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[^1][^2][^3][^13][^4][^5][^11][^6][^12][^9][^10][^7][^8]
# Introduction

This summer, I attempted to learn how to pitch a ball in order to understand how humans evolved.
<br><br>What?

Yes, somehow, [this](https://i.gifer.com/CNgs.gif) is connected to [this](https://cdn.britannica.com/60/94660-050-DC91376F/divergence-humans-apes-ancestor.jpg).

The two may seem unrelated, and any attempt to form a causation relationship between the two may seem farfetched; if we step back to think about the richness, complexity, and vast scale of human history and uniqueness, it may be difficult to attribute it to something as seemingly trivial as an ability to throw. And I understand, as this was also my initial reaction.

But lethal full-body projectile throwing is a uniquely human ability. And I hope that as you come with me on a journey through an exploration of my own throwing mechanics, you will be able to see what we are talking about: the ability of humans to throw with such bio-mechanical prowess opened up a whole different kind of animal society that was not possible before. Additionally, our own bodies are themselves proof of this theory because we all have inherited these biomechanics from our ancestors.

But let's start with this:

# 1) PITCHERS ARE DEADLY.

I never really got into baseball. Besides the fact that I *have* been paying much more attention to it ever since a player named Shohei Ohtani emerged onto the scene, I wouldn't call myself a fan.

However, this particular video has fascinated (and haunted) me since I saw it on Youtube as a middle schooler. It's a video of pitcher Randy Johnson hitting a bird with a fastball so hard that it bursts into feathers and dies instantaneously.
:::warning
Warning: Graphic.
:::
<iframe width="560" height="315" src="https://www.youtube.com/embed/Ih_ovjbwQGk" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>

He's not at all the only pitcher capable of this. MLB pitches **consistently average speeds of over 90 mph.**

How are they able to generate such force and velocity so consistently? Well, in addition to having the muscular capacity to do so, MLB pitchers have perfected their pitching forms to allow for direct, efficient transfer of energy throughout their entire bodies. The energy that goes into a baseball pitch actually starts from lower body movements as a pitcher swivels their hip. The energy generated in this movement is channeled efficiently and quickly into the upper body, which further redirects it into the ball through an arm movement. The path of movements that that this energy follows is called a **kinetic chain**.

You can clearly see this surgically precise coordination of movements in these videos of Shohei Ohtani's pitching form:
<iframe width="560" height="315" src="https://www.youtube.com/embed/3GTkhSDBzYo" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>

<iframe width="560" height="315" src="https://www.youtube.com/embed/N1f5rpMDIQ0" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>

What exactly is going on here? Shohei is seamlessly executing a pitch through 5 stages: Wind-up, Stride (Early Cocking), Late Cocking, Acceleration, and Deceleration (Follow Through)[^2].

| Stage | Visual | Description |
| ------- | ------ | ----------- |
| Wind-up|| "...weight is transferred to the drive leg and potential energy is stored in the form of drive knee bending and truncal rotation." [^7] |
| Stride & Early Cocking | | "Pelvis rotates towards target..., producing spinal rotation." [^2] <br><br> "The arm is already externally rotated, horizontally extended, and abducted..." [^6]|
| Late Cocking | |Pelvis has stopped rotating and upper body follows the direction of rotation. |
| Acceleration | |"...arm begins accelerating towards target..." [^7] |
| Deceleration | |After the ball is released, the arm slows down in a safe, controlled manner [^7] |

Throwing a baseball with maximum force clearly takes a lot of skill and practice. How easily can I recreate this, or how much can I maximize my throwing velocity?

***To test this out, I went on a journey to learn how to pitch a baseball. Here's how it started.***

# 2) MY MECHANICS DON'T LOOK AS BAD AS I'D EXPECTED.

<iframe width="560" height="315" src="https://www.youtube.com/embed/Aqpxh-PVuY8" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>

This is my throwing form that I started with. I hadn't received any advice on how to throw and based my throwing solely on whatever life experience I had just generally throwing things. As I talked about in the video, I was pleasantly surprised by the path that my arm and shoulder took. And it wasn't something I consciously thought about, but it felt forceful and right for that kind of motion to occur.

Why did my shoulder want to move this way? How did this specific movement generate enough force to propel the ball forward?

# 3) HUMAN SHOULDER MECHANICS.

The shoulder is one of the body's most flexible joints, and it is capable of much wider ranges of flexion and movement. In fact, the shoulder's range of motion "covers almost 65% of a sphere." [^8] What makes this possible is the many bones, ligaments, tendons, and muscles that work conjointedly to allow for a mechanically flexible and stable joint.

## 3a. In what directions can the shoulder move?

Biomechanically, the shoulder can move along three degrees of freedom [^9]:

| Degree of Freedom | Animation | Types of Movements |
| ----------------- | --------------------------------------------- | ------------------------------ |
| Saggital Plane | *(Shoulder Movement, 2015*)[^9] | Flexion and Extension |
| Transverse Plane | *(Shoulder Movement, 2015*)[^9]|Internal and External Rotation|
|Frontal Plane|*(Shoulder Movement, 2015*)[^9]|Abduction and Adduction|

This range of movement is *incredibly* important because it allows for an *"elastic energy storage"* within the shoulder that leads to power amplification in throwing [^6]. We mentioned that in the "early cocking" stage of a pitch, the arm is already extended, externally rotated, and abducted 90 degrees at the elbow and shoulder. This particular arm position creates a particularly long mass moment arm at the humerus, which causes the arm to lag behind (late cocking) as the torso begins to twist through the stride. When this happens, a **large amount of energy becomes stored in all of the muscles, bones, and ligaments within the shoulder**; this energy is proposed to become the energy that allows the arm to **internally rotate** rapidly at the shoulder -- at rotational speeds that may exceed 9000 degrees per second [^6].

## 3b. What kinds of joints is the human shoulder comprised of?

>*(Veeger & van der Helm, 2007)*[^8]

The shoulder joint is considered to be a "closed chain mechanism" [^8] due to the fact that the shoulder joint is sandwiched in between the scapula (shoulder blade) and the clavicle (collarbone), as show in the image above. These two structures serve as constraints for the movement of the other, which have implications for kinematics and, again, elastic energy storage [^8].

>*(Stabilizing and Strengthening the Shoulder, n.d.) [^10]

Most of the shoulder's mobility comes from:
1. the **glenohumeral (GH) joint**, a ball-and-socket junction between the humerus (upper arm) and the glenoid fossa of the scapula. This accounts for a majority of the range of motion of the shoulder; by itself, it allows the shoulder to elevate by up to 120 degrees and rotate about 135 degrees relative to the scapula [^8].<br><br> Researchers attribute the high range of motion to
a) the relatively small articulation points at the scapula and
b) the looseness in the connective tissue around the joint. This, however, creates the potential for partial shoulder dislocations [^8].
3. the aforementioned interaction between the **clavicle** and the **scapula**, which form a **"scapulothoracic gliding plane."** The movement along this plane is mediated by the **sternoclavicular (SC)** joint and the **acromioclavicular (AC)** joint at the clavicle, and the **scapulothoracic joint** at the scapula [^8]. <br><br>The SC joint frees the shoulder into further mobility by allowing the clavicle to elevate, retract, and rotate [^8].

>:memo: **Do other animals exhibit this kind of mobility?** <br><br> It turns out that this is very unique to humans. Firstly, other vertebrates with shoulder joints do not have the same range of mobility as humans do; for the most part, these joints are limited to a single or few linear planes of motion (i.e., front to back, up to down, etc.) , like some of the organisms in the figure below:
>
><br>*(Veeger & van der Helm, 2007)*
>
>But even our closest genetic living relatives, chimpanzees, don't exhibit quite the level of shoulder mobility that humans do. The location of the human GH joint allows for the humerus to align perpendicularly to the torso with a flexed elbow, which allows for rotational force at the torso to maximally transfer into the shoulder. However, chimpanzees cannot do so because their GH joints are higher relative to their torsos, meaning less efficient transfer of energy through their kinetic chains.
>
><br>*(Roach et al., 2013)*

<br>

---

So my shoulder mechanics are headed towards the right track. Understanding this, I resolved to apply an understanding of elastic energy storage and inertia to my next round of pitches.
<br><br>
However, there was still a glaring problem with my pitching mechanics: **a lack of lower body movement.**

<iframe width="560" height="315" src="https://www.youtube.com/embed/RI5OwRlPs24" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>

<br>As I explained, I noticed that my lower body (feet, legs, hips) had much less movement and force than that of Shohei. This was a problem, as we know that the energy that the shoulder transfers to a thrown object comes from potential, rotational force generated in the lower body. A study by Campbell et. al. found that skilled baseball pitchers tend to activate their leg muscles dramatically during phases 2-4 of a pitch (stride to acceleration) [^3].<br><br> To stabilize this force from my lower extremeties, I had to learn to utilize my glutes.

# 4) THE GLUTE MAX.

In the early cocking/stride stage of a baseball pitch, the lead leg extends forward to increase the distance over which the trunk will extend. As this happens, the stance leg and hip begin to extend and generate maximum rotational force.
<br> However, it's important to note that simultaneously, the gluteus maximus of the stance leg fires to stabilize the pelvis and trunk; without this muscle, there would be no control over this rotational force, which we know will channel into the shoulder complex through the kinetic chain [^12].

>
><br>*(Seroyer et al., 2010)*

<br>

So what exactly does the gluteus maximus look like? And how does it function?

## What is the gluteus maximus?


>*(Gluteal Region: Anatomy [+Video] - Lecturio Medical, n.d.)* [^13]

The **gluteus maximus** is the densest and most powerful muscle in the human body. It has two insertion patterns into the human skeleton:
1. The upper (cranial) part of the gluteus maximus insert into the dorsal (back) crest of the **ilium** (near the sacrum), and
2. the oblique fibers run laterally to the sides of the thigh [^4].

Because of its sheer relative mass and its different insertion points, the gluteus maximus is able to create powerful ***hip extension***, or the straightening out of the hip from a bent position to bring the thigh in alignment with the torso [^4].
>
>*Hip extension.*
>
However, the upper fibers of this muscle also serve to create ***hip abduction***, or move the leg laterally away from the midline of the body.
>
> <br> *Hip abduction.*

>:memo: **Do other animals exhibit this kind of musculature?** <br><br> Among primates, a gluteus muscle of this size and orientation is actually **exclusive to humans**. Firstly, in non-human primates, gluteus muscles are moderate sized, meaning that others are not able to generate nearly as much force as humans can in their hip region. Secondly, the gluteus muscles of non-human primates do not extend up past the ilium, meaning that other primates lack the capacity for the same amount of hip extension at this muscle [^4].

## What does this have to do with throwing?

An EMG (electromyography) study published in 1988 was conducted by Marzke et. al. to determine what bodily movements utilized the gluteus maximus the most. To do this, they measured muscle activation levels in the upper gluteus maximus (where it inserted into the ilium) of six human subjects as they executed four different whole-body motions: walking, throwing, clubbing, digging, and lifting [^11].

Walking did not elicit significant EMG response from the gluteus maximus, indicating that it probably was not an active muscle in the movement.

However, EMG activity spiked when the subjects executed throwing motions.


Markze et. al. makes a comment that's relevant to our discussion here:

>"A striking feature of the sequence in subject 1 was the acceleration of the forelimb that accompanied deceleration of trunk rotation as the arm reached the level of the ear prior to release of the ball (F-G)" [^11].

This echoes what the suggestions for standard baseball pitching form say about lower extremity movement! Markze et. al. conclude that the gluteus maximus is very useful for stabilizing the body when "the hindlimbs are fixed and the trunk is used... for leverage to enhance the force and thus impart greater final velocity to the hand-held tools in throwing, clubbing, and digging..." [^11].

# 5) Final Revisions to My Pitching Mechanics

To put what I learned about shoulder and gluteus maximus mechanics to use, I did two things:
1. Involve my shoulder joint a bit more, letting it decelerate in the late cocking phase to allow for more elastic energy accumulation, and
2. Swing my stride leg further out, externally rotate my hips and feel for my glutes to serve as an "wall" for rotational torsional force to extend off of. In other words, I tried to push off of the gluteus maximus on my stance-leg side.

Here's how it went:

<iframe width="560" height="315" src="https://www.youtube.com/embed/ONWshU3Ulic" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>

This was probably the best throw of 15 that I threw that night. The next day, my shoulder muscles & tendons, my right gluteus maximus, and my right hip adductor were sore in ways that I hadn't felt in a long time, indicating that I was on the right track. As I commented, I think I can attribute my lower body pain to a lack of general training and usage of these muscles. As for my shoulder, I hadn't thrown something in a long time, so even if I am going to the gym several times a week and training my shoulder muscles, the amount of force on my ligaments and tendons was probably an unwelcome shock to my body. However, it was satisfying to experience a little bit of that optimal kinetic chain -- that is, the energy from my hips and legs transferring into my shoulders through my torso.

In hindsight, I should have taken footage of how much further it went, but you'll have to trust me when I say that the balls flew *significantly* further than before.

# 6) SO WHAT DOES THIS HAVE TO DO WITH HUMAN EVOLUTION?

We can point to several things that may distinguish humans from all other animals on Earth:
* Complex language and culture
* Ethics and Morals
* Technological and Scientific Ingenuity
* Ability to make abstractions
* Brain capacity and intelligence

But none of these really explain how the modern human speciated from the evolutionary line of primates. For example, the claim that "the human ability to create complicated and useful technologies caused humans to evolve rapidly" leaves a rather large gap in our reasoning; "Where did this ability come from in the first place?"

" What we are looking for is a more "ultimate cause" of the evolution of our ancestors into the modern human. Bingham & Souza's Theory of Social Coercion seeks to explain this.

## Non-Kin Costs of Cooperation

>"Specifically, for coercion to be an individually self-interested behavior, its immediate costs must be less than its immediate benefits. If its costs are greater than its benefits, coercion becomes a self-defeating behavior under almost all circumstances" [^1].

Organisms will only cooperate and form mutualistic social groups to the extent that the cost of cooperating is outweighed by the benefits of doing so. For most organisms, cooperating will always be more costly than beneficial by design because of the nature of **proximal conflict.**
Almost all animals are proximal killers, which means that if one were to attempt to enact the threat of violence, it would be putting itself at risk of receiving the same harm. This risk of receiving proximal harm exists even in hypothetical cohorts of animals that may try to work together to fight off thieves trying to steal some prey; at the end of the day, it is less expensive to just let the thief take its undeserved share of the meal:
>"Adult-on-adult coercion is just too expensive for all but the strongest and the strongest can often better use their advantage to steal than to enforce cooperation. Each individual does his/her best to pursue self-interest without helping other, non-kin individuals. All other behaviors do worse under natural selection" [^1]

But in situations where non-kin conflict of interest becomes more expensive than non-kin cooperation, animals will choose the latter. Humans have effectively accomplished this.

## The First Conspecific, Kinship-Independent Cooperation

Humans are able to evade the cost of proximal conflict by breaking the model for conflict itself. Humans do this by coming ***remote killers*** [^1]. When humans gained the ability to kill non-kin conspecifics from a distance, they drastically lowered the cost of cooperating with others in enacting a coercive threat to thieves and cheaters. And as a result:
>"Individually self-interested remote killing animals can afford the costs of self-interested coercion against conspecific adults. A by-product of this coercive threat is the suppression of non-kin conflicts of interest. Proximally killing animals cannot afford these costs and rarely cooperate with non-kin. As a result, the first remote killing animal that evolved on planet Earth should have quickly gone on to evolve kinship-independent social cooperation" [^1].

Humans were able to become remote killers when they developed the ability to throw projectiles at lethal velocities. And this is why we've been exploring throwing as a uniquely human ability.

When humans became able to form large-scale cooperative groups, they unlocked the potential to develop other uniquely human traits, such as culture, extensive language, technological advancements, and ethics and morals. But it all started from simply being able to cooperate.

# 7) Conclusions: Lethal Throwing as a Uniquely Human Trait

The goal of this exploration was to dive deeper into the uniquely human ability to throw projectiles lethally. No other animal on Earth can replicate throwing to the same extent, as explored in the anatomy of the shoulder and the gluteus maximus; even chimpanzees, which are humans' closest modern genetic relatives, lack the anatomical and biomechanical features that contribute to lethal throwing.

The fact that this ability is exclusively human lends itself to Social Coercion Theory, that is, that the cost and benefit dynamics of being a remote killer effectively makes wide-spread non-kin cooperation inexpensive enough to be possible, making humans the first and only animals that can cooperate on such a wide scale.

# References
[^1]: Bingham, P. M., & Souza, J. (2009). Death from a distance and the birth of a humane universe : human evolution, behavior, history, and your future. Booksurge.

[^2]: Calabrese, G. (2013). PITCHING MECHANICS, REVISITED CORRESPONDING AUTHOR. The International Journal of Sports Physical Therapy |, 8(5). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3811736/pdf/ijspt-10-652.pdf

[^3]: Campbell, B. M., Stodden, D. F., & Nixon, M. K. (2010). Lower Extremity Muscle Activation During Baseball Pitching. Journal of Strength and Conditioning Research, 24(4), 964–971. https://doi.org/10.1519/jsc.0b013e3181cb241b

[^13]: Fidoe, S. (2013). The Hip Bone - Ilium - Ischium - Pubis - TeachMeAnatomy. Teachmeanatomy.info. https://teachmeanatomy.info/pelvis/bones/hip-bone/

[^4]: Jouffroy, F. K., & Médina, M. (2006). A Hallmark of Humankind: The Gluteus Maximus Muscle. 135–148. https://doi.org/10.1007/0-387-29798-7_10

[^5]: Kress, M. (2020). Lanchester Models for Irregular Warfare. Mathematics, 8(5), 737. https://doi.org/10.3390/math8050737

[^11]:Marzke, M. W., Longhill, J. M., & Rasmussen, S. A. (1988). Gluteus maximus muscle function and the origin of hominid bipedality. American Journal of Physical Anthropology, 77(4), 519–528. https://doi.org/10.1002/ajpa.1330770412

[^6]: Roach, N. T., Venkadesan, M., Rainbow, M. J., & Lieberman, D. E. (2013). Elastic energy storage in the shoulder and the evolution of high-speed throwing in Homo. Nature, 498(7455), 483–486. https://doi.org/10.1038/nature12267

[^12]: Seroyer, S. T., Nho, S. J., Bach, B. R., Bush-Joseph, C. A., Nicholson, G. P., & Romeo, A. A. (2010). The Kinetic Chain in Overhand Pitching: Its Potential Role for Performance Enhancement and Injury Prevention. Sports Health: A Multidisciplinary Approach, 2(2), 135–146. https://doi.org/10.1177/1941738110362656

[^9]:Shoulder Movement. (2015, April 26). Www.youtube.com. https://www.youtube.com/watch?v=5pjk_yW-JsU

[^10]:Stabilizing and Strengthening the Shoulder. (n.d.). Www.racmn.com. Retrieved July 20, 2023, from https://www.racmn.com/blog/stabilizing-and-strengthening-the-shoulder

[^7]: Trasolini, N. A., Nicholson, K. F., Mylott, J., Bullock, G. S., Hulburt, T. C., & Waterman, B. R. (2022). Biomechanical Analysis of the Throwing Athlete and Its Impact on Return to Sport. Arthroscopy, Sports Medicine, and Rehabilitation, 4(1), e83–e91. https://doi.org/10.1016/j.asmr.2021.09.027

[^8]: Veeger, H. E. J., & van der Helm, F. C. T. (2007). Shoulder function: The perfect compromise between mobility and stability. Journal of Biomechanics, 40(10), 2119–2129. https://doi.org/10.1016/j.jbiomech.2006.10.016