My interview with Red Ice Radio on Smart and SeXy

Listen to the whole thing here. You can get a copy of the book here. Additional reviews and excerpts can be found here. Here is a summary of the first hour:

Roderick joins us for an eye-opening conversation on the biological differences between men and women. After a lighthearted rumination on International Women’s Day, we dive into the main topic of the show. Roderick explains that most scientists are aware of racial and sexual differences, but choose to keep quiet for the sake of their careers. Next, we discuss anthropologist Melvin Konner’s assertion that maleness is a defect – an absurd claim, to be sure, which Roderick easily refutes. We then discuss the discrimination hypothesis. Roderick argues that it is biological differences, not discrimination, that results in different outcomes for men and women. The first hour covers much more, including male-female differences in intelligence, transgenderism, and homosexuality.

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Trump panders to feminists.

Trump signs two laws which create programs promoting STEM disciplines to girls.

“It’s not fair and it’s not even smart,” Trump said of the low percentage of women with STEM degrees who actually work in the field. About a quarter of the women with STEM degrees work in the field.


The topic of women in tech has grown more heated over the past few years. Although women account for about 47 percent of the workforce in the US, according to the Bureau of Labor Statistics, they make up only 25.6 percent of computer and mathematical occupations, and 15.4 percent of architecture and engineering occupations. These days, women earn only 18 percent of computer science degrees. Meanwhile, President Barack Obama‘s administration projected there were more than a half million open jobs in information technology.

Trump signed the bills surrounded by various women like Rep. Barbara Comstock, who introduced the INSPIRE Act, and Sen. Heidi Heitkamp, as well as his daughter Ivanka Trump and First Lady Melania Trump. Vice President Mike Pence was also on hand, along with Texas Rep. Lamar Smith, to name a few.

“That’s really going to be addressed by my administration over the years with more and more of these bills coming out and address the barriers faced by female entrepreneurs and by those in STEM fields,” he said.

Sorry Mr. “suddenly progressive” Trump, it is completely fair that there are not as many women in high IQ fields (and other fields). And there is decades of research indicating exactly why that is. So now he is going to double-down on promoting women in stem, who aren’t suited for it, there by wasting who knows how many millions of taxpayer dollars. Not to mention this will also likely result in more support for wasteful affirmative action which will both make American companies less competitive and make it more difficult for talented men to just get along with making their contributions to society. For anyone who thought Trump was actually going to Make America Great Again, you can rest “easier” knowing that the progressive Cthulhu is still swimming left just as determinedly as it ever was.

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Autism and the Extreme male brain

A new excerpt from my book, Smart and SeXy has been published on

Increased fetal testosterone affects brain morphology, which results in increasing sexual dimorphism in a variety of brain regions. Excessive testosterone triggers super-normal male-typical development of the brain. This hypothesis is consistent with the fact that ASCs have a heavy male bias. It is theoretically easier to transition from normal male testosterone levels to excessive levels than it is to go from normally low levels in females to excessive levels. Further evidence for this theory includes recent research showing that women with Polycystic Ovary Syndrome, a condition which leads to elevated levels of Androgens in the fetal environment, have a 59% increase in the risk of having children with an ASC.i In support of this idea, in traditional autism, the gender disparity ranges from 4:1 to 8:1 male to female sufferers depending on the study. For Asperger’s specifically, the ratio may be as high as 11:1.

Read the rest at

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Smart and SeXy links

This post is stickied, scroll down for most recent post.

Smart and sexy is the definitive book on sex differences in intelligence. With over 300 citations of peer reviewed scientific articles, it describes the latest science on cognitive differences in the sexes without being hampered by political correctness or feminism. Reviews and excerpts are included below.

Original Announcement.


Paperback and E-book


My podcast interview with Red Ice Radio


Counter Currents: Why most high achievers are men [Deutsche Fassung]

Amerika [Also take a look at my interview with Brett Stevens.]


Pseudo-science and bias in the academic establishment

Autism and the extreme male brain

Related Blog posts[Similar to book content, but not as detailed]:

Career women are dysgenic and How standardized testing undervalues men

Please also stop by reddit and subscribe to /r/darkenlightenment and /r/thedailymoldbug. Follow me on twitter and Gab. You can email me at Atavisionary AT gmail DOT com

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“Do you have any advice on writing a controversial, non-fiction book?”

I had a reader send me a message about book writing after he purchased and read my recently released book, Smart and Sexy: The Evolutionary Origins and Biological Underpinnings of Cognitive Differences Between the Sexes:

Dear Sir

Surely you get a lot of correspondence such as this, so hopefully you won’t mind if I begin by thanking you for your book (I wrote the first review on [trademarked website name]) and for the subreddit. It was good to find a place where the rationalism that breaks the taboos of Western society is not tainted by the emotional vitriol of simple hatred or conspiratorial explanations.

If you are willing to offer me some advice with regards to writing a non-fiction book it would be gratefully received. I am not an academic, so I could not hope to write something similar to your work. However I wonder if I might publish a shorter work perhaps of a similar length and style to ‘The Manipulated Man’.

Having looked into publishing non-fiction a year ago, the advice seemed to be consistent: Write a book proposal, find an agent interested, hope they find a publisher. Agents are looking for accredited academics, or public personas with a media presence, willing to endure media appearances to promote the book. None of these things applied or appealed to me. I certainly did not want to be the regressive left’s piñata.

I was aware that there would be no money in writing the book, and given the controversial flavor the truth has these days I saw no personal benefit alongside a fair degree of personal risk. Knowing the West cannot be saved as the values it defines itself by are what has caused its downfall, I thought there was little point attempting to publish a book that no one would read, that would change nothing, and many might hate me for writing.

Circumstances have changed for me in the last year, and having read your book I would like to contribute a work that might be of use for people and civilizations that come after me.

It is always nice to be appreciated.

He has given me some more specific details in later messages and we have been having an on-going conversation. That isn’t so relevant in general. However, I think that sharing my experience in a general way might be helpful for others considering whether or not to commit to a big project like writing a book. Here is my generalized response with respect to my experience with writing a non-fiction book:

As far as my own experience, I don’t think it was typical. I will elaborate a bit, but your mileage may vary. You might also look through my interview with since I talked about my experience and motivation there too.

I am not, nor have I ever intended to be, a professional writer. Life is funny sometimes. I intentionally took the bare minimum of English or writing classes needed for my degree, which if memory serves is a total of 2. Freshman and sophomore English. This has a strong bearing on how valuable or necessary these sorts of classes are. Probably not very. Obviously, there is an innate IQ threshold that comes first, but given that practice makes perfect. In my experience, getting better at writing is mostly about practice with reading and writing. Commenting on reddit was where I got most of my practice with writing. Reading requires finding and reading good writers. If you are smart, you will know them when you see them. (At the risk of sounding cliched, I actually really love the style of writing in books, fiction and non-fiction, from the 1800s and early 1900s. There is a quality of style in there that is absent today).

The book was a work of passion that I felt needed to be made and I was doubtful anyone else would take the time to do it. In the beginning it was nothing more than a slowly increasing collection of notes and citations used to argue with people on the internet. It wasn’t until it really started to grow that I seriously considered turning it into a book. Once I decided this, I more consciously started collecting data and citations.

Early versions of the “book” were nothing more than (1) comments I had written, mostly on reddit, that were related to the topic, (2) Study information (titles, authors, journals) that I wanted to read that I thought might be relevant and (3) bullet point notes from studies I had read completely and listed what I thought was important. As I went through (2) to generate more (3), I usually got anywhere from 5-15 more studies at stage (2) for each one study I took notes on and got to stage (3). Every study was like going down the rabbit hole in Alice in wonderland. Each one was a real chore in and of itself, and it was very daunting to think about how many more needed to be read both with certainty and in potentiality based on previous expansion rates.  I persevered, however, and after years of effort finally got all the studies at stage (3) because over time I eventually got every useful one listed.

I won’t lie, this was a very, very time consuming process and I don’t believe I ever want to do it again. Thinking back, I am still a little amazed I was able to stick it out. It takes a lot of dedication to go through. Fortunately, what most people wish to write probably won’t require anywhere near this level of research (300 or so peer reviewed science papers) so I wouldn’t get too hung up about that. This was probably very particular to this and only this book.

At this point, I launched wholeheartedly into (4) the “conversion” phase as I like to call it. Basically, in order to be a book, all the randomly organized data, commentary, thoughts, what have you, has to be written as a flowing narrative from beginning to end. Narrative isn’t exactly the right word since that has more to do with fiction, but it conveys my meaning here suitably well. Going from A to B to C had to make sense and feel natural. Comments and posts had to be rewritten or adjusted to fit in with the structure, bullet point data had to be pulled together based on topic, bullet point data then had to be written in sentence/paragraph/section form, transitions from one topic to another had to be smoothed over, and even the order of different topics had to be considered strategically. Several whole sections were moved around as this process went forward and I realized better organization structures.

Keep in mind that (1), (2), (3) and (4) were all happening pretty much at every point except in the very beginning and the very end. The relative focus on each one adjusted over time from almost 100% (2) and (3) to 100% (4) with (1) just happening randomly here and there based on my mood and morons to argue with. Morons are very, very helpful for providing motivation to work. They are the secret sauce that pushes you forward. If you want to write something, I highly suggest finding a topic that people are commonly wrong about and willing to engage you on. It is a helpful trick to convert the resulting conversations and research into a book. They also might inspire you (because you want to prove them wrong so bad) to go down a research avenue you wouldn’t have considered otherwise.

I found the division into stages of completion to be very useful to actually getting things done. It was psychologically very helpful to know and feel that I had “completed” something, even if only a small part of one stage. It also helped me focus more easily because I would zoom into and only focus on the very particular task at hand and know I would get that neurochemical reward after each “completion.” Otherwise the quantity of things needing doing at early stages would have simply been too overwhelming. I believe any writer could adopt a similar strategy to help them get through the massive project. Take that basic structure and tailor it to your own needs and project.

Like the reader said, a lot of non-fiction writing goes as such: Writer has an idea for a book; he sends proposals to publishers/agents; if interested the parties negotiate a contract often including an advance for the writer; the writer is given a deadline for completion and submits it when ready. Deadlines are both good and bad. On the one hand, you have a timetable keeping you on track and working. On the other, it could possibly limit how much you can include because at the end you just have to have it done and don’t have time to waste looking through things that may not end up being useful.

My book had an unorthodox beginning, so this wasn’t even a considered possibility way back then. Even after I took the possibility of publishing more seriously, I wanted to take my time and research at my leisure when I had time outside of the rest of life to do so. You can just write the book completely at your own pace and then try to get it published, which is what did. In the past that would have been risky because it would really suck to do all that work then never get it published. However, this is starting to change a bit thanks to online self publishing. Now anyone can publish their book without paying any costs up front and without worrying about rejection through this service. Well, except you want to get a review copy to make sure everything looks right which is like 7 bucks, and if you suck at art like me you will need to hire a designer to make the cover. I recommend upwork for stuff like this. [This trademarked website] also has pretty much the best royalty arrangements you can get anywhere including with traditional publishing so if you end up successful you will get paid way more. Best of all, if your content is especially controversial you don’t have to worry about pleasing anyone before making it available to the public.

The catch is that if you go this route you will have to do all the marketing and advertising yourself. That isn’t easy, and it requires a different set of skills than just writing. If you self-publish, be prepared to research and do a lot of work in this area. You will probably want to set aside an advertising budget.

If you go with a publisher, which is what I decided to do, they will work to promote your book for you. They obviously have lots of experience with this, or they wouldn’t be in business. Typically, they also already have a readership base they can make aware of your book. Even if you have a blog like me, I am quite sure that my readership base and Arktos’ only has so much overlap so it is helpful to have access to that community in addition to my own. If you are writing from the standpoint of reaction, then you already have a list of potential publishers who shouldn’t mind the content being controversial in that direction. Arktos, who I went through, Castallia house publishes Sci Fi mostly, but also has 2 non-fiction titles, and manticore press are three possibilities. There could be more, but I leave that to you to research.

At the end of the day, you have to make a decision to self publish or go with a publisher. Both have pros and cons. At the very least, though, it should be a relief to know that even if rejected by every publisher you can still make your work available.

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Smart and SeXy Kindle edition is now available for USD 6.95. Kindle Unlimited subscribers can download for free

Arktos has prepared and made available the kindle version of Smart and Sexy. Obviously this is available at a much cheaper price than the softcover version. However, the softcover version is also at a discounted price of USD 18.48 for the time being. I personally prefer having real paper to look at when I am reading, but it is hard to beat more than a 50% discount at USD 6.95. For those of you who wanted to take a look at Smart and SeXy, but thought it was too expensive, hopefully this option will be more amenable to you.

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Power, Sex, Suicide: Or why do genders exist in the first place?

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There has been a lot of crap happening the last few weeks, so I thought a not particularly political post might be a nice respite for some. Please bear with the large digressions in this post. It may not seem like it, but it is all related in a meandering sort of way. I promise. I will get to the point eventually and hopefully you will learn some interesting things along the way. Anyway, I wanted to expand on the evolutionary origins of two sexes (as opposed to none or more than 2). I did not cover it in Smart and Sexy because it wasn’t directly relevant enough to be included. The focus in the book was the intellectual differences between human genders, not why gender exists in the first place. It would have been too much of a digression to include that. I think it is an interesting question nonetheless and wanted to address it at some point. Especially since a growing group of lunatics keep wanting to expand the number of genders to the limit of infinity.

On to the first “non sequitur,” or so it deceptively seems. There was recently an askreddit thread which asked about atmospheric oxygen concentrations during the carboniferous period and reminded me of the topic of this post. Specifically, the oxygen concentration was an astounding 35% compared to today’s 21% and the person wanted to know why it was so high and why it dropped so much afterward. If we went back in time to that era, we would suffer from oxygen poisoning. I imagine that wildfires then must have been quite a hellish sight. Literally. This high oxygen concentration probably also explains why insects grew to be so large during this time, such as seagull sized dragon flies. Most insects depend upon passive diffusion to get oxygen to their cells and that is more effective at higher partial pressures of oxygen. Our lower concentration of oxygen today probably isn’t enough to enable such large insects, which is why they evolved to be smaller. Anyway, I had actually read some books which tried to answer this question and I relayed that info in the following comment:

Like most of the other ideas here this is a hypothesis. Life has made various evolutionary innovations over history and one idea is that woody bark/stems first evolved some time immediately proceeding the carboniferous. Woody stems are stronger and more resilient because there are protein cross links between cellulose strands. Cellulose being a long strand of linked sugars. Woody stems are very difficult to digest, which is why pretty much nothing eats it. When it first evolved, literally nothing ate it because it was so new and no organism had the tools to break it down. So, during the carboniferous trees and plants with woody stems proliferated because they had few or no natural predators, and probably also because they could grow taller than their competitors thanks to the strong stems and thus had better access to sunlight.  They did still die of old age however, and that woody material would just sit there without decaying. Eventually it would be buried and millions of years later we would dig it out of the ground as coal or oil. Most of the coal and oil deposits date from this period which is why it is called the carboniferous period.

Well, the process plants use to grow is that they take CO2 out of the atmosphere to build cellulose and other structural molecules and release oxygen. So what was happening in the carboniferous was that this was a very one way process. The carbon was being fixated and nothing was breaking down the large organic molecules to re-release it.

That all changed when fungi, think mushrooms and molds, eventually evolved the enzymatic equipment to break down woody stems. Some time at the end of the carboniferous presumably. With this second innovation, the woody part of plants didn’t just sit around waiting to be buried, it was broken down and the fixated CO2 was released back into the atmosphere. Obviously this added a new variable to the equation and the oxygen level in the atmosphere struck a new and lower balance.

I suggest “Oxygen: The molecule that made the world (Oxford Landmark Science)” and “Power, Sex, Suicide: Mitochondria and the Meaning of Life” by Nick Lane if you are really interested in this subject.

Some of the other comments did touch on this same idea but some people argued that the carbon dioxide concentration wasn’t high enough to account for all the oxygen. That honestly doesn’t make sense to me. The only process I know of which can oxygenate an atmosphere is photosynthesis, and photosynthesis absolutely requires carbon dioxide molecules to run to completion and release oxygen. One carbon atom is fixated for every one molecule of oxygen released (elemental oxygen is a diatomic molecule [except ozone which is triatomic oxygen but that doesn’t matter for this discussion]). Yes, CO2 was much lower in concentration than oxygen but that was because it was being used up. Venus and Mars both have much more carbon dioxide, for example, and presumably so would Earth if there were no photosynthesis.  Wildfires and volcanism were probably the main things getting CO2 back into the atmosphere which explains why it was never completely used up. In fact, carbon dioxide concentrations at the time were three times higher than pre-industrial levels, and double today’s level, but that was still only about 1-1.2% of the atmosphere. My guess is that Earth’s core was hotter, and that there was far more volcanism then than today. That would have made for a very high rate of carbon dioxide release which fueled the one way carbon fixation trip going on in the plant world. The point is, the idea that “there wasn’t enough carbon dioxide” is a red herring. oxygen release simply can’t happen without carbon dioxide, period, and the reason it was so low and not 96% of the atmosphere like on Mars is because of the stupid high rates of fixation.

As a side note, life seemed to get along just fine with atmospheric carbon dioxide levels double that of today during the carboniferous… Plants grew so abundantly in fact that this time period produced great deal of our oil reserves; perhaps even most of it. We also had monster sized insects. I don’t know why climate skeptics never mention this. It goes a long way in demonstrating a bit higher carbon dioxide concentration isn’t going to end the world.

At the end of my comment I mention two of my favorite lay-person science books. Both by Nick Lane, the first is Oxygen and the second is Power, Sex, Suicide. (You can consider the majority of this post to be an indirect summary of these books). The first one I read was the later, which also came out after Oxygen. Both books are great, but I have to note that there is a great deal of overlap between the two. For those of you familiar with mitochondria you can probably guess why. If not, the short answer is that mitochondria take oxygen and use it to to break down organic molecules into water and carbon dioxide. The energy released via this reaction is captured and used to fuel life itself. So, a book on the history of oxygen is by necessity going to overlap a lot with a book on mitochondria. My impression overall is that the material in Oxygen was reworked, improved, and added to new material to create Power, Sex, Suicide. Thus, if you read the later you will have most of the information you could have gotten in the former (though not all). If you had to pick only one to read, Power, Sex, Suicide is the best choice.

The title of the book was absolutely inspired. If you read the title your first thought is that it is about some game of thrones-esque political intrigue. Chimps throwing shit at each other is of course one of the most attention grabbing topics for humans available so anytime you see it on amazon, your gaze is instantly drawn there. The provocative title is what made me take a closer look. However, what makes it even better is that it is in no way deceitful. It is a book about mitochondria which are the power stations of the eukaryotic cell. All large multi-cellular life depends on this power generation. This is the most widely known fact about mitochondria and I will leave it to the reader to learn more about it.

Skipping sex for a second to briefly mention suicide, it turns out that mitochondria are important for signaling apoptosis, or programmed cell death. I.E., suicide. Two of the main reasons for this to happen is for fine tuning body structure and reducing the risk of cancer. In the first case, an example would be when hands grow in the embryo they are initially webbed then cells between the fingers intentionally die off so the fingers are separate. In the later, when a cell becomes damaged and malfunctioning (and thus more likely to eventually become cancerous) this can usually be detected and trigger the cell to commit suicide before developing into full-blown cancer. Obviously this doesn’t always work, but it definitely helps to cull damaged cells. Aging may be tied to this phenomenon because over the course of a lifetime the population of stem cells slowly depletes as they become damaged and are culled to prevent cancerous growths. Stem cells are the most likely to turn cancerous because they are the only cells which continue to rapidly divide, which means bad mutations are more likely to occur and regular or rapid cell division doesn’t need to be turned on via new mutations before the cell line becomes cancerous. Of course, having a lower population of stem cells reduces your body’s ability to keep all your tissues in a youthful state. Thus it is possible that aging, at least in part, is a result of evolved mechanisms for reducing the risk of cancer. Those suicidal mechanisms require mitochondria.

And now on to Sex. What does mitochondria have to do with Sex? Well, as it turns out, they have everything to do with sex. But to understand that, you first need to know the history of how mitochondria came to be. When life first came to exist on Earth, the planet did not have an atmosphere with much oxygen. There were plenty of reduced molecules floating around the oceans and being released via volcanic vents which could be oxidized for energy. (The term “oxidized” was originally coined when scientists thought only oxygen participated in this type of reaction, which was a long time ago. The definition has since been expanded to include reactions which don’t involve molecular oxygen but the name stuck. Path dependence. Obviously the first life wasn’t using molecular oxygen to derive energy when there wasn’t any molecular oxygen available.)

Eventually photosynthesis evolved in the ancestors of modern day cyanobacteria and chloroplasts. Light was a readily available source of energy which did not require any preexisting source of reduced molecules. Carbon dioxide at the time was probably at Venus or Mars percentages so that was absurdly abundant too. The cyanobacteria thus did extremely well, spread everywhere including places with no other source of energy, and proceeded to oxygenate the atmosphere at a massive scale. At first, however, preexisting reduced molecules present in the oceans would have quickly reacted with the released oxygen and thus the build up of the gas would have been delayed. Perhaps for millions of years. Evidence for this comes in the form of banded iron formations. Reduced iron is far more soluble in water than oxidized iron, so oxygen would be released, it would react with the iron, then the new molecule (rust basically) would sink to the bottom of the sea floor forming these bands.

Eventually, however, these reduced reactants would have ran out and oxygen would have started building up in the atmosphere. Believe it or not, oxygen is actually a very poisonous gas. And yes, that includes to you as well. We can live in it only because of evolved mechanisms that deal, incompletely, with its extreme reactivity. (This is not an endorsement for antioxidant products, personally I think that stuff is useless. Or worse than useless if it keeps cells functional long enough to avoid triggering apoptosis and thus allowing them to become cancerous). All of this poisonous oxygen in the atmosphere created a selection pressure for mechanisms that could mitigate the problem. In short, eventually this led to not only the ability to mitigate the presence of oxygen free radicals, but to actively harness oxygen as an electron acceptor in the production of usable energy. Some bacteria, including the ancestors of mitochondria, developed this ability. Though it isn’t entirely clear how it happened, one of these oxygen loving bacteria was engulfed by an archaeal cell (site with more detail). Probably with the intention of using it as food. Either that or the oxygen loving bacteria became parasitic on archaeal hosts. At some point this predatory or parasitic relationship goofed up and both cells started working symbiotically. The larger cell could provide shelter and sources of food, while the newly formed mitochondria could use oxygen to efficiently convert that food into energy and possibly transfer oxygen defense mechanisms to the host cell if it started out oxygen intolerant. This was the origin of all subsequent multicellular eukaryotic life, including you. A descendant of this lineage similarly engulfed a cyanobacteria and that become the universal ancestor of plants.

Some time later, the early eukaryotes developed sexual reproduction where genetic material is shared between two individual members of the species in order to reproduce as opposed to earlier binary fission. Reasons why are debated, but my preferred explanation is that sexual reproduction increases the probability of novel genetic combinations which may have increased evolutionary fitness especially with respect to, but not limited to, evading predators and parasites (including infections). Keep in mind that the origin of sexual reproduction is not the origin of the sexes. You don’t necessarily have to have two genders to sexually reproduce. (This is a general biological fact and should in no way be misconstrued as an endorsement of any sort of mental illness related to gender in humans. It doesn’t matter how worms do it, we are human and we only have two genders).

The advent of sexual reproduction, however, created a problem not dissimilar in type to the penis fencing worms in the previous link. That is, evolutionary self interest creating bad incentives for competition during reproduction. In the case of worms they are trying to reproduce without incurring the metabolic costs of growing eggs. Between mitochondria competition needs a bit more explanation, though. Mitochondria within eukaryotic cells have never completely lost their genome even today. Each eukaryotic cell thus has two methods of transmitting genetic information to descendants. One is through the mitochondria and one is through the nucleus. Even though mitochondria only increase in number via binary fission, random mutations can occur during that process thus allowing separate mitochondrial lines to evolve independently of one another. Since mitochondria have their own genome, reproduce, and are variable they are subject to natural selection. If in sexual reproduction two mitochondrial lines are placed together within the same cell, you create a situation of direct competition between both lineages for the domination of that cell and thus the opportunity to be passed on down the line. Competing mitochondria could and would evolve ways of eliminating rivals. Ways which would only have minimum concern for the overall well being of the host cell. What does it matter how the host cell does if that other mitochondria wipes you out?  Even at the cellular level, diversity + proximity = war. An evolutionary war between mitochondrial lineages going on within the cell is obviously not a desirable situation for the organism as a whole. Eliminating the potential for mitochondrial war would be a great advantage to any eukaryotic organism which managed to accomplish it. Basically, the nuclear genome would need to step in and tell everyone to play nice… Na, its much easier to build a big wall.

Which, 2500 or so words in, FINALLY gets us back to the title of this post. I do apologize, but I feel the explanation is incomplete without the requisite background information. Having two sexes is a direct response to this issue of battling mitochondrial lineages and is what gives us our most universal definition of two sexes. Having distinctive male and females genders is “the wall” so to speak keeping different mitochondrial lineages from directly competing with each other. Specifically, the female sex is that which donates mitochondria to offspring and the male is that which does not donate mitochondria to offspring. That’s it. This is the commonality, the only commonality, between all males and all females in all species which have distinct genders. It also explains why more than two genders is in no way necessary. Two individuals is enough to gain the benefits of sexual reproduction and two sexes is enough of a wall to prevent intracellular competition via natural selection in mitochondria.

As I have already pointed out, there are examples of sexually reproducing species which do not utilize two different genders. In the case of fungi, I am not sure how they deal with the issue of mitochondrial war (or if anyone else does) but I am sure they have some mechanism for it even if unknown. Maybe creating billions of spores renders it a moot issue because there is more than enough opportunity for both lineages. In the case of the penis fencing worms, you can see the problem of not distinguishing genders quite saliently. Two individuals attempt to forcefully inject (rape?) each other with sperm while not getting injected themselves. You have got to love the sadistic creativity of nature for creating a species in which each individual acts as both the rapist and the rape victim at the same time. You’ve got to rape before you get raped. This method of reproduction can and does cause injury to the rape “victim” which could lead to infection and other issues. Not exactly ideal from a fitness perspective.

And this is why sexually reproducing organisms have evolved a binary gender dynamic many, many times independently. Evolving a male and female sex is one of the best examples of convergent evolution because it has happened so many different times.  Most people are already familiar with sex determination in mammals which is determined via an XY system. Two X chromosomes gear the human form to passing on mitochondria (i.e., female) as well as other things, while an X and a Y chromosome gears the human form to not pass on mitochondria (i.e., male) again among other things. But the mammalian XY system isn’t the only way this mitochondrial division of labor can be accomplished. Fruit flies, for example, have an independently evolved and completely unrelated XY sex determination system. Hymenoptera insects (ants, bees, and wasps) have a haplodiploidy sex determination system in which the male only has one set of chromosomes (haploid) while the female has two sets of chromosomes (diploidy). A number of lizards and other reptiles use a temperature determination system. Some fish determine sex via social hierarchy. (Again this is not an endorsement of mental illness in humans, despite wikipedia believing it is.) Even plants can’t wait to give up hermaphrodism and divide into two sexes and that has happened independently a ton of different times. Last in my list, though I won’t claim it is exhaustive, is the ZW sex determination system present in some birds, turtles, crustaceans and so on. Mirroring the XY system, ZZ is male and ZW is female. Like with mammals and fruit flies, when these species are not closely related chances are these systems are also independently evolved. It has recently been called into question that the bird ZW is actually independent of the mammalian XY because of discoveries with the playtpus sex determination system. I tangentially discussed this in an April fools article I wrote on hybridization theory a while ago and I will let you read it to come up with your own conclusions. Keep in mind, a joke works better if you mix in some facts to make it more believable…

Regardless, you can see that using two and only two sexes has evolved again and again and again and again and again in completely unrelated species with incredible levels of divergence. Even in the sex changing fish they opted to have two sexes rather than just stay hermaphroditic. The fish are never both male and female at the same time. Having two and only two sexes, regardless of how that is accomplished, seems to be some sort of evolutionary equivalent of an energy minimum. Dealing with mitochondrial war doesn’t strictly require two sexes and other arrangements can work (in species that aren’t human), but clearly the two sex binary is one of the easiest and most effective ways for nuclear genomes to prevent intracellular war between mitochondrial lineages. Judging by the widespread level of convergence, cellular civil war must be a very common and extremely grave problem for biology to deal with. The existential urgency of preventing the internal war probably accounts for why an astoundingly large and diverse list of species have all converged on the two and only two sex binary. They keep falling back to that arrangement via remarkably different yet equally effective systems. And so that is why we have two sexes and not zero or a million. And it is why we will always have two and only two sexes.


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