On violence and gratitude.

On violence and gratitude.

Although I consider myself a benevolent tyrant, some of my cells have turned against me.  Mutinous, they were swayed by the propaganda of a virus and started churning out capsids rather than helping me type this essay.  Which leaves me sitting at a YMCA snack room table snerking, goo leaking down my throat and out my nose.

Unconsciously, I take violent reprisal against the traitors.  I send my enforcers to put down the revolt – they cannibalize the still-living rebels, first gnawing the skin, then devouring the organs that come spilling out.  Then the defector dies.

CD8+ T cell destruction of infected cells by Dananguyen on Wikimedia.

My cells are also expected to commit suicide whenever they cease to be useful for my grand designs.  Any time a revolutionary loses the resolve to commit suicide, my enforcers put it down.  Unless my internal surveillance state fails to notice in time – the other name for a cell that doesn’t want to commit suicide is “cancer,” and even the most robust immune system might be stymied by cancer when the traitor’s family grows too large.

Worse is when the rebels “metastasize,” like contemporary terrorists.  This word signifies that the family has sent sleeper agents to infiltrate the world at large, attempting to develop new pockets of resistance in other areas.  Even if my enforcers crush one cluster of rebellion, others could flourish unchecked.

How metastasis occurs. Image by the National Cancer Institute on Wikimedia.

I know something that perhaps they don’t – if their rebellion succeeds, they will die.  A flourishing cancer sequesters so many resources that the rest of my body would soon prove too weak to seek food and water, causing every cell inside of me to die.

But perhaps they’ve learned my kingdom’s vile secret – rebel or not, they will die.  As with any hereditary monarchy, a select few of my cells are privileged above all others.  And it’s not the cells in my brain that rule.

Every “somatic cell” is doomed.  These cells compose my brain and body.  Each has slight variations from “my” genome – every round of cell division introduces random mutations, making every cell’s DNA slightly different from its neighbors’.

The basic idea behind Richard Dawkins’s The Selfish Gene is that each of these cells “wants” for its genome to pass down through the ages.  Dawkins argued that familial altruism is rational because any sacrifice bolsters the chances for a very similar genome to propagate.  Similarly, each somatic cell is expected to sacrifice itself to boost the odds for a very similar genome carried by the gametes.

Only gametes – the heralded population of germ cells in our genitalia – can possibly see their lineage continue.  All others are like the commoners who (perhaps foolishly) chant their king or kingdom’s name as they rush into battle to die.  I expect them to show absolute fealty to me, their tyrant.  Apoptosis – uncomplaining suicide – was required of many before I was even born, like when cells forming the webbing between my fingers slit their own bellies in dramatic synchronized hara-kiri.

Human gametes by Karl-Ludwig Poggemann on Flickr.

Any evolutionary biologist could explain that each such act of sacrifice was in a cell’s mathematical best interest.  But if I were a conscious somatic cell, would I submit so easily?  Or do I owe some sliver of respect to the traitors inside me?

The world is a violent place.  I’m an extremely liberal vegan environmentalist – yet it takes a lot of violence to keep me going.

From Suzana Herculano-Houzel’s The Human Advantage:

image (1)Animals that we are, we must face, every single day of our lives, the consequences of our most basic predicament: we don’t do photosynthesis.  For lack of the necessary genes, we don’t just absorb carbon from the air around us and fix it as new bodily matter with a little help from sunlight.  To survive, we animals have to eat other living organisms, whether animal, vegetable, or fungus, and transform their matter into ours.

And yet the violence doesn’t begin with animals.  Photosynthesis seems benign by comparison – all you’d need is light from the sun! – unless you watch a time-lapsed video of plant growth in any forest or jungle.

The sun casts off electromagnetic radiation without a care in the world, but the amount of useful light reaching any particular spot on earth is limited.  And plants will fight for it.  They race upwards, a sprint that we sometimes fail to notice only because they’ve adapted a timescale of days, years, and centuries rather than our seconds, hours, and years.  They reach over competitors’ heads, attempting to grab any extra smidgen of light … and starving those below.  Many vines physically strangle their foes.  Several trees excrete poison from their roots.  Why win fair if you don’t have to?  A banquet of warm sunlight awaits the tallest plant left standing.

And so why, in such a violent world, would it be worthwhile to be vegan?  After all, nothing wants to be eaten.  Sure, a plant wants for animals to eat its fruit – fruits and animals co-evolved in a system of gift exchange.  The plant freely offers fruit, with no way of guaranteeing recompense, in hope that the animal might plant its seeds in a useful location.

But actual pieces of fruit – the individual cells composing an apple – probably don’t want to be eaten, no more than cancers or my own virus-infected cells want to be put down for the greater good.

A kale plant doesn’t want for me to tear off its leaves and dice them for my morning ramen.

But by acknowledging how much sacrifice it takes to allow for us to be typing or reading or otherwise reaping the pleasures of existence, I think it’s easier to maintain awe.  A sense of gratitude toward all that we’ve been given.  Most humans appreciate things more when we think they cost more.

We should appreciate the chance to be alive.  It costs an absurd amount for us to be here.

But, in the modern world, it’s possible to have a wonderful, rampantly hedonistic life as a vegan.  Why make our existence cost more when we don’t have to?  A bottle of wine tastes better when we’re told that it’s $45-dollar and not $5-dollar wine, but it won’t taste any better if you tell somebody “It’s $45-dollar wine, but you’ll have to pay $90 for it.”

Personally, I’d think it tasted worse, each sip with the savor of squander.

On evolution (and why there aren’t more black plants).

CaptureAs I was reading Freeman Dyson‘s recent collection Dreams of Earth and Sky, specifically his essay on democratizing genetic manipulation, I came across the following passage:

“For a plant growing in a hot climate, it is advantageous to reflect as much as possible of the sunlight that is not used for growth.  There is plenty of sunlight, and it is not important to use it with maximum efficiency.  The plants have evolved with chlorophyll in their leaves to absorb the useful red and blue components of sunlight and to reflect the green.  That is why it is reasonable for plants in tropical climates to be green.  But this logic does not explain why plants in cold climates where sunlight is scarce are also green.  We could imagine that in a place like Iceland, overheating would not be a problem, and plants with black leaves using sunlight more efficiently would have an evolutionary advantage.  For some reason that we do not understand, natural plants with black leaves never appeared.  Why not?  Perhaps we shall not understand why nature did not travel this route until we have traveled it ourselves.”

I was puzzled why he posed this question.  Dyson has previously addressed theories as to the origin of life (in fairness, perhaps I should quote a sentence from the beginning of that work: “This apology for a physicist venturing into biology will serve for me as well as for Schrodinger, although in my case the risk of the physicist making a fool of himself may be somewhat greater.”  Dyson makes very clear that he’s addressing these topics speculatively), so I would’ve expected a more nuanced treatment of evolution.

Evolution is not an engineer.  Evolution is a tinkerer.  If something is broken, or misfit, or maladjusted, it won’t be scrapped.  The energetic barrier is too high to expect nature to routinely start again from nothing and construct a suitable replacement.  If evolution stumbles across something that seems broken, it will be fixed, fixed poorly, fixed with duct tape and twine until it’s just barely adequate for its intended function.

Leaf_1_webFor natural selection to give rise to a plant that uses silicon to harvest sunlight (which is why Dyson was discussing plants with black leaves above.  He was speculating upon the possibility that genetic manipulation could yield plants with silicon-based rather than chlorophyll-based sunlight collection, potentially resulting in a higher energetic yield), numerous processes must be optimized.  Extraction of silicon from the earth.  Incorporating it into an electron transport chain.  Etc.  But until all of that is somewhat functional, there won’t be any selective pressure.  Why would generation after generation of offspring be enriched for improved silicon uptake if there is no beneficial use for silicon?  Why would genetic sequences coding for protein folds able to cradle a silicon cofactor be enriched in the absence of silicon, or any way to use the energy thus captured?

(Hint: they won’t be.)

It’s possible that this sounds vaguely reminiscent of the claims made by creationists.  That evolutionary processes cannot enact macroscale changes because too much needs to go right all at once.  But there’s a difference.  In the absence of chlorophyll-producing plants, given sufficient time, a species might evolve a means to use silicon to capture light from the sun.  But, for a plant to do it?  This is dramatically more difficult than for an organism to start from scratch.  Plants already have a system that works well enough. That pre-existing system suppresses innovation.

For instance, I’m typing this essay on a QWERTY keyboard.  The layout was designed to slow my fingers down, ensure that the spindly arms of my typewriter wouldn’t collide with one another.  The arms are long gone by now.  And, sure, northern plants are free of heat constraints.  But with a good-enough system in place, evolution will not bother breaking out the twine to jury-rig a better one.  Actually, “good enough” isn’t even necessary; “barely adequate” is often sufficient to stifle innovation.  Probably the lowest-hanging analogy for that is the recent attempt to “revamp” the way healthcare is delivered in this country while still preserving the role of all our existing insurance providers.

The other thing Dyson’s passage made me curious about is, why would he expect a better sunlight harvester to arise only at high latitudes?  Yes, temperatures are cooler there, but overheating due to efficient sunlight capture is only a problem when exposed to high loads of radiation.  But I was under the impression that plants in the lower stories of rainforests, for instance, were exposed to very low amounts of sunlight — personally, if I thought a silicon-based sunlight capture system was going to evolve anywhere, I’d put my money on the rainforest.

CaptureThis graph is from Campbell and Aarup’s study, “Photosynthetically available radiation at high latitudes.”  And, sure, over the course of a year the light levels at high latitude are lower than near the equator.  Not something you needed to scope a fancy graph to realize: it’s sunnier in Texas than in Alaska??  But I thought it might be worth seeing to get a sense of the numbers.  The axis gives values for number of photons per area per day, and if we’re interested in Dyson’s reasoning, it’s worth looking up some numbers for light levels in tropical rainforests.

Rainforest numbers shouldn’t match the equatorial line shown in the graph above.  Or, well, they should, but only for the tallest plants in any forest.  The majority of plants in tropical forests are exposed to very low levels of light in the underbrush.  As opposed to short scruffy plants in the glacially-flattened upper latitudes, which can expect to soak up the full quantity of incipient solar radiation, tropical plants often grow in shade.

Some numbers are tucked away in the methods section of Coste et al.’s “A cost-benefit analysis of acclimation to low irradiance in tropical rainforest tree seedlings: leaf life span and payback time for leaf deployment”  (unfortunately, they’re using the phrase “payback time” in its economics / game theory sense, not the action movie sense.  Their article features zero leaves embarking on a vengeful rampage): seems a plant striving through the undergrowth might receive on the order of 2 moles of photons per meter squared per day — well below the light levels at high latitude through almost the entire year.

All of which is to say that, well, I was a little surprised by Dyson’s evolutionary argument.  Because he’s clearly quite intelligent.  But evolution is a tricky topic, and there are a lot of subtle misconceptions out there.