&P’s actions could well have sparked a panic. If this had led, for example, to the collapse of a European bank, politicians’ accusations that agencies were deliberately destabilizing the currency union would have rung true. The eurozone is in enough of a mess as it is, without S&P making it worse. Europe should treat the credit rating agencies with respect and vice versa.