Category Archives: biology

Small animals have enormous brains for their size

One thing that surprised me when working on How Many Neurons Are There was the number of neurons in the brains of very small animals.

Let’s look a classic measurement, the brain-mass:body-mass ratio.* Smarter animals generally have larger brain sizes for their body mass, compared to animals of similar size. Among large animals, humans have famously enormous brains for our size – the highest of any large animal, it seems. But as we look at smaller animals, that ratio goes up again. A mouse has a comparable brain:body-mass ratio to a human. Getting even smaller, insects have higher brain:body-mass ratios than any vertebrate we know of: more like 1 in 6.

But brain mass isn’t quite what we want – brains are mostly water, and there are a lot of non-neuron cells in brains. Conveniently, I also have a ton of numbers put together on number of neurons. (Synapse counts might be better, but those are hard to come by for different species. Ethology would also be interesting.)

And the trend is also roughly true for neuron-count:body-mass. Humans do have unusually high numbers of neurons per kilogram than other animals, but far, far fewer than, for instance, a small fish or an ant.

neuron-body-count-ratio-and-mass

If you believe some variation on one of the following:

  • Different species have moral worth in proportion to how many neurons they have
  • Different animal species have moral worth in proportion to how smart they are
  • Different species have moral worth in proportion to the amount of complex thought they can do
  • Different species have moral worth in proportion to how much they can learn**

…then this explanation is an indication that insects and other small animals have much more moral worth than their small size suggests.

How much more?

Imagine, if you will, a standard 5-gallon plastic bucket.

emptybucket

Now imagine that bucket contains 300,000 ants – about two pounds.*** Or a kilogram, if you prefer.

Imagine the bucket. Imagine the equivalent of a couple large apples inside it.

bucketwithants

A bucket. Two pounds of ants.

Those ants, collectively, have as many neurons as you do.

bucketandhuman

(Graphic design is my passion.)

You may notice that an adult human brain actually weighs more than two pounds. What’s going on? Simply, insect brains are marvels of miniaturization. Their brains have a panoply of space-saving tricks, and the physical cells are much smaller.

🐜🐜🐜

*Aren’t the cool kids using cephalization quotients rather than brain-mass:body-mass ratios? Yes, when it comes to measurements of higher cognition in vertebrates, cephalization is (as far as I’m aware) thought of as better. But there’s debate about that too. Referring to abilities directly probably makes sense for assessing abilities. I don’t know much about this and it’s not the focus of this piece, anyway.

**Yes, I know that only the first question is directly relevant to this piece, and that all of the others are different. I’m just saying it’s evidence. We don’t have a lot of behavioral data on small animals anyways, but I think we can agree there’s probably a correlation between brain size and cognitive capacity.

***Do two pounds of “normal-sized” ants actually fit in a five-gallon bucket? Yes. I couldn’t find a number for “ant-packing density” in the literature, but thanks to the valiant efforts of David Manheim and Rio Lumapas, it seems to be between 0.3 gallons (5 cups) and 5.5 gallons. It depends on size and whether ants pack more like spheres or more like blocks.

🐜🐜🐜

Suggested readings: Brian Tomasik on judging the moral importance of small minds (link is to the most relevant part but the whole essay is good) and on “clock speeds” in smaller animal brains, Suzana Herculano-Houzel on neuron count and intelligence in elephants versus humansHow many neurons are there. (The last piece also contains most of the citations for this week. Ask if you want specific ones.)

This piece is crossposted to the Effective Altruism Forum.

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Spaghetti Towers

Here’s a pattern I’d like to be able to talk about. It might be known under a certain name somewhere, but if it is, I don’t know it. I call it a Spaghetti Tower. It shows up in large complex systems that are built haphazardly.

Someone or somethdesidesigning builds the first Part A.

20181220_204411.jpg

Later, someone wants to put a second Part B on top of Part A, either out of convenience (a common function, just somewhere to put it) or as a refinement to Part A.

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Now, suppose you want to tweak Part A. If you do that, you might break Part B, since it interacts with bits of Part A. So you might instead build Part C on top of the previous ones.

20181220_204759

And by the time your system looks like this, it’s much harder to tell what changes you can make to an earlier part without crashing some component, so you’re basically relegated to throwing another part on top of the pile.

bkajfeakfje

I call these spaghetti towers for two reasons: One, because they tend to quickly take on circuitous knotty tangled structures, like what programmers call “spaghetti code”. (Part of the problem with spaghetti code is that it can lead to spaghetti towers.)

Especially since they’re usually interwoven in multiple dimensions, and thus look more like this:

20181220_205553

“Can you just straighten out the yellow one without touching any of the others? Thanks.”

Second, because shortsightedness in the design process is a crucial part of spaghetti machines. In order to design a spaghetti system, you throw spaghetti against a wall and see if it sticks. Then, when you want to add another part, you throw more spaghetti until it sticks to that spaghetti. And later, you throw more spaghetti. So it goes. And if you decide that you want to tweak the bottom layer to make it a little more useful – which you might want to do because, say, it was built out of spaghetti – without damaging the next layers of gummy partially-dried spaghetti, well then, good luck.

Note that all systems have load-bearing, structural pieces. This does not make them spaghetti towers. The distinction about spaghetti towers is that they have a lot of shoddily-built structural components that are completely unintentional. A bridge has major load-bearing components – they’re pretty obvious, strong, elegant, and efficiently support the rest of the structure. A spaghetti tower is more like this.

SpaghettiFix

The motto of the spaghetti tower is “Sure, it works fine, as long as you never run lukewarm water through it and turn off the washing machine during thunderstorms.” || Image from the always-delightful r/DiWHY.

Where do spaghetti towers appear?

  • Basically all of biology works like this. Absolutely all of evolution is made by throwing spaghetti against walls and seeing what sticks. (More accurately, throwing nucleic acid against harsh reality and seeing what successfully makes more nucleic acid.) We are 3.5 billion years of hacks in fragile trench coats.
    • Scott Star Codex describes the phenomenon in neurotransmitters, but it’s true for all of molecular biology:

You know those stories about clueless old people who get to their Gmail account by typing “Google” into Bing, clicking on Google in the Bing search results, typing “Gmail” into Google, and then clicking on Gmail in the Google search results?

I am reading about serotonin transmission now, and everything in the human brain works on this principle. If your brain needs to downregulate a neurotransmitter, it’ll start by upregulating a completely different neurotransmitter, which upregulates the first neurotransmitter, which hits autoreceptors that downregulate the first neurotransmitter, which then cancel the upregulation, and eventually the neurotransmitter gets downregulated.

Meanwhile, my patients are all like “How come this drug that was supposed to cure my depression is giving me vision problems?” and at least on some level the answer is “how come when Bing is down your grandfather can’t access Gmail?

  • My programming friends tell me that spaghetti towers are near-universal in the codebases of large companies. Where it would theoretically be nice if every function was neatly ordered, but actually, the thing you’re working on has three different dependencies, two of which are unmaintained and were abandoned when the guy who built them went to work at Google, and you can never be 100% certain that your code tweak won’t crash the site.
  • I think this also explains some of why bureaucracies look and act the way they do, and are so hard to change.

I think there are probably a lot of examples of spaghetti towers, and they probably have big ramifications for things like, for instance, what systems evolution can and can’t build.

I want to do a much deeper and more thoughtful analysis about what exactly the implications here are, but this has been kicking around my brain for long enough and all I want to do is get the concept out there.

Does this feel like a meaningful concept? Where do you see spaghetti towers?

Crossposted to LessWrong.


Happy solstice from Eukaryote Writes Blog. Here’s a playlist for you (or listen to Raymond Arnold’s Secular Solstice music.)

Biodiversity for heretics

Epistemic status: Not very confident in my conclusions here. Could be missing big things. Information gained through many hours of reading about somewhat-related topics, and a small few hours of direct research.

Summary: Biodiversity research is popular, but interpretations of it are probably flawed, in that they’re liable to confuse causation and correlation. Biodiversity can be associated with lots of variables that are rarely studied themselves, and one of these, not “biodiversity” in general, might cause an effect. (For example, more biodiverse ecosystems are more likely to include a particular species that has significant effects on its own.) I think “biodiversity” is likely overstudied compared to abundance, biomass, etc., because it’s A) easier to measure and B) holds special and perhaps undue moral consideration.


From what I was told, biodiversity – the number of species present in an environment – always seemed to be kind of magical. Biodiverse ecosystems are more productive, more stable over time, produce higher crop yields, and are more resistant to parasites and invaders. Having biodiversity in one place increases diversity in nearby places, even though diversity isn’t even one thing (forgive me for losing my citation here). Biodiverse microbiomes are healthier for humans. Biodiversity is itself the most important metric of ecosystem health. The property “having a suite of different organisms living in the same place” just seems to have really incredible effects.

First of all – quickly – some of what I was told isn’t actually true. More diverse microbiomes in bodies aren’t always healthier for humans or more stable. The effects of losing species in ecosystems varies a ton. More biodiverse ecosystems don’t necessarily produce more biomass.

That said, there’s still plenty of evidence that biodiversity correlates with something.

But: biodiversity research and its interpretations have problems. Huston (1997) introduced me to a few very concrete ways this can turn up misleading or downright inaccurate results.

Our knowledge about biodiversity’s effects on ecosystems comes from either experiments, in which biodiversity is manipulated in a controlled setting; or in observations of existing ecosystems. Huston identifies a few ways that these have, historically, given us bad or misleading data:

  1. Biotic or abiotic conditions, either in observations or experiments, are altered between groups. (E.g. you pick some sites to study that are less and more biodiverse, but the more-biodiverse sites are that way because they get more rainfall – which obviously is going to have other impacts)
  2. Species representing the “additional biodiversity” in experiments aren’t chosen randomly, they’re known to have some ecosystem function.
  3. Increasing the number of species increases the chance that one or a few of the added species will have some notable ecosystem effect on their own.

I’m really concerned about (3).


To show why, let’s imagine aliens who come to earth and want to study how humans work. They abduct random humans from across the world and put them in groups of various sizes.

Building walls

The aliens notice that the human civilizations have walls. They give their groups of abducted humans blocks and instruct them to build simple walls.

It turns out that larger groups of humans can build, on average, proportionally longer walls. The aliens conclude that wall-building is a property of larger groups of humans.

Building radios

The aliens also notice that human civilizations have radios. They give their groups of abducted humans spare electronic parts, and instruct them to build a radio.

Once again, it turns out that larger groups of humans are proportionally more likely to be able to build a radio. The aliens conclude that radio-building, too, is a property of large groups of humans.


The mistake the aliens are making is in assuming that wall- and radio-building are functions of “the number of humans you have in one place”. More people can build a longer simple wall, because there’s more hands to lift and help. But when it comes to building radios, a larger group just increases the chance that at least one human in the group will be an engineer.

To the aliens, who don’t know about engineers, “number of humans” kind of relates to the thing they’re interested in – they will notice a correlation – but they’re making a mistake by just waving their hands and saying that mostly only large groups of humans possess the intelligence needed to build a radio, perhaps some sort of hivemind.

Similarly, we’d make a mistake by looking at all the strange things that happen in diverse ecosystems, and saying that these are a magical effect that appears whenever you get large numbers of different plants in the same field. I wonder how often we notice that something correlates with “biodiversity” and completely miss the actual mechanism.

Aside from a specific species or couple of species in combination that have a particular powerful effect on ecosystems, what else might biodiversity correlate to that’s more directly relevant? How about abundance (the number of certain organisms of some kind present)? Or biomass (the combined weight of organisms)? Or environmental conditions, like the input of energy? Or the amount of biomass turnover, or the amount of predation, etc., etc.?

I started wondering about this while doing one of my several projects that relate to abundance in nature. We should still study biodiversity, sure. But the degree to which biodiversity has been studied compared to, say, abundance, has lead us to a world where we know there are 6,399 species of mammals, but nobody has any idea – even very roughly – how many mammals there are. Or how we’re pretty sure that there are about 7.7 million species of animals, plus or minus a few hundred thousand, which is a refinement of many previous estimates of the same thing – and then we have about two people (one of whom is wildly underqualified) trying to figure out how many animals there are at all.

It’s improving. A lot of recent work focuses on functional biodiversity. This is the diversity of properties of organisms in an environment. Instead of just recording the number of algae species in a coastal marine shelf, you might notice that some algae crusts on rocks, some forms a tall canopy, some forms a low canopy, and some grows as a mat. It’s a way of separating organisms into niches and into their interactions with the environment.

Functional diversity seems to better describe ecosystem effects than diversity alone (as described e.g. here). That said, it still leaves the door open for (3) – looking at functional diversity means you must know something about the ecosystem, but it’s not enough to tell you what’s causing the effect in and of itself.


To illustrate why:

Every species has some functional properties that separate it from other species – some different interactions, some different niche or physical properties, etc. We can imagine increasing biodiversity, then, as “a big pile of random variables.”

It turns out that when you start with a certain environment and slowly add or remove “a big pile of random variables”, that changes the environment’s properties. Who would have thought?


So is biodiversity instrumentally relevant to humans?

  1. There are sometimes solid explanations for why biodiversity itself might be relevant to ecosystems, e.g. the increased selection for species complementary over time theory.
  2. Biodiversity probably correlates to the things that studies claim it correlates to, including the ones that find significant environmental effects. I just claim that often, biodiversity is plausibly falsely described as the controlling variable rather than one of its correlates. (That said, there are reasons we might expect people to overstate its benefits – read on.)

If this is true, and biodiversity itself isn’t the driving force we make it out to be, why does everyone study it?

Firstly, I think biodiversity is easier to measure than, say, individual properties, or abundance. Looking at the individual properties and traits of each species in the environment is its whole own science, specific to that particular species and that particular environment. It would be a ridiculous amount of work.

But when we try to get the measure of an ecosystem without this really deep knowledge, we turn into the alien scientists – replacing a precise and intricate interaction with a separate but easier-to-measure variable that sort of corresponds with the real one.

What about studying one of the other ecosystem properties, like abundance? I’m guessing that in the modern research environment, you’d basically have to be collecting biodiversity data anyways.

Researcher: We found 255 beetles in this quadrant!

PI: What kind?

Researcher: You know. Beetles.

…And if you’re identifying everything you find in an environment anyways, it’s easier to just keep track of how many different things you find, rather than do that plus exhaustively search for every individual.

This is just speculation, though.

Secondly, a lot of people believe that species and ecosystems are a special moral unit (independent of any effects or benefits they might have on humans). That’s why people worry about losing the parasites of endangered species, or wonder if we shouldn’t damage biodiversity by eradicating diseases.

And… it’s hard to explain why this seems wrong to me, but I’ll try. I get it. Environmentalism is compelling and widespread. It was the background radiation of virtually almost every interaction with nature I had growing up. It was taken for granted that every drop of biodiversity was a jewel with value beyond measure, that endangered species were inherently worth going to great lengths to protect and preserve, that ecosystems are precariously balanced configurations that should be defended as much as possible from encroachment by humans. Under this lens, of course the number of species present is the default measurement – the more biodiversity preserved from human destruction, the more intricate and elaborate the ecosystem (introduced species excepted), the better.

And… doesn’t that seem a little limited? Doesn’t that seem like a sort of arbitrary way to look at huge parts of the world we live in? It’s not worth throwing out, but perhaps it deserves a little questioning. Where else could we draw the moral lines?

Personally, I realized my morality required me to treat animals as moral patients. This started with animals directly used by humans, but then got me re-examining the wild animals I’d been so fond of for so long.

Currently, I put individual animals and species in mostly-separated mental buckets. A species, a particular pattern instantiated by evolution acting on rocks and water over time, is important – but it’s important because it’s beautiful, like a fantastic painting made over decades by a long-dead artist. We value aesthetics, and interpretations, and certainly the world would be worse off without a piece of beauty like this one.

But an individual matters morally because it feels. It cares, it thinks, it feels joy, it suffers. We know because we are one, and because the same circuits and incentives that run in our brains also run in the brains of the cats, chickens, songbirds, insects, earthworms, whale sharks, and bristlemouths that we share this lonely earth with.

We might say that a species “suffers” or “is in pain”, the same way that a city “is in pain”, and we might mean several different things by that. We might say many of the individuals in the collective suffer. Or we might mean that the species is degraded somehow the way art is degraded – lessened in quantity, less likely to survive into the future, changing rapidly, etc. But it seems like a stretch to call that pain, in the way that being eaten alive is pain.

Obviously, at some point, you have to make trade-offs over what you care about. I don’t have my answers worked out yet, but for now, I put a lot more value on the welfare of individual animals than I used to, and I care less about species.

I don’t expect this viewpoint to become widespread any time soon. But I think it’s possible that the important things in nature aren’t the ones we’ve expected, and that under other values, properties like abundance and interactions deserve much more attention (compared to biodiversity) than they have now.


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[OPEN QUESTION] Insect declines: Why aren’t we dead already?

One study on a German nature reserve found insect biomass (e.g., kilograms of insects you’d catch in a net) has declined 75% over the last 27 years. Here’s a good summary that answered some questions I had about the study itself.

Another review study found that, globally, invertebrate (mostly insect) abundance has declined 35% over the last 40 years.

Insects are important, as I’ve been told repeatedly (and written about myself). So this news begs a very important and urgent question:

Why aren’t we all dead yet?

This is an honest question, and I want an answer. (Readers will know I take catastrophic possibilities very seriously.) Insects are among the most numerous animals on earth and central to our ecosystems, food chains, etcetera. 35%+ lower populations are the kind of thing where, if you’d asked me to guess the result in advanced, I would have expected marked effects on ecosystems. By 75% declines – if the German study reflects the rest of the world to any degree – I would have predicted literal global catastrophe.

Yet these declines have been going on for apparently decades apparently consistently, and the biosphere, while not exactly doing great, hasn’t literally exploded.

So what’s the deal? Any ideas?

Speculation/answers welcome in the comments. Try to convey how confident you are and what your sources are, if you refer to any.

(If your answer is “the biosphere has exploded already”, can you explain how, and why that hasn’t changed trends in things like global crop production or human population growth? I believe, and think most other readers will agree, that various parts of ecosystems worldwide are obviously being degraded, but not to the degree that I would expect by drastic global declines in insect numbers (especially compared to other well-understood factors like carbon dioxide emissions or deforestation.) If you have reason to think otherwise, let me know.)


Sidenote: I was going to append this with a similar question about the decline in ocean phytoplankton levels I’d heard about – the news that populations of phytoplankton, the little guys that feed the ocean food chain and make most of the oxygen on earth, have decreased 40% since 1950.

But a better dataset, collected over 80 years with consistent methods, suggests that phytoplankton have actually increased over time. There’s speculation that the appearance of decrease in the other study may have been because they switched measurement methods partway through. An apocalypse for another day! Or hopefully, no other day, ever.


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2 extremely literal introspection techniques

Introspection literally means “to look inside”. Your eye is a camera made of meat – here are two ways to use your eyes to look at their own structure.

The Blue Field Entopic Phenomena

Stare up at a clear blue sky. (If no blue sky is available, for instance, if you’re in Seattle and it’s January, I was able to get a weaker version by putting my face close to this image instead. Your mileage may vary.)

BlueFieldGif

Animation of the phenomena. Made by Wikimedia user Unmismoobjectivo, under a CC BY-SA 3.0 license.

Notice tiny white spots with dark tails darting around your field of vision? You’re looking at your own immune system  – those are white blood cells moving in the capillaries in your retina. Normally transparent, they reflect blue light. The darker tails are build-ups of smaller red blood cells in the narrow capillaries, which are all but blocked by the large white blood cells.

This is clear enough that the speed at which the dots move can be used to accurately measure blood pressure in the retina. To do this, patients compare their blue field entopic phenomena to animated dots moving at various speeds. I wanted to find some calibrated gifs to try this at home, so if you see some, let me know.

On the other hand, if you see things that look like this all the time everywhere, it might be visual snow.

2. The Purkinje Tree

WARNING: A cell phone flashlight probably isn’t strong enough to damage your eyes, but especially if you try this with anything stronger than that, or if you have a condition that would make it very bad to accidentally shine a flashlight in your face, use your own judgement on proceeding.

Stand or lie down in a dark room.

Turn on your phone flashlight or a penlight, and hold it up against the side of your face.

Position yourself so that you’re looking into darkness, and the light beam passes just over the front of your eyes – you’re trying to get light to go across the surface of your pupil, but not directly into your eyes.

You might need to adjust the angle.

What you’re looking for is the Purkinje tree – shadows of the retinal blood vessels cast onto other parts of the retina. It was first seen by legendary Czech anatomist Jan Evangelista Purkynê, who also found Purkinje brain cells, sweat glands, and Purkinje fibers in the heart, and introduced the terms “blood plasma” and “protoplasm”.

YarlungTsangpoRiver.jpg

The Purkinje Tree reminded me of aerial photos of branching riverbeds, as in this NASA photo of the Yarlung Tsangpo River in Tibet. So look for a structure like this.

Once you see it, the image will vanish quickly – your brain already gets an image of the blood vessels on the retina, so it’s used to removing it from your perception and will adapt. If you waggle the light source gently at about one hertz (once per second), the image stays visible.


Happy new year from Eukaryote Writes Blog!

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The children of 3,500,000,000 years of evolution

[NASA image of the winter solstice from space. Found here.]

This is the speech I gave during the “Twilight” portion of Seattle’s 2017 Secular Solstice. See also the incomparable Jai’s speech. A retrospective on our solstice and how we did it coming soon.


Eons ago, perhaps in a volcanic vent in the deep sea, under crushing pressure, in total darkness, chemicals came together in a process that made copies of itself. We’re not exactly sure how this happened – perhaps a simple tangle of molecules grabbed other nearby molecules, and formed them into identical tangles.

You know the story – some of those chemical processes made mistakes along the way. A few of those copies were better at copying themselves, so there were more of them. But some of their copies were subtly different too. And so it goes. This seems straightforward, but this alone is the mechanic of evolution, the root of the tree of life. Everything else follows.

So these tangles of protein or DNA or whatever-it-was in the deep sea, it keeps going. This chemical process grows a cell wall, DNA, a metabolism, starts banding together and eating sunlight.

By this point, the deep-sea vent itself had long since been swallowed up by tectonic plates, the rock recycled into magma beneath the ocean floor. But the process carried on.

Biologists even understand that if you let this process run for long enough, it starts going to war, and paying taxes, and curing diseases, and driving old beat-up cars, and lying awake at night wondering what it means to exist at all.

All of that? Evolution didn’t tell us to do that. Evolution is what gave you a fist-sized ball of neurons, and gave you the tools to reshape those neurons based on what you learned. And you did the rest.

Sure, evolution gave you some other things – hands for grabbing, a voice for communicating, a vague predilection for fat and sugar and other entities who are similar to you. But all of this is the output of a particular process – a long and unlikely chemical process for which you, the building blocks of your brain, your hands, your tastes, are a few of the results. None of this happened on purpose. In the eyes of the evolutionary tree of life, you can’t think about existing ‘for a greater reason’ beyond the result of this process. What would that mean? Does fusion ‘happen on purpose’? Does gravity work ‘for a greater reason’?

This might sound nihilistic. I think this has two lessons for us. First of all, when you and your friends are sitting in a diner eating milkshakes and french fries at 2 AM, as far as evolution gets any say in your life, you’re doing just fine.

But here’s the other thing – we’re a biological process. Apparently, we’re just what happens when you mix rocks and water together and then wait 3.5 billion years. Everything around us today, our lives, our struggles, nobody prepared us for this. It makes sense that there will be times when nothing makes sense. When your body or your brain don’t seem to be enough, well, we weren’t made for anything.

Nobody exists on purpose. There’s no promise that we’ll get to keep existing. There’s no assurance that we, as a species, will be able to solve our problems. Maybe one day we’ll run into something that’s just too big, and the tools evolution gave us won’t enough. It hasn’t happened yet, but what do we know? As far as we’re aware, we’re the only processes in the whole wide night sky that have ever come this far at all. We don’t have the luxury of examples or mentors to look to.

All we have are these tools, this earth, this process, these hands, these minds, each other. Nothing less and nothing more.


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How many neurons are there?

Image from NOAA, in the public domain.

Last updated on March 16, 2018. I just finished a large project trying to estimate that. I’ve posted it on its own page here. Here’s the abstract:

We estimate that there are between 10^23 and 10^24 neurons on earth. Most of this is distributed roughly evenly among small land arthropods, fish, and nematodes, or possibly dominated by nematodes with the other two as significant contenders. For land arthropods, we multiplied the apparent number of animals on earth by mostly springtail-sized animals, with some small percentage being from larger insects modeled as fruit flies. For nematodes, we looked at studies that provide an average number of nematodes per square meter of soil or the ocean floor, and multiplied them by the number of neurons in Caenorhabditis elegans, an average-sized nematode. For fish, we used total estimates of ocean fish biomass, attributed some to species caught by humans, and used two different ways of allocating the remaining biomass. Most other classes of animal contribute 10^22 neurons at most, and so are unlikely to change the final analysis. We neglected a few categories that probably aren’t significant, but could conceivably push the estimate up.

Using a similar but less precise process based on evolutionary history and biomass over time, we also estimate that there have been between 10^32 and 10^33 neuron-years of work over the history of life, with around an order of magnitude of uncertainty.

Evolutionary Innovation as a Global Catastrophic Risk

(This is an extended version of the talk I have at EA Global San Francisco 2017. Long-time readers will recognize it as an updated version of a post I wrote last year. It was wonderful meeting people there!)

graph.png

This is a graph of extinction events over the history of animal life.

There are five canonical major extinction events that have occurred since the evolution of multicellular life. Biotic replacement has been hypothesized as the major mechanism for two of them: the late Devonian extinction and the Permian-Triassic extinction. There are three other major events – the Great Oxygenation Event, End Ediacaran extinction, and the Anthropocene / Quaternary extinction.

Let’s look at four of them. The first actually occurs right before this graph starts.

I decided not to discuss the Great Oxygenation Event in the talk itself, but it’s also an example – photosynthetic cyanobacteria evolved and started pumping oxygen into the atmosphere, which after filling up oxygen sinks in rocks, flooded into the air and poisoned many of the anaerobes, leading to the “oxygen die-off” and the “rusting of the earth.” I excluded it because A) it wasn’t about multicellular life, which, let’s face it, is much more relevant and interesting, and B) I believe it happened over such a long amount of time as to be not worth considering on the same scale as the others.

(I was going to jokingly call these “animal x-risks”, but figured that might confuse people about that the point of the talk was.)

The End-Ediacaran extinction

ediacaran

“Disckonsia Costata” by Verisimilius is licensed under CC BY-SA 3.0

We don’t know much about Precambrian life, but it’s known as the “Garden of Ediacara” and seems to have been a peaceful time.

The Ediacaran sea floor was covered in a mat of algae and bacteria, and ‘critters’ – some were definitely animals, others we’re not sure – ate or lived on the mats. There were tunneling worms, the limpets, some polyps, and the sand-filled curiosities termed “vendozoans”. They may have been single enormous cells like today’s xenophylophores, with the sand giving them structural support. The fiercest animal is described as a “soft limpet” that eats microbes. They don’t seem to have had predators, and this period is sometimes known as the “Garden of Ediacara”. (1)

At 542 million years ago, something happens – the Cambrian explosion. In a very short 5 million years, a variety of animals evolve in a short window.

Molluscs, trilobites and other arthropods, a creative variety of worms eventually including the delightful Hallucigenia, and sponges exploded into the Cambrian. They’re faster and smarter than anything that’s ever existed. The peaceful Ediacaran critters are either outcompeted or gobbled up, and vanish from the fossil record. The first shelled animals indicate that predation had arrived, and that the gates of the Garden of Ediacara had closed forever.

The end-Devonian extinction

Jump forward a few million years – 50% of genuses go extinct. Marine species suffered the most in this event, probably due to anoxia.

There’s an unexpected possible culprit – plants around this time made a few evolutionary leaps that began the first forests. Suddenly a lot of trees pumping oxygen into the air lead to global cooling, and large amounts of soil lead to nutrient-rich runoff, which lead to widespread marine anoxia which decimates the ocean.

devonian

Gingko trees, some of the oldest tree lineages alive. Image by Jean-Pol Grandmont, under a CC BY-SA 3.0 license.

We do know that there were a series of extinction events, so forests were probably only a partial cause. The longer climate trend around the extinction was global warming, so the yo-yoing temperature (from general warming and cooling from plants) likely contributed to extinction. (2) It’s strange to think that the land before 375 million years ago didn’t have much in the way of soil – major root structures contributed to rock wearing away. Plus, once you have some soil, and once the first trees die and contribute their nutrients, you get more soil and more plants – a positive feedback loop.

The specific trifecta of evolutions that let forests take over land: significant root structures, complex vascular systems, and seeds. Plants prior to this were small, lichen-like, and had to reproduce in water. (3)

The Permian-Triassic extinction

96% of marine species go extinct. Most of this happens in a 20,000 year window, which is nothing in geologic time. This is the largest and most sudden prehistoric extinction known.

The cause of this one was confusing for a long time. We know the earth got warmer, or maybe cooler, and that volcanoes were going off, but the timing didn’t quite match up.

Volcanoes were going off for much longer than the extinction, and it looks like die-offs were happening faster than we’d expect from increasing volcanism, or standard climate change cycles. (4) One theory points out that die-offs line up with exponential or super-exponential growth, as in, from a replicating microbe. Remember high school biology?

One theory suggests Methanosarcina, an archaea that evolved the chemical process that turned organic carbon into methane around the same time. Remember those volcanoes? They were spewing enormous amounts of nickel – an important co-factor for that process.

permiantriassic

Methanosarcina, image from Nature

(Methanosarcina appeared to have gotten the gene from a cellulose-digesting bacteria – definitely a neat trick. (5) )

The theory goes that Methanosarcina picked up its new pathway, and flooded the atmosphere with methane, which raised the surface temperature of the oceans to 45 degrees Celsius and killed most life. (2)

This report is a little recent, and it’s certainly unique, so I don’t want to claim that it’s definitely confirmed, or sure on the same level that, say, the Chicxulub impact theory is confirmed. That said, at the time of this writing, the cause of the Permian-Triassic extinction is unclear, and the methanogen theory doesn’t seem to have been majorly criticized or debunked.

Quaternary and Anthropocene extinctions

Finally, I’m going to combine the Quaternary and Anthropocene events. They don’t show up on this chart because the data’s still coming in, but you know the story – maybe you’re an ice-age megafauna, or rainforest amphibian, and you are having a perfectly fine time, until these pretentious monkeys just walk out of the Rift Valley, and turn you into a steak or a corn farm.

anthropocene

Art by Heinrich Harder.

Because of humans, since 1900, extinctions have been happening at about a thousand times the background rate.

(Looking at the original chart, you might notice that the “background” number of extinctions appears to be declining over time – what’s with that? Probably nothing cosmic – more recent species are just more likely to survive to the present day.)

Impacts from evolutionary innovation

You can probably see a common thread by now. These extinctions were caused – at least in part – by natural selection stumbling upon an unusually successful strategy. Changing external conditions, like nickel from volcanoes or other climate change, might contribute by giving an edge to a new adaptation.

    1. In some cases, something evolved that directly competed the others – biotic replacement
    2. In others, something evolved that changed the atmosphere.
    3. I’m going to throw in one more – that any time a species goes extinct due to a new disease, that’s also an evolutionary innovation. Now, as far as we can tell, this is extremely rare in nature, but possible. (7)

Are humans at risk from this?

From natural risk? It seems unlikely. These events are rare and can take on the order of thousands of years or more to unfold, at which point we’d likely be able to do something about it.

That is, as far as we know – the fossil record is spotty. As far as I can tell, we were able to pin the worst of the Permian-Triassic extinction down to 20,000 years only because that’s how narrow the resolution on the fossil band formed at the time was. It might have actually been quicker.

Even determining if an extinction has happened or not, or if the rock just happened to become less good at holding fossils, is a struggle. I liked this paper not really for the details of extinction events (I don’t think the “mass extinctions are periodic” idea is used these days), but for the nitty gritty details of how to pull detailed data out of rocks.

That said, for calibrating your understanding, it seems possible that extinctions from evolutionary innovation are more common than mass extinctions involving asteroids (only one mass extinction has been solidly attributed to an asteroid: the Chicxulub impact that ended the reign of dinosaurs.) That’s not to say large asteroid impacts (bolides) don’t cause smaller extinctions – but one source estimated the bolide:extinction ratio to be 175:1. (2)

Plus, having a brain matters, and I think I can say it’s really unlikely that a better predator (or a new kind of plant) is going to evolve without us noticing. There are some parallels here with, say, artificial intelligence risk, but I think the connection is tenuous enough that it might not be useful.

If we learn that such an event is happening, it’s not clear what we’d do – it depends on specifics.

Synthetic biology

But consider synthetic biology – the thing where we design new organisms and see what happens. As capabilities expand, should we worry about lab escapes on an existential scale? I mean, it has happened in nature.

Evolution has spent billions of years trying to design better and better replicators. And yet, evolutionary innovation catastrophes are still pretty rare.

That said, people have a couple of advantages:

        1. We can do things on purpose. (I mean, a human working on this might not be trying to make a catastrophic geoweapon – but they might still be trying to make a really good replicator.)
        2. We can come up with entirely new things. When natural selection innovates, every incremental step on the way to the final result has to an improvement on what came before. It’s like if you tried to build a footbridge, but at every single step of building it, it had to support more weight than before. We don’t have those constraints – we can just design a bridge and then build it and then have people walk across it. We can design biological systems that nobody has seen before.

This question of if we can design organisms more effective than evolution is still open, and crucial for telling us how concerned we should be about synthetic organisms in the environment.

People are concerned about synthetic biology and the risk of organisms “escaping” from a lab, industrial setting, or medical setting into the environment, and perhaps persisting or causing local damage. They just don’t seem to be worried on an existential level. I’m not sure if they should be, but it seems like the possibility is worth considering.

For instance, a company once almost released large quantities of an engineered bacteria that turned out to produce soil ethanol in large enough quantities to kill all plants in a lab microcosm. It appears that we don’t have reason to think it would have outcompeted other soil biota and actually caused an existential or even a local catastrophe, but it was caught at the last minute and the implications are clearly troubling. (9)


  1. Ediacaran biota: The dawn of animal life in the shadow of giant protists
  2. On the causes of mass extinctions
  3. Terrestrial-Marine Teleconnections in the Devonian: Links between the Evolution of Land Plants, Weathering Processes, and Marine Anoxic Events
  4. The Permo-Triassic extinction
  5. Methanogenic burst in the End-Permian carbon cycle
  6. Natural Die-offs of Large Mammals: Implications for Conservation I’m pretty sure I’ve seen at least a couple other sources mention this, but can’t find them right now. I had Chytridiomycosis in mind as well. This seems like an important research project and obviously has some implications for, say, biology existential risk.
  7. Rather sensationalized description from Cracked.Com

Beespotting on I-5 and the animal welfare approach to honey

The drive from Seattle to San Francisco along I-5 is a 720-mile panorama of changing biomes. Forest, farmland, and the occasional big city get very gradually drier, sparser, flatter. You pass a sign for the 45th parallel, marking equidistance between the equator and the North Pole. Then the road clogs with semis chugging their way up big craggy hills, up and up, and then you switch your foot from the gas to the brake and drop down the hills into more swathes of farmland, and more intense desert, with only the very occasional tiny town to get gas and bottles of cold water. Eventually, amid the dry hills, you see the first alien tower of a palm tree, and you know the desert is going to break soon.

Of course, I like the narrative arc on the drive back even better. Leaving Berkeley in the morning, you hit the desert in its element – bright and dry – without being too hot. That comes later, amid the rows and rows of fruit and nut trees, which turns into the mountains again, and into the land on the side of the mountains, now dominated by lower bushy produce crops and acres of flat grain land. You pass a sign for Lynn County, the Grass Seed Capital of the US. Finally, well into dusk, you hit the Washington border, and the first rain you’ve seen on the entire trip starts falling right on cue. Then you meet some friends in your old college town for a quick sandwich and tomato soup at 11:30 PM, and everything is set right with the world, letting you arrive back home by an exhausted but satisfied 1:30 AM.

I like this drive for giving a city kid a slice of agriculture. I’ve written about the temporal scale of developments in agriculture, but the spatial scale is just as incredible. About 50% of land in the US is agricultural. Growing the calorie-dense organisms that end up on my plate, or fueling someone’s car, or exported onto someone else’s plate, or someone else’s feedbag, is the result of an extraordinary amount of work and effort.

I talked about the plants – there’s trees for fruit and nuts, vines, grain, corn, a million kinds of produce. I only assume this gets more impressive when you go south from San Francisco. (In recent memory, I’ve only visited as far south as Palo Alto, and was shocked to discover a lemon tree. With lemons on it! In December! Who knew? Probably a lot of you.)

There’s also animals – aside from a half dozen alpacas and a few dozen horses, you spot many sheep and many, many cows from the highway. The cattle ranches were quite pretty and spacious – I wonder if this is luck, or if there’s some kind of effort to put the most attractive ranches close to the highway. Apparently there are actual feedlots along I-5 if you keep going south. I certainly didn’t notice any happy chicken farms along the way.

And then there are the bees.

I.

Bees are humanity’s most numerous domesticated animal. You don’t see them, per se, since they are, well, bees. What you can see are the hives – stacks of white boxes like lost dresser drawers congregating in fields. Each box contains the life’s work of a colony of about 19,200 bees.

800px-osman_bey_ve_arc4b1larc4b1

I forgot to start taking photos until it was already dark out, so here are some Wikimedia photos instead. If you want me to take more photos, feel free to ask for my paypal to fund me making the drive again. 😛 | Photo by Fahih Sahiner, CC BY-SA 4.0

The boxes look like this. The bees look like this.

Bees are enormously complicated and fascinating insects. They live in the densely packed hives described above, receiving chemical instructions by one breeding queen, and eusocially supporting her eggs that become the next generation of the hive. In the morning, individual bees leave the hive, fly around, and search for pollen sources, which they shove into pouches on their legs. Returning, if they’ve located a juicy pollen source, they describe it to other bees using an intricate physical code known as the waggle dance.

waggle_diagram

Waggle dance patterns performed by the worker bees. | North Carolina State Extension publications.

What images of this don’t clearly show is that in normal circumstances, this is done inside the hive, under complete darkness, surrounded by other bees who follow it with their antennae.

The gathered pollen is used to sustain the existing bees, and, of course, create honey – the sugar-rich substance that feeds the young bee larvae and the hive through winter. Each “drawer” of the modern Langstroth beehive – seen above – contains ten wooden frames, each filled in by the bees with a wax comb dripping with honey. At harvesting time, each frame is removed from the hive, the carefully placed wax caps covering each honey-filled comb are broken off, and the honey is extracted via centrifuge. (More on the harvesting practice.)

Each beehive makes about 25 pounds of harvestable honey in a season, and each pound of honey represents 55,000 miles flown by bees. Given the immense amount of animal labor put into this food, I want to investigate the claim that purchasing honey is a good thing from an animal welfare perspective.

I’m not about to say that people who care about animal welfare should be fine eating honey because bees don’t have moral worth, because I suspect that’s not true. I suspect that bees can and do suffer, and at the very least, that we should consider that they might. The capacity to suffer is evolutionary – it’s an incentive to flee from danger, learn from mistakes, and keep yourself safe when damaged. Bees have a large capacity to learn, remember, and exhibit altered behavior when distressed.

Like other social insects, however, bees also do a few things that contraindicate suffering in most senses, like voluntarily stinging invaders in a way that tears out some internal organs and leaves them at high risk of death. In addition, insects possibly don’t feel pain at the site of an injury (though I’m not sure how well studied this is over all insects) (more details). They may feel some kind of negative affect distinct from typical human pain. In any case, it seems like bee welfare is possibly important, and since there are 344,000,000,000,000 of them under our direct care, I’m inclined to err on the side of “being nice to them” lest we ignore an ongoing moral catastrophe just because we didn’t think we had incontrovertible proof at the time.

This is harder than it sounds, because of the almonds.

II.

The beehives I saw on on I-5 don’t live there full-time. They’re there because of migratory beekeepers, who load hives into trucks and drive them all over the country to different fields of different crops. As we were all told in 3rd grade, bees are important pollinators, and while the fields of old were pollinated with a mix of wild insects and individually-managed hives, like other animal agriculture, the bees of today are managed on an industrial scale.

(We passed at least one truck that was mostly covered with a tarp, but had distinctive white boxes visible in the corners. I’m pretty sure that truck was full of bees.)

60-75% of the US’s commercial hives congregate around Valentine’s Day in the middle of California to pollinate almonds. When we say bees are important pollinators, one instance of this is that almonds are entirely dependent on bees – every single almond is the result of an almond tree flower pollinated by a bee. California grows 82% of the world’s almonds.

According to this Cornell University report, honeybees in the US provide:

  • 100% of almond pollination.
  • 90% of apple, avocado, blueberry, cranberry, asparagus, broccoli, carrot, cauliflower, onion, vegetable seed, legume seed, rapeseed, and sunflower pollination.
  • 80%+ of  cherry, kiwifruit, macadamia nut, celery, and cucumber pollination
  • 70%+ of grapefruit, cantaloupe, and honeydew pollination.
  • 60%+ of pear, plum, apricot, watermelon, and alfalfa seed and hay (a major food source for cattle) pollination.
  • 40%+ of tangerine, nectarine, and peach pollination.
  • 5-40% of pollination for quite a few other crops.

Our agricultural system, and by extension, the food you eat is, in huge part, powered by those 344 trillion bees. Much of this bee power is provided by migratory beekeepers. In total, beekeepers in the US make about 30% of their money from honey, and 70% from renting out their bees for pollination.

Sidenote: All of the honey bees kept in the US are one species. (There are also 3000 wild bee species, as well as wild honey bees.) So we’re putting all of our faith in them. If you haven’t been living under a rock for the last decade, you may have heard of colony collapse disorder, which I’d wager is the kind of thing that becomes both more likely and more catastrophic when your system is built on an overburdened monoculture.

III.

Does this mean you actively should eat honey? I really don’t know enough about economics to say that or not. If you’re averse to using animal products, I don’t believe you’re obligated to eat honey – there are many delicious products that do what honey does, from plain sugar to maple syrup to agave to vegan honey.

But if you don’t eat honey and tell other people not to eat honey, I imagine you’re doing that because of a belief that this will lead to fewer bees being brought into existence and used by humans. And if you have this belief that it’s better to have fewer bees used by humans, I’m very curious what you think they’ll be replaced with.

What if you want to reduce the amount of suffering comprised by honeybees in your diet, or in agriculture in general?

One thing people have thought of is encouraging pollination by wild bees and other insects. When thinking about the volume of honeybees you’d need to replace, though, you start to encounter real ethical questions about the welfare of those wild bees. Living in the wild as an insect is plausibly pretty nasty. (I don’t have the evidence either way on whether honey bees or wild bees have better lives – but that if you care about honey bees anyway, it bears considering that this would require humans replacing the huge number of honey bees with other life forms, and that the fact that they’d be living on their own in hedges next to a field, rather than in a wooden hive, doesn’t automatically mean they’ll be happier.)

In addition, scaling up wild pollinators to the scale that would be needed by commercial agriculture would be difficult. Possible, but a very hard problem.

You could eat crops that aren’t mostly pollinated by honeybees. This page lists some – a lot of vegetables make the list. Grains, cereals, and grasses also tend be wind-pollinated.

Beekeeping seems like it might be better than increasing the number of wild pollinators, but migratory beekeeping as a practice reduces bee lifespans, and increases stress markers and parasites compared to stationary hives. Reducing the amount of travel modern hives do might be helpful. Maybe we could just stop growing almonds?

(Although that still leaves us with the problem of apple, asparagus, avocado, blueberry, broccoli, carrot, cauliflower, cranberry, carrot, onions, rapeseed, sunflowers, vegetable seeds, legume seeds, rapeseed, sunflowers…)

It also seems completely possible to raise beehives that are only used for pollination and not honey. This still requires animal labor and more individual bees, but the bees would have less stressful lives.

Or look into robot pollinators.

None of these ideas feel satisfactory, though. I feel like we’ve made our nest of bees and now we have to sleep in it. Any ideas?

beehives_on_the_road

Truck full of beehives. | Photo by Wendy Seltzer. CC BY 2.0.

(Note: I’m aware that this piece is very US-centric. I’m not sure what the bee situation is other countries is like.)

My research on Sentience Politics & metablogging

Stygiomedusa gigantea was discovered around Antarctica, and has been spotted about once per year over the past century. It’s one meter in diameter, and its tentacles are up to 10 meters long. It’s apparently sometimes known as the “guardian of the underworld”. Image from a Monterey Bay Aquarium Research Institute ROV.


I wrote two research summaries for the organization Sentience Politics.

How many wild animals are there?

Which invertebrate species feel pain?

The Sentience Politics research agenda (plus supplementary documents for my pieces) is here.

Sentience Politics describes itself: “Sentience Politics is an antispeciesist political think tank. We advocate for a society in which the interests of all sentient beings are considered, regardless of their species membership, and we rigorously analyze the evidence to assess and pursue the most effective ways to help all sentient beings. Among other activities, we organize political initiatives, publish scientific policy papers, and host conferences to bring forward-thinking minds together to address the major sources of suffering in the world.” I think their work is valuable and recommend checking them out.


Metablogging

You may not be aware that I have an about page. If you want to commission me to do some research for you, or have suggestions for future posts, let me know.

If anyone has suggestions for ways to make an online dichotomous key, let me know. (Workflowy has been suggested, but I don’t think it’s flexible enough to make a nice-looking large dichotomous key with a lot of options.)

I’m planning on looking through old posts and updating them factually, or at least adding a disclaimer on top to reflect any information I no longer suspect is accurate.