Tag Archives: philosophy of biology

A Hive Mind of One

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My friend Mick alerted me that Carl Zimmer was featured in a recent episode of RadioLab dedicated to the subject of parasites (Abumrad, Jad and Robert Krulwich, “Parasites,” 7 September 2009). Despite being somewhat annoying in format and low-density in it’s information presentation, the show contains a number of points interesting to my project.

Hookworms

In the second part of the second segment (starting at 31:25), they deal with the symbiosis between hookworms and the human immune system. The segment consists of a profile of Jasper Lawrence, a man who had severe allergies and — having chased down a certain direction of research — decided to travel to Cameroon to infect himself with hookworms. The research in question is that of the hygiene hypothesis: the notion that many developed world afflictions, including allergies, result in part from the excessively sterile human environment. Asthma is 50 percent less likely in a person who has had a hookworm and in Africa allergies are almost entirely unknown. It is theorized that similar to the dependence of digestion upon a symbiotic relationship with non-human microflora of the digestive tract, the immune system is dependent on certain microorganisms for regulation and calibration of the immunoresponse. The complex chain of events that is the immunoresponse evolved in the constant presence of parasites, evolved around parasites; they have co-evolved to the point where their presence became necessary. “We function like rainforests; we’re ecosystems,” Mr. Lawrence says. This is the hypersea washing through humanity.

Toxoplasma Gondii

The final segment is on Toxoplasma Gondii (starting at 47:55), a parasite that lives in cats and makes their feces dangerous to pregnant women. Like many parasites, it has a multi-phase lifecycle that takes place in a multiple hosts. It only reproduces in members of the Felidae family (cats), but can live the remainder of its life in any warm-blooded creature. T. gondii is expelled by cats when they shit and the cat shit is ingested by other creatures (consumption of unwashed vegetables, inhaled while digging close to the ground — which is why pregnant women are advised against gardening). T. gondii needs to get back into the digestive tract of a cat to reproduce, so it wriggles its way to the amygdale, the part of the brain responsible for emotional reaction, and causes the host to become attracted to cats, thus, in the case of small mammals or birds, becoming easy prey for cats (it is Carl Zimmer’s argument in his book, Parasite Rex that in this way parasites are like ecological catalysts, spinning food webs ever more tightly together).

But then there is the question of humans. It is one thing to say that T. gondii might make a bird or a rat suicidal. But T. gondii infects humans too. What then?

The scientific interviewee for the segment is Robert Sapolsky, a professor of neurology at Stanford University. On the question of T. gondii altering human behavior, he declares it highly plausible:

Sapolsky: Pure speculation, but people who think about this stuff view it as not purely speculative. The notion that toxo can produce some sort of attraction to cats in humans: they don’t think it’s all that crazy.

That’s right: crazy cat lady is that way because she’s been body-snatched by toxoplasma gondii.

Less controversial than the idea that T. gondii might be making crazy cat people out of us is the idea that it can make people more prone to engage in risky behavior. Dr. Sapolsky mentions two independent studies that show that people infected with T. gondii are two to six times more likely to get in a car crash than those not infected. With this information in hand, host and guest make the larger point:

Ellen Horne: It might be possible — might be possible — that toxo is guiding our emotions, changing who we are in some basic way. And if you consider that toxo might just be one of thousands of tiny little parasites inside us, pulling our strings from the inside, well that thought is pretty creepy.

Sapolsky: Even if the entire lesson with toxo is that a small subset of infected people now have one half of one percent more likelihood of wanting to drive really recklessly, even lurking in that one half of one percent are some serious implications for thinking about free will. We haven’t a clue the biology lurking in the background that makes free will seem a little bit suspect.

I’m less concerned with that old philosophical saw of free will versus determinism, than with extending an idea from segment on the hookworms. Mr. Lawrence says, “We function like rainforests; we’re ecosystems.” Presumably he is referring to our bodies. But the implication of toxoplasma gondii is that we are ecosystems in out minds as well. To the naïve sort of homunculus, Herman’s Head notion of consciousness, we must now add a few animal spirits.

Update, 23 October 2009: For instance this woman must have a pretty severe infection of T. gondii.

Update no. 2, 5 June 2010: Parasitogenic felinophilia (Toxoplasma gondii) may be treatable with haloperidol, an antipsychotic (“A Game of Cat and Mouse,” The Economist, 3 June 2010). Repost from my twitter feed.

Sociobiology as the Transcendence of Biological Ecology

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The central idea of sociobiology is that the emergence of social creatures (herd animals) coincided with the creation of what might be termed a socio-cultural environment. The socio-cultural environment is as much an environment that social creatures inhabited as the material environment. As social creatures evolve, two things happen to the socio-cultural environment:

  1. As with evolution of species morphology, the maximum complexity of socio-cultural environments increases (there is selection pressure on the entire socio-cultural environment as, say, predators develop way of thwarting or exploiting the social aspect of their prey and the social species evolve to countervail this development, e.g. parasitic cordyceps and ants; that is, there is species-level selection, since a social characteristic unrecognized by a counterpart comes to nothing; consider this as an analogy for fourth generation warfare).

  2. Subsequent generations of herd animals come to rely ever more heavily upon social cohesion — as opposed to horns, honed perceptive apparatus, efficient digestion, et cetera — as their primary means of survival.

As this socio-cultural environment becomes more sophisticated and intricate and increasingly important as a means of survival, the socio-cultural environment grows in importance as the universe of factors shaping the evolution of social animals, while the objective, geological, hydrological and biological environment recedes in its evolutionary force.

Sexual selection (a type of sociobiological selection, as opposed to natural or Malthusian selection) is the sort of selection pressure that a species faces when its fellows, rather than the environment becomes the main challenge to getting its genes into the future. The shifting balance of natural selection and sexual selection in the play of evolutionary forces is meta-evolutionary. Evolution is recursive, with developments in the subjects of evolution backpropigating into the mechanism itself. In this respect every new thing in the universe (or at least in the effective realm) can potentially alter the functioning of the evolutionary dynamic. In this broadened perspective, the idea of machine or meme evolution supplanting biological evolution should not be so surprising.

Among a certain sector of the wildly technologically enthusiastic (among whom I count myself, though Matthew Crawford’s Shop Class as Soulcraft: An Inquiry Into the Value of Work is presently doing a lot to kick the piss out of this pretention), there is a notion that humans are rapidly disencumbering themselves of the material world and constructing for ourselves a world of pure ideas, information, mind-stuff. At some point in human history saber-toothed tigers, virulent microbes, droughts and tar pits ceased to be the primary challenge to humans seeking to survive and reproduce. Such extra-human threats were replaced as the primary danger by human-originating threats such as careening contraptions, shoddy construction techniques, insufficient precaution with the kitchen fire, marauding hoplites, jilted dagger-wielding lovers, corrupt institutions and flawed regimes of succession in governance. It is at the point where today it is plausible that the human socio-cultural environment has attained a level of preponderance where even the level of environmental catastrophe such as an asteroid strike that caused the mass extinctions of the past might be thwarted by the constituents of the human socio-cultural environment (on the other hand, the complexity of our socio-cultural environment might be just the sort of run-away biological factor that caused past mass extinction such as the oxygen catastrophe or the Canfield ocean thesis of the Permian–Triassic extinction event). In this conception, it is usually the the information revolution, the invention of the computer — a brain-like device — that is the cause of this transcending of matter. The advent of technology was not the key turning point. The recognition of sociobiology is that this trend is an aspect of evolution; that it long predates not only technology, but also even predates humans. In this way, we are not unique, not the penultimate branch of the tree of life, but only the latest in a succession of forms.

Update, 15 September 2009: It’s worth noting that while computers are not the revolution, nor the source of the revolution, they do form a paradigm, shaping our conceptualizations in ways that allow us to perceive the revolution.

Information Phenotype

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The fractal tree at the corner of 18th and Lamont, Washington, D.C., 29 April 2009

I have previously commented on my love of the movie π (“The Supernovae in Your Coffee Cup,” 2 November 2008). It left me with two enduring images: mixing coffee and cream as an example of turbulence, previously discussed; and the branching of tree limbs as an example of fractal symmetry. I love winter for its exposure of this fabulous phenomena, innocuously right over our heads. I am always a little sad for the arrival of spring and the enshrouding of all these thought-provoking fractals in greenery.

The picture above is of my favorite tree in the neighborhood where I live. The degree to which the pattern of major arc over two-thirds of growth length followed by sharp break and lesser arc over remainder of growth length is repeated trunk to twig is amazing. Notice the arc of the trunk: unlike many trees which follow one rule for trunk and a separate rule for the branches, this tree follows a single rule throughout.

We think of a fractal as a recursive algorithm, a mathematical formula. But there’s no math in that tree. The recipe for that fractal is coded somewhere in the tree’s DNA. But the DNA contains no fractal. The DNA is a bunch of nucleotides that are transcribed by messenger RNA that code amino acids that assemble into proteins that form the structures of cells. The cells then split and differentiate in response to a complex of internal chemical signals and environmental stimuli to grow in a pattern that is the fractal.

One might say that there is a fractal somewhere in that tree, but there are so many transformation rules between nucleotide sequence and fractal growth pattern, that it is only in a manner of speaking. I am reminded of Wittgenstein’s discussion of what constitutes following a rule and going against it (Philosophical Investigations, trans. G. E. M. Anscombe [Malden, Mass.: Blackwell, 1953]):

198. “But how can a rule shew me what I have to do at this point? Whatever I do is, on some interpretation, in accord with the rule.” — That is not what we ought to say, but rather: any interpretation still hangs in the air along with what it interprets, and cannot give it any support. Interpretations by themselves do not determine meaning.

“Then can whatever I do be brought into accord with the rule?” — Let me ask this: what has the expression of a rule — say a sign-post — got to do with my actions? What sort of connection is there here? — Well perhaps this one: I have been trained to react to this sign in a particular way, and now I so react to it.

But that is only to give the causal connection; to tell how it has come about that we now go by the sign-post; not what this going-by-the-sign really consists in. On the contrary; I have further indicated that a person goes by a sign-post only in so far as there exists a regular use of sign posts, a custom.

199. Is what we call “obeying a rule” something that it would be possible for only one man to do, and to do only once in his life? — This is of course a note on the grammar of the expression “to obey a rule.”

It is not possible that there should have been only one occasion on which someone obeyed a rule. It is not possible that there should have been only one occasion on which a report was made, an order given or understood; and so on. — To obey a rule, to make a report, to give an order, to play a game of chess, are customs (uses, institutions).

To understand a sentence means to understand a language. To understand a language means to be master of a technique.

200. It is, of course, imaginable that two people belonging to a tribe unacquainted with games should sit at a chess-board and go through the moves of a game of chess; and even with all the appropriate mental accompaniments. And if we were to see it we should say they were playing chess. But now imagine a game of chess translated according to certain rules into a series of actions which we do not ordinarily associate with a game — say into yells and stamping of feet. And now suppose those two people to yell and stamp instead of playing the form of chess that we are used to; and this in such a way that their procedure is translatable by suitable rules into a game of chess. Should we still be inclined to say that they were playing a game? What right would one have to say so?

201. This is our paradox: no course of action could be determined by a rule, because every course of action can be made out to accord with the rule. The answer was: if everything can be made out to accord with the rule, then it can also be made out to conflict with it. And so there would be neither accord nor conflict here.

It can be seen that there is a misunderstanding here from the mere fact that in the course of our argument we gave one interpretation after another; as if each one contented us at least for a moment, until we thought of yet another standing behind it. What this shews is that there is a way of grasping a rule which is not an interpretation, but which is exhibited in what we call “obeying the rule” and “going against it” in actual cases.

Of course Wittgenstein is writing about social phenomena where custom and training are factors, but the undecidability of rules is the point here. Socially dogmatic, we are dismissive of blatant divergence from consensus. Less dogmatic — but not free of dogma — science resorts to the metaphysical-aesthetic notion of Ockham’s razor with which to cut through the myriad of rules that might potentially be made to accord with observed behavior. Is there really a fractal in the tree’s DNA? The fractal pattern of tree growth is but an interpretation of the tree’s DNA — an interpretation that would be different given a differing machinery of RNA transcription, amino acid assembly, protein expression, etc.