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Cross-posted from my blog.

As an EA organizer when I was a grad student at Harvard, I developed an implicit model of community organizing at a university that is complimentary to the funnel model of Center for Effective Altruism (CEA) that was super popular a few years ago. I call mine “optimizing the seed:pollen ratio”. I’m not going to justify outreach as a strategy or advocate for any specific means of outreach—the point is to share my model of outreach efficacy. It’s a fun bonus that my model is well-explained by analogy to a biology concept, which I hope to explain well as a secondary objective.

The funnel model

CEA says, “We are trying to build a community, and one aspect of this project is encouraging people to become more deeply engaged with the community. The funnel metaphor helps us to think about the appropriate goals and audiences for our different projects.” The funnel model is focused on the deliberate composition of the community— how many people are entering the funnel, and what share of the community is at what part of the funnel at any given time. It also suggests that movement through the funnel happens in stages, from outer to middle to core, and there’s both investment from the community at every stage and friction to progressing from one stage to another.

When this model was getting a lot of buzz, there were many discussions about what part of the funnel to be focusing on. This was happening during CEA’s big pivot toward endorsing longtermism as a fundamental tenet of EA. With that, many were arguing that there should much more focus on core EAs and the core-EA-development-pipeline, and much less emphasis on the mid- to casual level of community involvement, because most of the value of EA in the long run will be “in the tails” of the distribution, from original work, not from safer but lower value bets like getting average individuals to donate money. This view basically won and is dominant in EA today.

Seed:pollen ratio



Now for an interlude on plant reproductive strategies.1 This^ is called a “perfect flower” because it has both male and female reproductive organs. The female reproductive organ is the carpal, and it makes seeds. The male reproductive organs are the anthers and they contain pollen. Seeds are larger and contain cytoplasm, the organelles mitochondria and chloroplasts, and a reserve of nutrients. Pollen is much smaller per grain and, like sperm, basically only contains chromosomes. Whereas seeds can be as big as a coconut (which is a seed!), the biggest pollen grains are only 2.5mm long. In terms of energy and resources, seeds are much more costly and pollen is much cheaper.

You may be familiar with human evolutionary psychology ideas about male vs. female reproductive strategies. What’s interesting about hermaphroditic plant species is that individuals are not committed to one strategy or the other, but can vary the amount of investment they put into seeds vs. pollen, either over evolutionary time or as a plastic response to environmental conditions. Per expected offspring, seeds are a safer bet. The average seed is FAR more likely to grow into a plant than the average pollen grain, which makes sense because pollen outnumbers seeds by a factor of 100-1000x (depending on the species— this number is for Cannabis sativa, because for some reason it’s very easy to get estimates of these quantities online for Cannabis :P) But you can make a LOT of pollen for the cost of one seed. Pollen can be carried by pollinators or the wind (or a number of other clever strategies) to sometimes vast distances (a genetically modified pollen grain fertilized a grass seed 21 kilometers away, using nothing but the wind to get there!). The overwhelming majority of pollen grains will not fertilize ovules, but that’s okay because each grain is so cheap that the plant can afford thousands to millions of grains to release.

(Source) How pollen disperses over distance in a species of palm. These observations were made when pollen landed on ovules, so these are observations of pollen success. Look familiar?

The optimal ratio of seeds:pollen is not set in stone

The optimal ratio of seeds:pollen is not set in stone. It depends on the environment, what other species are doing, and on what the other members of your population are doing.2 3 If, for example, your species is being domesticated and humans are assisting in pollination, it behooves every individual to invest less in pollen and more in seeds. If everyone’s making a lot of seeds, then the plant that makes mostly pollen is going to make bank. If everyone’s making mostly pollen, then making extra pollen is going to have vanishing low marginal returns and any extra seeds that get made will almost certainly be fertilized, resulting in a whole new offspring. Some species also have conditional strategies, where the investment in pollen vs. seeds depends on the quality of that individual, so depending on how well they can utilize seeds vs. pollen.4

Optimizing seed:pollen ratio in EA outreach

So, I have a certain energy budget for having EA impact through organizing. I can invest that energy in a small number of individuals who I think will yield high returns by having high impact themselves. The quality time I invest in particular people is my “seeds”. But I also throw a lot of stuff out there just in case it will stick, like when I give a presentation to a large general audience or write blog posts. This (relatively) lower (per listener) investment, higher-reach material is my “pollen”.

Whereas the funnel model invites us to ask how wide we should open the funnel and how to advance people along the funnel, the seed:pollen ratio model allows us to intuitively weigh different levels of investment, different levels of reach, and the distribution of effects that each type of investment—whether closer to seed or to pollen—is likely to have.

My model of impact from EA organizing at Harvard was always dominated by the expected value of core EAs who took on EA as a deep part of their own morality, philosophy, and life plan. But you can’t only focus on making core EAs, because it’s not cut-and-dried how to make lasting, committed EAs. Focusing only on developing core EA candidates is like making only seeds. In biology, we would call this a “pollen-limited” strategy— when it comes down to it, you have to wait for the right serendipitous unknown factors to come along and fertilize your seeds. It’s possible a lot of your seeds will go unfertilized.

Sometimes pollen-style outreach brings in new people who will, with the support of the community, become core EAs or middle-of-the-funnel EAs— it was something like a talk or a blog post or a social media mention of EA that initially brought almost all early core EAs to the community. Sometimes we get lucky5 and people who get the lightest exposure to EA concepts from outreach go and recapitulate the whole set of ideas themselves and have a huge impact without much additional investment from the community. There are lots of fully-formed seeds out there that only need a tiny grain of pollen from us to be fertilized and grow! EAs recognize the importance of tail effects in evaluating expected value. It’s kind of our thing. We should be applying this thinking to building our community. Personally, I think the current approach in the core community is too heavily weighted towards talent searches to try to “pick winners” (seeds) and invest all of our resources in them. IMO we’re leaving valuable pollen opportunities on the table when we don’t make ourselves more legible and accessible to a wide audience, and, though that strategy comes with other trade-offs6, at this time I think we should tip more in that direction.

But whenever you’re reading this and whatever the situation there, I hope that the seed-pollen ratio analogy can be quick and intuitive model to help you improve your reproductive fitness ;)

(Standard disclaimer.)


I am going to make so many generalizations and oversimplifications here. I’m compressing a lot of terminology, for ease, and I’m not including any of the caveats about how much all of this stuff varies by species. Technically what I’m calling a “seed” here is an ovule.


One of my favorite demonstrations of this is a super cool case of genetic conflict. Mitochondria, as I said above, are only transferred in the seed and not the pollen grain. Also, making pollen grains is more taxing on the mitochondria than making eggs, such that plants with sluggish enough mitochondria can’t produce pollen at all. But being lazy kind of works out for the mitochondria in this case, because the energy the plant isn’t spending on pollen goes into more seeds, which will inherit more mitochondria. So you can get into these conflict dynamics where the nuclear genome will evolve repressors of the mitochondrial effect, because it wants to put the seed:pollen ratio in a place that’s good for overall organismal reproductive fitness, which means getting those cheap packets of DNA on the wind. And then the mitochondria evolve a countermove, etc. This may even be one origin of the very common system in plants of having either female plants or hermaphrodites but not male plants. See Chapter 5 of this amazing textbook for more.


To take a more general example about reproductive energy tradeoffs in general, you may have heard that it’s not good to have male marijuana plants (marijuana has separate male and female plants, unlike the hermaphroditic flower shown above) around female plants you intend to harvest. This is because the longer a female plant is “virgin”, the larger its flowers it will grow. It’s a conditional response that’s meant to increase the odds of being fertilized in a low pollen environment. Why not just always have larger female flowers? Because if fertilization had been easier, that extra energy would have been wasted. The starting flower size was set by lots of past plants who struck a good balance.


This phenomenon is best known in mammals as the Trivers-Willard effect, but in that case it pertains to the sex ratio of offspring. The prediction is that, when females are in better condition, they evolve to be more likely to have sons, because a high quality male (like pollen) can have a huge amount of offspring. Females in poor condition should favor daughters, because most females have an intermediate level of reproductive success with much more assurance of reproducing at all (like seeds).


More reliably, pollen-style outreach has many small effects on lots of people, such as making them think more economically about welfare or raising the percentage of their income that seems reasonable to donate to charity in their mind or making “Effective Altruism” seem like a more normal, established position to be reckoned with. I think these benefits of increasingly familiarity with EA values and moving the Overton window are severely undervalued by the EA community right now, but this argument is separate from the one I’m making in the main text.


In particular, if worrying about how to explain EA ideas or feeling pressure have socially desirable views compromises the quality of EA thought, that’s a strong reason not to do pollen-style mass broadcast outreach, even if there are many potential seeds out there who could be reached that way.





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I liked the analogy, thanks!

I would be happy to see more work trying to determine whether the seed-pollen ratio is below or above the optimal, based on empirical data and an explicit model of movement building (e.g. building on Owen Cotton-Barratt's model). Intuitions of people involved in movement building would probably be a key input to such work.

See Chapter 5 of this amazing textbook for more.

This link takes me to an error 404 page.

I'm assuming from the url and https://roberttrivers.com/Books.html that this is supposed to go here: Burt and Trivers' Genes in Conflict: The Biology of Selfish Genetic Elements.

Huh, I’ll try to fix that. Yes, it’s a pdf of the book on Robert Trivers’s Research Gate page.

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