How germs made history. Greenhouse gas emissions keep rising but USA and Europe are still the major causes of global warming.  

Measles and malaria banish Muhammad and Mao

Move over Alexander, Attila, Genghis Khan, Hannibal, George Washington, Napoleon and all your attention-grabbing mates. We’re rolling out the red carpet for Yersinia pestis, Variola major, Plasmodium falciparum, Vibrio cholerae and all their little friends. It hasn’t been Great Men (sorry, but it is pretty much only the males who have been remembered) that have determined the arc of human history; it has been microorganisms – bacteria, viruses and protozoa. Or at least that’s the hypothesis advanced by Jonathan Kennedy in ‘Pathogenesis. How Germs Made History’, part of my holiday season reading.

Kennedy’s story starts long before humans began to record their history in any systematic way, say 5,000 years ago, and long before Homo sapiens evolved, say 300,000 years ago.

Anaerobic bacteria emerged 3.6 billion years ago but life’s big breakthrough occurred with the appearance of cyanobacteria 2.5 billion years ago. Cyanobacteria (often referred to as ‘blue-green algae’ even though they aren’t algae) were the first organisms to photosynthesise. One of the outcomes of the new way of capturing, storing and releasing energy was a significant increase in the levels of oxygen in the oceans and atmosphere. Without cyanobacteria and The Great Oxidation event, it is highly unlikely that multicellular, let alone intelligent, life would have evolved. It was, arguably, the most important event in human history.

The main body of Pathogenesis consists of eight chapters where Kennedy describes the plagues that have taken dominant roles in determining the course of human affairs during various stages of recorded human history. Kennedy’s chapters move from palaeolithic and neolithic times, through the heydays of Greece and Rome and the Medieval period, to the plagues of the last 600 hundred years that have been associated with colonisation, revolutions, industrialisation and poverty. There is, not surprisingly, a strong emphasis on Europe, even when matters in the Americas and Africa are being discussed.

If one is looking for the second most important event in human history, the domestication of animals (‘the worst mistake in the history of the human race’, according to Jared Diamond) during the Neolithic Revolution, say 7-12,000 years ago, is a strong candidate. From this point on, plagues have beset humans as a result of microorganisms passing freely from animals to humans and then between humans living in large, mixed communities rather than small family groups. The new infectious diseases caused many deaths but the lucky individuals who survived went on over generations to establish populations with some level of immunity. Even if the immunity was only partial, it was enough, Kennedy frequently argues, to give that population a survival advantage over populations not previously exposed to the troublesome infectious agents.

So, for instance, the very small armies of Cortes and Pizarro were able to defeat, plunder and destroy far larger civilisations, that had their own well-trained forces, in Central and South America not because of their better military technologies, better organisation or better god, but because the respiratory and gastrointestinal diseases and smallpox that the Europeans brought with them killed up to 80% of the inhabitants, often racing ahead of, rather than simply accompanying, the European invaders.

In contrast, European colonisers didn’t do so well in West Africa (the ‘white man’s grave’) where the indigenous peoples had developed a degree of immunity to malaria and yellow fever to which the Europeans were highly vulnerable. Colonisation became feasible only when the Europeans started using quinine to treat malaria.

Unfortunately, the relative immunity of west Africans to malaria and yellow fever worked to their catastrophic disadvantage in the Americas where it made them attractive as workers and then slaves in the mosquito-infested sugar and cotton fields of the Caribbean and the southern states of the USA. Kennedy argues that plantation owners preferred relatively immune, African slaves over vulnerable, imported European workers not because they didn’t need paying but because they provided a more reliable source of labour.

Kennedy provides many more examples of microbes determining human history, not least the role played by the Black Death (‘the plague’) in shaping the transition from feudalism to capitalism across Europe. It would, however, be remiss to create any impression that Kennedy tries to suggest that microorganisms are all that matters in history. His examples repeatedly highlight the crucial importance of the interactions of infectious agents with geopolitics and religion (particularly the recurrent battles for supremacy between European nations), new technologies, climate, trade and trade routes, ignorance and prejudice, and even natural events such as earthquakes and volcanoes.

Kennedy doesn’t entirely dismiss the importance of great men but asserts that ‘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.’

As it says on the back cover of Pathogenesis, ‘Humans did not make history – we played host’.

USA and Europe still principally responsible for climate change

Three of the figures in the somewhat technical but important Hansen et al paper that I discussed three months ago are reasonably comprehensible to the general reader. The first two below show the annual and cumulative fossil fuel-related CO2 emissions by country or region as a percentage of the global CO2 emissions from 1800 to 2020. The UK may be industrially diminished these days but it’s clear where the industrial revolution started and that Europe and the USA are still responsible for over a quarter of current emissions and over half of all emissions to date.

The responsibility for the dire situation we are in is driven home by the third figure which shows cumulative fossil fuel emissions per person from 1751 to 2020. The USA, Canada, Europe, Russia, Australia and Japan should all hang their heads in shame at their continued merciless refusal to accept full financial or moral responsibility for their past emissions.

GHGs keep rising

I keep showing variations on the theme of the graph below so that I can keep making the same crucial point: the only thing that really matters in terms of controlling climate change is reducing the concentration of greenhouse gases (GHG) in the atmosphere. To do that, we  have to drastically and rapidly reduce all GHG emissions and increase the amount of CO2 that nature and technology remove from the air. It doesn’t matter how much renewable energy we install or how many EVs we have on the road while we keep pumping GHGs into the air. Simply peaking emissions isn’t enough, they must be reduced.

So, what does this particular graph demonstrate? That total GHG emissions continue to increase, as they have since 1990. Most notably, that emissions of methane and CO2 from fossil fuels are still increasing. That, with the possible exception of land use (LULUCF), no individual source of emissions has decreased during this period.

Draw your own conclusions about the likelihood of keeping warming under 1.5^oC.

Tallaganda Forest reprieve

Regular readers will recall that towards the end of last year citizen action pressured the NSW Environmental Protection Authority to put a series of temporary halts on logging in the Tallaganda State Forest, east of Canberra. The good news now is that the Forestry Corporation of NSW has quietly announced online that it has changed the status of its activities in Tallaganda from ‘active’ to ‘complete’. This doesn’t mean that the forest is saved for ever but it does appear to remove any immediate threats. If they knew, I’m sure the greater gliders in the forest would be performing exuberant aerobatics.

This 6-minute video displays very nicely what has been saved.

I was wrong: females have determined history

‘The mosquito has determined the fates of empires and nations, razed and crippled economies, and decided the outcome of pivotal wars, killing nearly half of humanity along the way. She (only females bite) has dispatched an estimated 52 billion people from a total of 108 billion throughout our relatively brief existence. As the greatest purveyor of extermination we have ever known, she has played a greater role in shaping our human story than any other living thing with which we share our global village.’  Timothy Winegard (2019). The Mosquito. A human history of our deadliest predator.

Although the plasmodium organism responsible for malaria was first described in 1880, it was not until 1897 that Ronald Ross discovered that malaria was transmitted to humans by mosquitoes.

There are currently about a quarter of a million cases of malaria each year worldwide and about 600,000 deaths (1% of all deaths), mostly in Sub-Saharan Africa and mostly in young children.

Number of deaths per 100,000 people, 2019.

Malaria deaths by age worldwide, 1990-2019

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