#titan science

The Morphology of the Source and Its Evolution

Chapter 137

Based on its original form, the Source is composed of five main parts:

the head (x1), denoted by the yellow circle and distinguished as the more bulbous end

the spine (x1), denoted by the magenta line

the tail (x1), denoted by the red circle

the limbs (x9 on each side, with each end splitting into two), denoted by the blue circle

the spikes (x8 on each side), denoted by the green oval

While the Source retains this general form throughout the years, some of the parts show evidence of evolution over time:

Prior to speciation

The tail develops an antenna (much like the split ends that accompany the limbs).

The spikes lose their rigid structure (although this may be a matter of the Source exercising different methods of locomotion, such as swimming vs. terrestrial).

There are 13 spikes on each side of the spine.

Chapter 122

After speciation

The tail undergoes further splitting, forming tentacles.

The length of the spine increases, causing the number of limbs and spikes to also multiply (there are more than 9 and 13 on each side, respectively).

However, it’s important to note that these changes might have only been instigated due to the formation of the Dinosaur Titan.

Chapter 137

Chapter 137

Speciation and the Morphology of the Subjects of Ymir

This section examines how each of the five morphological features making up the Source combined with Ymir’s spine during speciation to give birth to SoY.

Chapter 137

The spikes attached themselves to Ymir’s spinal cord.

The length of the Source settled along Ymir’s spine.

The head and the tail fused themselves with each end of Ymir’s spine. Interestingly, the head is actually the part that bonded with Ymir’s sacrum (creating what I believe to be the compartment where titanizing spinal fluid is stored), while the tail settled in her upper cervical vertebrae (thereby providing the connection between the Source and the human brain). Essentially, the Source merged to parallel an upside-down human spine.

The limbs wrapped themselves around Ymir’s ribcage, reinforcing her ribs. 

Chapter 122

In this way, the Source and Ymir entered a symbiotic relationship, one of both parasitism and mutualism. Additionally, the Source altered Ymir’s intermediate anatomy such that all SoY are only morphologically distinct from other Homo sapiens through the construct of their spines.

Bonus: Speciation and the Neurology of the Subjects of Ymir

If we consider the head of the Source to be where its coordination centre resides, it can be argued that the body of a SoY houses two brains along both ends of their spine.

This is why, even if the human brain of a shifter sustains damage (e.g. Reiner) or the connection between the Source and the FT’s human brain is severed (e.g. Eren), the SoY is still able to heal.

In Reiner’s case, since the source brain in the hybrid spine within him was still functioning, it allowed for the transfer of his consciousness while his human brain regenerated. As for Eren, he was rescued from death because the brain of the Source residing within him commanded the tail to reattach itself to his human head (more on this later).

The Transmission of the Source via the Founding Titan

Now, since the Source merged with Ymir’s spine to create this fused spinal structure, it’s important to keep in mind that her spine and the Source are one in the same. Consequently, although Ymir passed on the morphological features of her hybrid spine to her daughters (and subsequent SoY) by means of hereditary genetics, they weren’t born with the original Source inside of them (because there is only one of it and it was bound to her spine). It’s not until they ate her that the Source migrated to one of their bodies, and that would be whoever inherited the FT (which I suspect is the first person to have consumed a part of her spine). 

In other words, the FT wielder is the only SoY whose spine houses the Source (+ the spine of Ymir, which is what’s been allowing her to live on). This is essentially what distinguishes the Coordinate from the rest of the Nine Titans.

Secondly, for the FT to be inherited, the Source needs to physically move from one host to another. This is accomplished via oral consumption. Once consumed, the Source is able to use its healing power/ability to grow in size (which it lends to SoY through the Power of the Titans) to grow back inside the new FT wielder and bind with their spine. Thus, much like other real-life parasites, being consumed is not fatal to the Source.

The Weaknesses of the Source and its Singular Cause of Death

While the Source can surpass death by cycling through a multitude of hosts, it can be inferred that it can only do so by (1) being physically transmitted, and (2) maintaining a physical connection with a live host. That is to say, these two requirements are the weaknesses of the Source and the key to its fatality.

To elaborate, the physical transmission requirement would mean that the Source (and therefore the FT) cannot actually be passed along to a newborn baby via PATHS. I believe that ability is only inherent to the other Nine Titans since their shifters do not house the Source within their bodies. Consequently, if the FT wielder were to die without having their spine consumed, that would spell the end of the Source.

This leads me to an explanation for the Source’s behaviour in chapters 122 and 137. Since the goal of the Source is to persevere in life, if its connection to its host is severed (and no transmission follows), it will always automatically revive the FT wielder using its healing ability, even if they’ve been beheaded. In other words, the FT cannot actually be killed by traditional means of severing the nape, because the Source will instinctually heal/revive its host if its weaknesses are exploited.

Chapter 137

Thus, in order to kill the Source and destroy the Power of the Titans once and for all, one must kill its host (the FT wielder) and prevent its failsafe mechanism (the revival of the shifter) from succeeding. 

The Transformation of the Source into the Dinosaur Titan 

Having established that the Source, Ymir’s spine, and the FT are one in the same, as the current FT wielder, Eren’s spine is also a part of this entity. This is why, when Eren’s spine leaps out of his body to reconnect with his head at the end of chapter 122, it looks more like the Source than it does a regular human spine. Essentially, activation of the failsafe mechanism causes the Source to revert back to its original form (this is also why, when Jean later blasts the Dinosaur Titan’s head off, the Source spews out of its spinal cord in its original form).

Chapter 122

Thus, the Dinosaur Titan that subsequently forms is a manifestation of the Source itself. This is also evident in the way that its upper half (denoted by the black circle) exhibits the morphology of humans while its lower half parallels the original form of the Source.

Chapter 130

To further illustrate, the following morphological features of the original Source correspond with the following parts of the Dinosaur Titan’s upper half (the human skeleton):

the tail = the skull (with the tentacles serving as the connection between Eren’s human head and the spinal cord of the Dinosaur Titan)

the spine = the spinal cord 

the limbs = the ribcage

the spikes = the vertebrae

Chapter 122

As for the Dinosaur Titan’s lower half, it fully parallels the original form of the Source but on a larger scale. It also excludes the tail as that part belongs to the upper half of the structure. 

Implications for the Ending

Putting all of this together, what’s important about the Dinosaur Titan being the Source itself is that, if the Alliance manages to destroy it before it can reconnect with Eren’s human head, then that should result in its death (as well as Eren/Ymir’s) and consequently, the end of the Power of the Titans. 

Rationale

These three scenarios had one common result: a SoY not possessing the FT was able to access the PATH—the Coordinate’s—without possessing the FT.

This isn’t far-stretched when you consider how a non-royal SoY is able to utilize the FT simply by touching a royal Titan. In the same way, I believe a SoY can be brought to the Coordinate PATH if they’re consumed by a Titan of royal blood/one who was titanized via the spinal fluid of a royal/one created by a royal. Essentially, due to the nature of PATHS, SoY can transcend the bounds of royal blood through physical contact with a fellow SoY who does possess those genetic requirements. 

This would explain how Armin and Zeke, who do not possess the FT, were able to “physically” access the Coordinate PATH, and why Ymir only arrived in it after her “death” (based on her surprised expression, she never saw PATHS prior to that moment).

To illustrate, here is a case by case breakdown of each scenario:

Chapter 114

A mindless Titan that was titanized by Zeke’s (a royal’s) spinal fluid and controlled by Zeke’s desire to fulfill his wish, placed Zeke in its stomach. In this way, Zeke was essentially “eaten”. Zeke was then transported to the PATHS dimension, where he met Ymir, despite not possessing the FT.

See NOTE under “Chapter 122”.

Chapter 122

Ymir’s case is special because she was the Founder and thus her successors didn’t inherit their powers by traditional means (that is, [a] transform into mindless Titan [b] eat shifter).

Instead, Ymir’s daughters (who possessed royal blood) ate her while in human form. She was then transported to the PATHS dimension despite not wielding the FT any longer.

Moreover, notice how her consciousness only fully transported to PATHS once her daughter ate her. She wakes up there to the scene of being consumed. Most importantly, Ymir was able to see everything from then on because, as Armin describes in 136, she was in the Coordinate PATH. In other words, she didn’t gain this ability until the moment she was consumed.

NOTE: In regards to how both Ymir and Zeke saw the PATHS dimension before getting consumed, I believe this was due to the combination of them making a wish after shedding their blood on those flowers (hence that specific transition sequence). As a result, their consciousness was transported there prior to the consumption step, but they didn’t gain complete awareness/end up in the Coordinate PATH “physically” until it (the physical contact requirement) was completed.

Chapter 136

A puppet Titan that was created by Ymir herself (a royal) swallowed Armin whole. Armin was then transported to the PATHS dimension despite not possessing the FT (I believe this is why the Pig Titan went after Armin in the first place). 

Notice how Armin also only saw Ymir after making physical contact with the Pig Titan.

Chapter 135 

Chapter 136

What’s interesting is that being in the Coordinate PATH (despite not possessing the FT) allows you to be omnipotent; you can see everything that’s happening around you via other SoY. This is why Armin is able to keep track of what everyone is doing. His consciousness is in the PATH that connects all SoY, and as we know, they all cross at the Coordinate.

Summary

Typically, only the FT wielder can access the PATHS dimension when they’re using the FT powers, as it is the metaphysical manifestation of the Coordinate. However, other SoY (regardless of their blood type) can end up there if they are consumed (without being killed) by:

[a] a royal (in Titan form or otherwise), as in Ymir’s case,