How Mitochondria used to be Parasites that Created Gender

Forward: I’ve been too busy this past week to write an article but didn’t want to be on hiatus for so long. I found this article which I wrote four or five months ago but didn’t post because the humor turned out a lot darker than what I would normally do. I dunno, mitochondria are just really based and spicy, I guess. Keep that in mind.

Table of contents:

• Intracellular Parasites
• Mitochondria’s Parasitic Past
• Gender and Mitochondria
• Intragenomic Conflict
• Wolbachia
• Comments

Mitochondria are the Powerhouse of the Cell

We all know that the Mitochondria is the powerhouse of the cell. Many of you may also know that the Mitochondria used to be their own organism and still has their own DNA.

Often, this is explained as a single cellular archaea eating a bacteria but for some reason didn’t digest it. The bacteria just sat inside the archaea, completely unharmed, until it eventually evolved symbiosis with its host. By this point, they’ve become so intertwined that it doesn’t even make sense to call the two separate creatures anymore. While the idea that mitochondria are just extremely dedicated vore enthusiasts is amusing, it’s almost certainly not what actually happened.

Intracellular Parasites

Let me introduce you to intracellular parasites. An intracellular parasite is a single cellular organism, usually a bacteria, which hides inside of another cell to parasitize it. 

How exactly the parasite gets inside a cell, known as intracellular invasion, varies wildly between species. All of the possible methods are pretty technical and difficult to explain without diagrams, so I am not going to bother. If you are curious, check out the further reading I have linked here (Colonne, 2016). After you read my article of course. All you need to know is that it results in the parasite floating around inside the host cell. Oftentimes inside of a bubble made of the host’s membrane called a vacuole. 

You are probably already familiar with a common intracellular parasite. If you enjoy your chicken medium rare, you may be intimately familiar with it. Salmonella is an intracellular parasite that likes to hide from the immune system by being inside your cells. Chlamydia is also an intracellular parasite.

Mitochondria’s Parasitic Past

But how do I know that Mitochondria used to be an intracellular parasite? Well, I don’t. This happened like two billion years ago. I can’t just hop into a time machine with a microscope and ask my 2x10e¹⁰th great-grandparents if they’re on friendly terms or not. What if I step on them? Can you imagine the kind of butterfly effects and grandfather paradoxes that would cause? This is precisely why the TIMETRAVELANATOR™ is to be used exclusively for banishing my archnemeses into the distant future where my evil is law. Also for save scumming in Jump King, but that’s it.

However, there is a lot of pretty good evidence so we can be pretty sure. For one, you could clearly imagine how an intracellular parasite could evolve into an endosymbiont like a mitochondria. It’s fairly common for parasites to evolve into symbiotes. Cooperation for mutual benefit is generally better than not because of the prisoner’s dilemma and game theory. However, it usually isn’t quick to evolve because evolution is short sighted. 

Also, we have used science and genetics to figure out which of the currently existing germs are most closely related to our mitochondria. Turns out that it’s rickettsia, which is the intracellular parasite that causes typhus fever and a number of other diseases. All I’m saying is that the apple doesn’t fall far from the tree.

Also, saying that some archaea just ate a bacteria without digesting it, and then it evolved into mitochondria doesn’t really make sense if you think about it. Mitochondria are pretty heavily specialized to be able to produce enough energy for the whole cell. No preexisting bacteria would be capable of that. There would have needed to be quite a bit of evolution inside the cell to really become useful. Why did they keep this arrangement for the hundreds or even thousands of generations needed to evolve into mitochondria? How exactly is a freeloader your great-grandfather ate and now lives inside you basically rent-free not a parasite?

Gender and Mitochondria

As a bonus, did you know that mitochondria are also the reason why gender exists? That’s right, the reason you feel the need to reaffirm your fragile masculinity by joining a frat and smashing beer cans on your forehead is Mitochondria’s fault. Or whatever the sorority equivalent of that is. You can tell your parents that when they ask why you’re failing all your classes.

When a genderless eukaryotic cell and another genderless eukaryotic cell love each other very much they fuse into a single cell known as a zygote. The zygote then undergoes meiosis and splits into multiple smaller daughter cells which have the DNA of both parents. No gender required. I also feel obligated to say that zygote also sounds like a pokemon name.

But remember that Mitochondria were, and in many ways still are, their own organisms. They have their own DNA meaning they evolve separately from us. Normally, adaptations which are good for the Mitochondria are also good for us. But, because evolution is shortsighted, sometimes the Mitochondria does something which really isn’t good for us because it’s good for them in the short term.

Intragenomic Conflict

The problem is the Mitochondria in these cells would benefit if all the daughter cells only had mitochondria descended from them and don’t have any mitochondria from the other parent cell. This is because, much like Germans from before color was invented, Mitochondria are both very productive and very racist. They’re mainly afraid of being replaced by races which are more fecund yet are also genetically inferior somehow? I dunno, I’m not *that* kind of mad scientist. 

My point is that it’s genetically advantageous for mitochondria to get rid of competition. So when a mitochondrion evolves to attack and kill foreign mitochondria in the zygote that trait spreads. Soon, most cells will have racist mitochondria.

But if two cells fuse and both have racist mitochondria they’ll just annihilate each other leaving the daughter cells with few to no mitochondria. This is known as an intragenomic conflict. If I can continue the Nazi metaphor, which I certainly shouldn’t, this is like how their racism got half the Fatherland leveled by American bombers and the other half raped by Soviets then given to Poland. Don’t do racism, kids.

It turns out that the best solution for mitochondria racism is to arbitrarily genocide half of them so that different mitochondria can be segregated and never have to interact. See, the joke is that this is very obviously not the solution for real-world racism, in fact it’s the exact opposite, so saying that is so absurd that it’s funny! Haha, I hate myself. 

Anyways, evolution just made half of the host cells start killing all of their own mitochondria right before doing the horizontal fusion dance. The ones which do that are by definition male. The ones who get to keep their mitochondria are by definition female. The male gamete, or sperm, are also usually smaller than the female egg. That’s actually all that gender is. Everything else we associate with gender just gets tacked on afterward.

I find it interesting that gender originally evolved as a weird roundabout way of solving a shortcoming of evolution. You could imagine an alien world where gender never evolved. Maybe they managed to evolve a powerhouse organelle without symbiosis. Maybe their equivalents of mitochondria were reduced to the point they lost all their DNA and don’t evolve independently. Aliens from that world would probably be very surprised to learn about gender. And maybe we would be surprised by something equally weird that only they evolved.

Wolbachia

Some interesting side effects have come out of intragenomic conflict and gender. Wolbachia is another example of an extremely common intracellular parasite that mostly only infects insects. In fact, most insects that exist are infected by a species of Wolbachia bacteria.

Wolbachia can also infect the host bug’s children by hiding inside the egg cells. However, if Wolbachia is in a sperm cell it will get genocided along with the mitochondria. Sperm, also like Germans, are very efficient and leave no stone left unturned. Therefore, Wolbachia would prefer to be in a female bug rather than a male bug because they can only spread to the next generation through females. 

But sometimes, like at an orgy, a Wolbachia finds itself inside a guy and just has to make the most of it. Unlike the relatively friendly mitochondria, the Wolbachia parasite is willing to take drastic measures to fix this problem.

Some species of Wolbachia have evolved to end toxic masculinity by straight-up castrating their male hosts. Others pinkpill their hosts and turn them into fully functional girls able to lay eggs. 

This is pretty bad for the insects as they need to have at least some guys left to boink all the new transbugs. If every dude is tf’ed into a dudette, the species will go extinct. Or, if they’re lucky, manage to reproduce asexually. But that is only kicking the can down the road. Asexual reproduction just makes clones. Asexual species evolve far, far slower and will eventually be wiped out by something else they can’t adapt to. 

By the way, if your bro gets turned into a hoe, would dating her be in violation of the Bro Code? Is that bros before hoes? If you have the option of dating a bro hoe or a hoe hoe, does the Bro Code mandate that you go out with your bro first or not at all? Would you still need to say no homo? Please help me figure this out in the comments, the Brocode ISO is very unclear on the issue.

Further Reading:

Colonne, Punsiri & Winchell, Caylin & Voth, Daniel. (2016). Hijacking Host Cell Highways: Manipulation of the Host Actin Cytoskeleton by Obligate Intracellular Bacterial Pathogens. Frontiers in Cellular and Infection Microbiology. 6. 10.3389/fcimb.2016.00107.