Could Yeerks Really Evolve?

[Myitt]

Haha, thanks donut  Jessi is Teach, sorry.

Actually I sort of imagined Yeerks were haploid, sort of like fungus or gametes (sperm or egg cells)--their cells each had one half of a set of chromosomes.  When the three parents joined, the cells would all start to combine, and gene pairs would hook up and form diploid or triploid masses.  These masses would combine their genes, undergo meiosis (not mitosis), then split off into new haploid grubs.  If a diploid (or perhaps triploid) mass accidentally split off from the tripartite parent, then twin grubs would grow from the diploid mass (or perhaps rarely, triplets?  Or is there simply not enough cell mass for triplets to survive?)...

Just a theory, of course, but it seemed to make sense to me while I was daydreaming in genetics class XD

[Alex Oiknine]

Well, just to clarify, I would point out that they are not actually photosynthetic oranisms; that is to say they do not actually using energy from light to produce organic compounds for their bodies. Though the Anis frequently refer to the process with quips and phrases like "soaking up rays" it is explicitly stated that they are actually absorbing nutrients.

Not to intrude into the rest of the discussion, which is really interesting, however, it is stated that Yeerks need Kandrona rays, from their home sun or something like that. It's also important to note that one does not need to be a photosynthetic organism to have requirements such as this.

Our own body makes Vitamin D from our own sun's rays. We can get Vitamin D from fish or other organisms instead if that is unavailable, but I mean, our body is made to do that work all by itself. We're certainly not creatures that live off of photosynthesis. Since in The Warning we're aware that Yeerks can live in their host 100% of the time with the process of having their host eat Yeerks, we know they don't actually need to be out to acquire nutrients (further theoretically substantiated by The Underground where the oatmeal takes away their need for Kandrona Rays. The only thing consistent in the books is that they need Kandrona rays, and for some reason Kandrona rays only get synthesized properly into... whatever they need... by other Yeerks. So if they need Kandrona rays, they are either going to get out and do it themselves or get their host body to consume other Yeerks to get whatever it is they've needed the Kandrona rays for.)

I always assumed Kandrona rays provided some necessary function nutrient-wise for the Yeerks that they couldn't duplicate, synthesize, or get from other animals on their home planet (like we can with Vitamin D, for instance, by eating fish, or add Vitamin D to our milk), maybe something critical to them but not most other species around since they had a vastly different way of living than most of the organisms on their planet.

Maybe I already missed this part of the conversation, but just adding my 2¢ - I don't think needing Kandrona rays means they really needed nutrients or makes them photosynthetic anymore than our body needs our own sun's rays to turn some things we have in our body into things like vitamin D. It doesn't have to be an either/or matter here.

[Myitt]

Good points, Alex.  That's totally plausible, but the way I saw it was that the Yeerks used the inorganic nutrients in the pool plus Kandrona wave/particles to generate food stores (protein) in their cells, much like plants or algae.  My rationale for the Yeerks remaining in their hosts from oatmeal addiction was that the oatmeal somehow set the Yeerks' Kandrona receptors into a sort of feedback loop, providing whatever ion it needed to keep a constant food store without the need for energy from their home sun.  With Esplin the Lesser and his cannibalism, perhaps consuming processed Yeerks that had stored Kandrona-built protein would provide that same energy for his own body, in its most basic form, transferred through the blood-brain barrier of his host. 

Again it's all just conjecture, so either way it's interesting to discuss the possibilities, but you're right--Kandrona is something they definitely need to survive, whether they're photosynthetic or chemosynthetic autotrophs (like some bacteria and protists) or not. 

[Alex Oiknine]

With Esplin the Lesser and his cannibalism, perhaps consuming processed Yeerks that had stored Kandrona-built protein would provide that same energy for his own body, in its most basic form, transferred through the blood-brain barrier of his host. 

Well no, see, that's my point: They make it clear he can absorb whatever is needed through his host (blood brain barrier or otherwise). Additionally, they don't need to leave their hosts (if they've eaten oatmeal) for any known nutrient other than the Kandrona rays. To me that seems to indicate that, for whatever reason, this provides something, the only thing, that they need to leave their hosts for. Everything else it seems they can absorb through their host on a normal basis.

I'm not saying they don't absorb nutrients, only that it seems the Kandrona rays are the only consistent thing they need to leave a host body for - and it has certain ways around those rules.

Why they can't synthesize whatever it is Kandrona rays do for them, I don't know, I'm just saying that seems to be the only thing repeatedly substantiated in the books, so there can be a variety of explanations, none either here or there. I wasn't writing about what a person did or didn't see it as, simply pointing out that really the only thing we have that is rock-solid on Yeerk survival is the need for Kandrona rays. Explanations beyond that are totally up in the air for imagination, simple or as complicated as we want it to be.

[Myitt]

And I totally agree, Kandrona is the one thing they absolutely need, regardless of conjecture on why or how they process it.  I'm just giving my point of view on why I think they might have been autotrophs, with, like you say, a few ways around the rules of needing the Kandrona that fuels their (in my opinion) autotrophic cell system.

[Kotetsu1442]

We see at least two examples of lifeforms that may not be entirely carbon based.

Yeah, you actually bring up some good points that I failed to consider that prove that my 'possibility A', that within the Ani-verse all life forms are carbon-based, impossible. Not only is 'possibility B' (that carbon-based life is the most likely type of life and all things being equal will form more often than not) strongly suggested in our observing that the majority of lifeforms are encountered are carbon based, but very strongly supported in Tobias' narration in #23, The Pretender:

According to Ax, DNA is a very common thing in the galaxy. The same double-helix of DNA forms the blueprint for all life on Earth and almost all life-forms everywhere.

The only reason I included the 'possibility c' is that Andalite knowledge of life, though more advanced than us is still limited and though our galaxy, as far as is known by them, contains mostly examples of carbon-based life, it is possible given an infinite or sufficiently large  universe that the limited example happens to be a statistical anomaly of an unusual percentage of carbon-based life-forms in local proximity; so 'coincidence' is just as possible.

You certainly are not 'WAY off' on any of your thoughts, the only thing I would see as worth disputing is the idea that having what you refer to as a net of neurons throughout their body means that Yeerks have no central nervous system; rather I would say that the facinating thing about Yeerks is that they are almost nothing but a central nervous system, or as Myitt put it earlier:

maybe Yeerks are just big squishy brains without much else to impede direct contact between their neurons and the host's neurons, and this intellectual development helped aid their evolutionary development of infestation?

Furthermore, one thing that your thoughts, Terenia, brings up is another interesting aspect of evolution, because when evolution brings a specie to intelligent to the point of sapience (the details of how being greatly unknown when we only have ourselves as an example) then almost certainly psychology plays a role that is arguably just as important as physiology. When the Yeerks complain of Gedds being clumsy it makes sense that they are less preferable to other species as hosts, but the comments you bring up from #14 about preferring intelligent hosts causes one to wonder if this preference is merely a current social preference or is the result of evolution too. If the Yeerks are no more agressive than Humans in basic nature, then why would they have pursued the conquest of all intelligent creatures they could find when in the process of learning from Seerow they could have just as easily begun seeking hosts that are physically suitably capable that lack intelligence (Esplin's description of the 5-class classification of species based on suitability for infestation makes no mention of intelligence as being relevant), so it is worth wondering whether there is some evolutionary trait based on something in the Yeerk evolutionary history that makes infesting non-intelligent hosts so distasteful as to be inconsiderable.

(I would hope there is some very strong basis for this 'preference' because the premise that guided Cassie's actions, that Yeerks were at heart opposed to their actions of conquest and only justified it because it was necessary for them to freely experience life, was maintained by her throughout the series and we were assured that this helped bring an end to the war. Without a strong justification for this 'premise' that becomes a large plot-hole that is central to the entire premise and ongoing story. Furthermore, from the Sharks we see in #15, The Escape the Yeerks have rather impressive bioengineering technology (though not necessarily as great as the Arn, though most of it may have been stolen from them) so modifying suitable hosts is just as plausible a 'way out' when it has been asserted that the only reason the Yeerks continue is because they have none.

So yes, some very interesting thoughts, thanks for those reminders Terenia. What does everyone think about the Yeerks psychology, evolutionarily speaking?

[Terenia]

I mentioned this in chat the other day and I'm not sure how plausible it is, but here's my thoughts on the Yeerk tendency to infest sentient beings:

In their earliest evolutionary form, Yeerks likely inhabited other creatures on their planet that were 'aquatic' and eventually moved up the ladder to the semi-sentient Gedds. Now, I do not know how strong the instincts are of creatures on the Yeerk home planet, but based on the bits we do see the planet seems relatively sparse in lifeforms and those that do exist thusly do not necessarily need superbly strong instincts (compared to the incredibly complex abundance of life on Earth).

Now, once Yeerks tended towards infesting primarily Gedds a long period of time may have passed during which the Yeerks only infested Gedds. Over time they would reproduce with the tendency towards Yeerks best suited towards such a host - a semi-sentient host. Over time perhaps it became not impossible, but uncomfortable and unrealistic for Yeerks to infest non-sentient beings.

One of the constant problems Yeerks face is the maintaining of control. Yeerks, in essence, have two things to control within a sentient host: instincts and intelligence. On the flip side, with a non-sentient host they only have instincts to forcibly control. I think that, perhaps, with sentient hosts there is a tendency for base instincts to be milder. For example, we as humans do not experience the extreme predator/prey drive of a hawk/mouse. Similarly, though Andalites were once prey they do not spend all of their time running in fear from every shadow. Something within the Yeerks biology may make it easier for them to control sentient beings because the intelligence has already squashed (for lack of a better term) the strongest instincts. Perhaps the Yeerk body was simply not effectively equipped to handle a bundle of instincts.

An interesting note is that in #15, during the shark incident, they expand the shark's cranial capacity, thusly allowing enough space for a Yeerk to enter. However, they theoretically could have done so without altering the shark's intelligence, yet they do in fact increase the basic brain power of the shark. I can only imagine that by creating the possibility of sentience it helped the Yeerk adapt to the environment and override the basic instincts of the animal.

The only other incidence of a Yeerk infesting a non-sentient animal is seen in #14 with the horses. While horses are far from intelligent, Applegate's portrayal of them in the series shows no overwhelming instincts so long as they are not spooked.

In a nutshell: The Yeerk body has actually evolved to prefer sentience over non-sentience. It is better equipped to take and maintain control over beings capable of intelligent thought, rather than those who run strictly off of instinct, who may be able to break through the Yeerk's control unpredictably.

[Myitt]

I also think brain size is a factor, and with intelligence often comes greater brain size relative to body size, and greater brain complexity.  Which makes me wonder--how big are Yeerks, really?  I know this has been discussed before and in #6 the Yeerk Temrash is described as "not six inches long"...so a little under six inches in length, but really, how much area could a six-inch slug cover when pressed and flattened out?  According to a few science websites, like this one, the human brain when flattened out would be about the size of an average pillowcase:

http://faculty.washington.edu/chudler/compare2.html

So...would a six inch slug, when flattened out to a paper-thin layer, be more or less than that?  I'd say probably more...

As for Yeerk psychology, I think their society involves a whole lot of brainwashing and propaganda, which is fairly obvious throughout the series.  Those who are able to dismiss that dogma that's been forced into their minds since they were young might be able to reconcile things like feeling bad about taking unwilling hosts, but overall it seems the Empire has created a very messed up psychological base model for its citizens. 

On the flip side, I wonder if a Yeerk would make a good psychologist?

[Kotetsu1442]

Interesting thoughts, that line of thinking makes a lot of sense, and actually reminds me a lot of the Anis working to control a new morph and even control the more powerful instincts of one they are experienced with. In many respects it is the same struggle, though the methods of controlling the body of the morphs is different, they do physically create the animal brain as part of the animal body and it is referred to as having its own 'mind' in so much as an animal has a mind; often this is nothing more than a 'hard wired' processing of response to inputs but it can involve interpreting of inputs with enough complexity to be considered conscious thought.

In any case, the Anis working to control the morphed brain's instincts is at least to some degree comparable to a Yeerk's controlling a host brain even though the methods of linking the brains is completely different (furthermore, the Anis control an animal brain with a mind, but that brain/mind has no past experiences, it is just a method of observation/thought processing). It would have been interesting to see a Yeerk's perspectives on the experience of morphing, perhaps by spending time in Esplin's perspective trying out a couple of morphs in The Andalite Chronicles as we later (earlier chronologically, later publishing) got to see from his perspective in The Hork-Bajir Chronicles. Late in the series the Yeerks may have been found to be particularly good morphers, not in the shape-shifting as an estreen is, but in controlling the morph quicker and more completely because it is so closely related to their normal life-style and basic evolutionary training to learn to control another mind/brain.

[Terenia]

While we're on the topic of the Yeerk brain, I have to bring up this question as well: how intelligent/adaptable are the Yeerk brains? Based on what we see in the series they seem to be incredibly adaptable, almost unrealistically so.

When the Yeerks are first discovered they are a sentient but otherwise largely helpless and experience-less species. They had control of Gedds, tools that were along the lines of early civilization (wielding clubs and whatnot) and, according to HBC, had absolutely no knowledge that the stars even existed, let alone life on another planet.

Within only a few years (if that) of the Andalites occupying the Yeerk homeworld the Yeerks are capable of not only using, but understanding energy beam weapons and of stealing and effectively flying spacecraft (as we see in Alloran's holographic recording of the Yeerk escape). We know that they do steal technologies, but they have the mental capacity to not only understand how to use what they steal, but to innovate and invent new technologies based on the old.

So essentially the Gedds went from a pre-historic type of land based culture to a space age culture, practically overnight. Now I'm sure they did have a decent amount of intelligence gathered from the years spent in their pools, studying wave currents and whatnot, but how much practical knowledge did they have of certain aspects of science? Not much, especially in regards to technology.

So how did the Yeerk brain not only accept and use the new technologies, but so quickly become able to fully understand and innovate upon already existing devices? I imagine it would be akin to visiting Mesopotamia and giving the early inhabitants a hypersonic jet to play around with.

[Myitt]

Haha, that is an interesting (and pretty accurate) analogy, Jessi.  I've thought about that quite a bit too, and I guess the only evidence we have beyond the Yeerks' later capacity for developing new technology from the old is that "Seerow says they're really smart". 

Well, it's like you say, they're almost unrealistically so--unless we assume that they had built their knowledge base up to advanced levels in math and physics, but had no way to apply these rules other than for predicting pool currents or, I dunno, the timing of their day and night. 

If they hadn't even seen the stars, it also makes me seriously doubt that they even knew Kandrona was a star itself.  So when the Andalites came along, they not only saw bodies and technology that would help them finally advance beyond their otherwise tribal society level, but they also naturally saw a way out of the confines of their homeworld.

If you're entire body is practically made up of your brain, and your capacity for learning is just wildly adaptable, plus the Yeerks' abilities of storing and adapting host memory...I'd say their brains are like our own, but with far more of the usable, conscious parts unlocked.  A race of intelligent savants, where even the people who don't have a good scientific mind ("that kind of mind" according to Esplin 9466 in HBC) are still able to devote their attention to completely learning about something else (Andalite culture, for example). 

That doesn't mean that there weren't Yeerks who made poor decisions or were, by their standards, not too smart...but they certainly seemed to have a mental capacity well beyond our own.

[Kotetsu1442]

I disagree with you two on the point of it being 'unrealistically so'. Assuming that they are sapient but have a primitive culture then they aren't different than humans who spent thousands of years being just as intelligent as we are today but only made innovative changes over periods of lifetimes rather than months or years because they were caught up in the day-to-day struggles of survival and didn't have time to put that intelligence into progressive works. But then, under Seerow's tutelage over several years, young Yeerks would have no more difficulty becoming 'modern' and 'advanced' by our standards just by growing up with teachings of advanced knowledge. With that and assuming there was plenty of instructive material stored in the spacecrafts that were hijacked explicitly designed for education (the databases seemed to have a large store of general Andalite knowledge as well as very detailed scientific and technological information) then those born on ship in the 1960s (Earth-time) and being adults in 'present day' late 1990s would turn out much as we see them completely adjusted to the technology around them.

Their capacity for absorbing information may be beyond our own, but their creativity and adaptivity doesn't seem to be necessarily greater. The same would be the case if one of us took enough modern technology and stores of knowledge with us and began instructing young people in an ancient human cave-dwelling clan.

[Myitt]

I disagree with you two on the point of it being 'unrealistically so'.

Well, it's like you say, they're almost unrealistically so--unless we assume that they had built their knowledge base up to advanced levels in math and physics, but had no way to apply these rules other than for predicting pool currents or, I dunno, the timing of their day and night. 

Almost unrealistic.  Your points about their adjustment to advanced technology was the point I was trying to make about their huge capacity to learn.

[donut]

I'm not sure that they didn't have a very long time under seerow to gain working knowledge of the technology.  When they attacked the andalites they already had pool ships set up.  It takes a long time to design and then build a ship, so they may have had a significant time to learn.  Even if the ships were rigged ad hoc, it still would imply a long period of time just to understand and replicate the kandrona, and build computers that could be used by the yeerks.

Once they had the ships they weren't working from scratch, they had a huge database of information to work with.

It still took several years before they had developed the means to design their own versions of the ships and handheld weapons, which falls in the general time frame for reverse engineering technology.  Now the means to actually produce them I'm not sure about since they would have to build the industrial infrastructure first.

Also they didn't truly develop anything uniquely their own that we know of, except for the antimorphing ray which may or may not have worked.  So all of their technology may have been reverse engineered.

The thing that got me about it though was how effectively they fought the war with the andalites,  they had the andalites at a stalemate without much experience at fighting, whereas the andalites had who knows how many years experience fighting.

Now  as to the yeerks preference for intelligent species, I've got a few ideas.  First we need to consider what the yeerks need in a host.  Assuming they're infestable, a species needs 3 things to be suitable as a host, good senses, an ability to move, and an ability to manipulate objects, such as hands or tentacles.  Now most species on earth that have a decent ability to manipulate objects are very intelligent, apes, octopuses (octopi?) for instance.  There also needs to be a lot of them available, this would also imply an intelligent species since they would have the ability to survive beyond the typical outproduce-the-dangers approach and take ways to reduce or eliminate the dangers.  They also need to be fairly well concentrated, they had mentioned one species that could be infested but had spread out so much that they weren't worth taking.
I don't think the yeerks have much more ability to fight the instincts of the host than the host does, the series often mentions times when the yeerks couldn't control their facial expressions ( I believe Jake's yeerk was made by a microexpression), which are instinctive, well some are, or the ANS responses of the body.  I also wouldn't discount how strong instincts are in intelligent species, I don't think they aren't just as strong, I just think they don't come up as much.  People who have been put in survival situations often had strong urges to do things that have saved their lives without ever knowing why.

I always wondered how much the yeerk was affected by the mind of the host it had taken.  Take Taylor for instance, the yeerk that took taylor was supposed to take a much more important human later, but decided she (for simplicity I refer to yeerk's by their hosts gender) liked the feeling of being beautiful so much she stayed in her (or something like that) which was one of the things the host felt.  It's hard to say because we don't get much about the yeerk before she infested her.  I don't know much about the yeerk peace movement but I'm pretty sure it started with yeerks who had human controllers.  There's also V3, who although was always calculating and ruthless, didn't seem to develop his deep bloodlust or extreme arrogance until after he took an andalite, who was extremely arrogant and did have a deep bloodlust.  Since the yeerks had only taken a few species en masse it's possible that the yeerks themselves didn't know about this.  The Hork Bajir were described as being so simple minded that they didn't really understand what had happened when the yeerk had taken the HB, the taxxons were single minded from their hunger, and the gedds were implied to be less intelligent than the HB.  The only species that did have complex psychologies before the yeerks started taking humans were so few that there probably wasn't any notice of it.

[Terenia]

I always wondered how much the yeerk was affected by the mind of the host it had taken.

This, I think, is an interesting speculation.

From our reading we see Yeerks with several kinds of hosts (listed in order of preference: Gedd, Taxxon, Hork-Bajir, Human and Andalite

It's interesting to note that humans and Andalites, on the scale of sentience, seem to be quite a bit above the Gedd, Taxxons and Hork-Bajir. I'm pointing this out because our only examples of 'host sympathy' come from the host bodies that belong to a more individualized race.

In the case of human we have a few examples: Edriss, Tyler, the Yeerk from #8 (forgot his name), Karen/Aftran. In each of these cases you have Yeerks 'go human', or in some way give in to either human instinct, emotion or personality. Tyler is the most extreme example, blurring the line between Yeerk and human so completely that they are almost the same person.

In the case of the Andalite, we have Esplin. I'd like to argue that Esplin too fell victim to 'host sympathy' in a very odd way. In HBC and TAC we see a very different Esplin 9-4-6-6 than in the canonical series and Visser. We see an intelligent, astute Yeerk who knows how to get ahead in the war. He is intelligent about his rise to power, and about obtaining his Andalite host. However, in the canonical series, after many years with Alloran, he seems to become a warmonger. He is more arrogant and more cut-throat, characteristics that Alloran possessed. Though Esplin would never openly sympathize with his host, I think he took on some of Alloran's personality traits subconsciously.

This trend does not seem to be noticeable in the barely sentient Gedds, hunger-driven Taxxons or genetically-created Hork-Bajir.