Later On

A blog written for those whose interests more or less match mine.

An evolutionary account of humans as cells in the body politic

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I don’t recall Hobbes as being a bottom-up thinker. His Leviathan, pictured above, is a great composite creature consisting of a state and its inhabitants, with the monarch as its head, directing the enterprise. Still, the idea of the people as cells, industriously working separately and as an unintended and unforeseen outcome creating cumulatively a human culture, came to me as I read this passage in The Evolution of Everything, by Matt Ridley:

[T]he diagnostic feature of life is that it captures energy to create order. This is also a hallmark of civilisation. Just as each person uses energy to make buildings and devices and ideas, so each gene uses energy to make a structure of protein. A bacterium is limited in how large it can grow by the quantity of energy available to each gene. That’s because the energy is captured at the cell membrane by pumping protons across the membrane, and the bigger the cell, the smaller its surface area relative to its volume. The only bacteria that grow big enough to be seen by the naked eye are ones that have huge empty vacuoles inside them.

However, at some point around two billion years after life started, huge cells began to appear with complicated internal structures; we call them eukaryotes, and we (animals as well as plants, fungi and protozoa) are them.

Nick Lane argues that the eukaryotic (r)evolution was made possible by a merger: a bunch of bacteria began to live inside an archeal cell (a different kind of microbe). Today the descendants of these bacteria are known as mitochondria, and they generate the energy we need to live. During every second of your life your thousand trillion mitochondria pump a billion trillion protons across their membranes, capturing the electrical energy needed to forge your proteins, DNA and other macromolecules.

Mitochondria still have their own genes, but only a small number – thirteen in us. This simplification of their genome was vital. It enabled them to generate far more surplus energy to support the work of ‘our genome’, which is what enables us to have complex cells, complex tissues and complex bodies. As a result we eukaryotes have tens of thousands of times more energy available per gene, making each of our genes capable of far greater productivity. That allows us to have larger cells as well as more complex structures. In effect, we overcame the size limit of the bacterial cell by hosting multiple internal membranes in mitochondria, and then simplifying the genomes needed to support those membranes.

There is an uncanny echo of this in the Industrial (R)evolution. In agrarian societies, a family could grow just enough food to feed itself, but there was little left over to support anybody else. So only very few people could have castles, or velvet coats, or suits of armour, or whatever else needed making with surplus energy. The harnessing of oxen, horses, wind and water helped generate a bit more surplus energy, but not much. Wood was no use – it provided heat, not work. So there was a permanent limit on how much a society could make in the way of capital – structures and things.

Then in the Industrial (R)evolution an almost inexhaustible supply of energy was harnessed in the form of coal. Coal miners, unlike peasant farmers, produced vastly more energy than they consumed. And the more they dug out, the better they got at it. With the first steam engines, the barrier between heat and work was breached, so that coal’s energy could now amplify the work of people. Suddenly, just as the eukaryotic (r)evolution vastly increased the amount of energy per gene, so the Industrial (R)evolution vastly increased the amount of energy per worker. And that surplus energy, so the energy economist John Constable argues, is what built (and still builds) the houses, machines, software and gadgets – the capital – with which we enrich our lives. Surplus energy is indispensable to modern society, and is the symptom of wealth. An American consumes about ten times as much energy as a Nigerian, which is the same as saying he is ten times richer. ‘With coal almost any feat is possible or easy,’ wrote William Stanley Jevons; ‘without it we are thrown back into the laborious poverty of early times.’ Both the evolution of surplus energy generation by eukaryotes, and the evolution of surplus energy by industrialisation, were emergent, unplanned phenomena.

But I digress. Back to genomes. A genome is a digital computer program of immense complexity. The slightest mistake would alter the pattern, dose or sequence of expression of its 20,000 genes (in human beings), or affect the interaction of its hundreds of thousands of control sequences that switch genes on and off, and result in disastrous deformity or a collapse into illness. In most of us, for an incredible eight or nine decades, the computer program runs smoothly with barely a glitch.

Consider what must happen every second in your body to keep the show on the road. You have maybe ten trillion cells, not counting the bacteria that make up a large part of your body. Each of those cells is at any one time transcribing several thousand genes, a procedure that involves several hundred proteins coming together in a specific way and catalysing tens of chemical reactions for each of millions of base pairs. Each of those transcripts generates a protein molecule, thousands of amino acids long, which it does by entering a ribosome, a machine with tens of moving parts, capable of catalysing a flurry of chemical reactions. The proteins themselves then fan out within and without cells to speed reactions, transport goods, transmit signals and prop up structures. Millions of trillions of these immensely complicated events are occurring every second in your body to keep you alive, very few of which go wrong. It’s like the world economy in miniature, only even more complex.

It is hard to shake the illusion that for such a computer to run such a program, there must be a programmer. Geneticists in the early days of the Human Genome Project would talk of ‘master genes’ that commanded subordinate sequences. Yet no such master gene exists, let alone an intelligent programmer. The entire thing not only emerged piece by piece through evolution, but runs in a democratic fashion too. Each gene plays its little role; no gene comprehends the whole plan. Yet from this multitude of precise interactions results a spontaneous design of unmatched complexity and order. There was never a better illustration of the validity of the Enlightenment dream – that order can emerge where nobody is in charge. The genome, now sequenced, stands as emphatic evidence that there can be order and complexity without any management.

I’m reminded of something I blogged earlier from a paper by Olivia Judson in Nature:

The history of the life–Earth system can be divided into five ‘energetic’ epochs, each featuring the evolution of life forms that can exploit a new source of energy. These sources are: geochemical energy, sunlight, oxygen, flesh and fire. The first two were present at the start, but oxygen, flesh and fire are all consequences of evolutionary events. Since no category of energy source has disappeared, this has, over time, resulted in an expanding realm of the sources of energy available to living organisms and a concomitant increase in the diversity and complexity of ecosystems. These energy expansions have also mediated the transformation of key aspects of the planetary environment, which have in turn mediated the future course of evolutionary change. Using energy as a lens thus illuminates patterns in the entwined histories of life and Earth, and may also provide a framework for considering the potential trajectories of life–planet systems elsewhere.

Free energy is a universal requirement for life. It drives mechanical motion and chemical reactions—which in biology can change a cell or an organism1,2. Over the course of Earth history, the harnessing of free energy by organisms has had a dramatic impact on the planetary environment3,​4,​5,​6,​7. Yet the variety of free-energy sources available to living organisms has expanded over time. These expansions are consequences of events in the evolution of life, and they have mediated the transformation of the planet from an anoxic world that could support only microbial life, to one that boasts the rich geology and diversity of life present today. Here, I review these energy expansions, discuss how they map onto the biological and geological development of Earth, and consider what this could mean for the trajectories of life–planet systems elsewhere. . .

The evolution of human culture (as I repeatedly mention, and as described by Susan Blackmore in The Meme Machine—and indeed in Ridley’s book quoted above) follows the same undirected, bottom-up process as evolution of lifeforms. No great leader says, “Now let’s find a better source of energy—coals would work. Go development machines and processes to use coal” just as no leader says, “We need new musical instruments and styles: invent the pianoforte and write sonatas for it” (nor do some animals think, “We should now become able to fly”). Individual cells do things on their own, and natural selection harmonizes the efforts over time.

And I sort of like the idea that all us humans are in effect cells working hard to generate little bits of human culture. I do it by blogging (and by writing a book on shaving). We don’t really know quite how it will all fit together, but that’s what natural selection takes care of.

Update: Just as the cell makes proteins of various kinds, following the templates provided by DNA and RNA, so too do individual humans produce memes of various kinds, guided by the template of one’s culture. In this case, though, the creation from the culture will also change the culture (cultural evolution). Thus the template is always changing, unlike DNA and RNA which change only occasionally—i.e., mutations. And mutations generally don’t help; it’s the rare mutation that makes a significant positive difference, like the mutation that led to lactose-tolerance.

But the same is true of cultural creations: many of those go nowhere and never really serve as a template. They have a brief heyday and wither away. No Pet Rocks today. Hula hoops survive, barely. The Frisbee seems well-established in its cultural niche.

Another example of a meme almost extinguished: the two-spirit idea of the Native Americans, about which I blogged today. That seems a very valuable meme (in terms of memes matching reality), and I hope it returns.

Written by LeisureGuy

30 May 2017 at 3:58 pm

Posted in Books, Evolution, Memes, Science

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