Okay, so I was creating a cold-blooded humanoid species (for a story, I'm no scientist) and ran into a problem with some of my logic.

Because of their obvious issues with overheating, these lizardmen couldn't be pursuit predators like humans proper can with their miraculous ability to sweat. So I adapted them for ambush tactics instead. After all, because they don't waste nearly as much energy with homeostatic systems, they could wait around until prey showed up instead of having to hunt it down like a common mammal.

With this in mind, I decided to utilize the broad bodies I gave them for sunning themselves to make them really good at throwing weapons. After all, javelins and throwing clubs are a great way to kill prey without putting yourself at risk. Plus, it would give the species a much needed edge in combat against the superior stamina and environmental resilience of humans (and I think throwing weapons are cool).

So here was my logic:

Broad shoulders, long arms, and very elastic tenons were supposed to give this species the ability to throw objects at greater velocities than humans ever could due to leverage. Seemed open and shut at the time.

However, I was watching this video by the god-amoungst-men Zootier and he pointed out that the qualities I assumed would give them an advantage would actually make them worse at throwing things. In short, it's short arms and superior balance that allows humans to make fifty yard passes while other apes can barely qualify for a softball team. The long arms and broad torsos of my humanoid reptiles just seem to make them more prone to falling over whenever they put their weight behind their pitches.

If my logic is flawed (which it seems it is), what changes do I make to make these creatures capable of throwing objects at greater velocities than humans?

In case it is relevant, their accuracy isn't intrinsically better than a humans, but these reptiles tend to practice a lot to make the most of their fastball advantage.

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    $\begingroup$ You could shorten their arms, give them better balance, & find other ways of increasing their bodily area to sun themselves. Say, by having web-like structures between their arms & legs or inflatable crests on their heads. $\endgroup$ – a4android Jun 21 '18 at 4:54
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    $\begingroup$ Could you sketch the argument this Zootier was making? An AtlAtl will greatly improve the spear-throwing capabilities of any human, and it is essentially a longer arm. Only thing to keep in mind is that with these kinds of movement the 'hand' (where the tip of the atlatl is) gets subjected to pretty strong g forces, which might need extra attention in creature design to avoid bleeding, i.e., from the nails. ... And ... 'Superior balance' is connected to longer arms how? $\endgroup$ – bukwyrm Jun 21 '18 at 5:17
  • $\begingroup$ Paleonthological findings seem to demonstrate that several lizard species were able to go pursuit after a prey. So you don't need to worry at all: just say that they evolved from a runner species like the velociraptor and they're all set for longer-distance chases. $\endgroup$ – Valerio Pastore Jun 21 '18 at 6:03
  • $\begingroup$ Certainly you don´t have overheating problems for cold-blooded creatures! The opposite is true - if it gets to cold, they tend to get slow! $\endgroup$ – Daniel Jun 21 '18 at 7:40
  • $\begingroup$ Or to be more precise: T-Rex was most likely a pretty good pursuit predator ... $\endgroup$ – Daniel Jun 21 '18 at 7:42

Accelerating anything means using force on it, for a period of time. More muscles, more force, case closed? No.

  • Muscles do not magically produce force, it is biochemical reactions that do the -pun intended- heavy lifting. These limit the maximal contraction-velocity.
  • This is where levers and other kinds of force/way exchanges come into play - you have the slow muscle go way x with force F (at ideal velocity) then some other point P goes way x*n with Force F/n. If that happens in the same time, P will be faster by factor n.
  • You just need to make sure to supply enough Force so that F/n is still enough to actually acelerate the mass at point P to that velocity.
  • Elasticity in the system can be bad or good, depending on the specifics of the design. For instance an elastic element like a bow enables us to slowly but with high Force draw, and then release in an instant. This is also possible in-body. On the other hand a too-elastic sinew will 'eat' all the force, and might not release it until the missile has already left the hand.

So your long-armed reptiles may be better or worse at throwing, but the best- designed long arm will always be better than the best-designed short arm - All of the above factors like sinew elasticity, best muscle contraction velocity/force combination, leverage etc. have to be exactly right and are interdependent and their efficacy is dependent on factors like missile weight, throwing angle, accuracy, etc. That's why some people suck at throwing, even if they train. Maybe most of your lizard folk can hurl a 10kg uber-spear into 100m distant targets like a meteor, but at the same time suck at softball.

Addition : There even is a phd written on that very subject (well, not lizard-folk) - possibly more than one, but i found an accessible one: Julia Marie Maki, "The Biomechanics of Spear Throwing: An Analysis of the Effects of Anatomical Variation [...]" - it is 300+ pages, but a few insights are shared on the first few that i skimmed:

  • Spear throwing is not equal to ball throwing (elbows are out of the picture for spears).
  • Spear throwing has many factors, but reliable predictors are torso- and leg-anatomy.
  • Broad shoulders are beneficial for Spear throwing.
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  • $\begingroup$ I was going to say something similar. Apes have longer arms, but worse balance and they are not very good at throwing things. There's no reason why another species could not have both longer arms and similar balance than humans, being better than us at throwing things. $\endgroup$ – Rekesoft Jun 21 '18 at 8:48
  • $\begingroup$ "heavy lifting" - groan $\endgroup$ – Neil Jun 21 '18 at 13:04
  • $\begingroup$ I'll be honest, I'm not entirely sure what you are saying. As far as my limited understanding goes, you're saying that if you put more force into an object it will go faster? And the sinew thing is a neutral factor, I think? I'm more than a little confused. $\endgroup$ – Pinion Minion Jun 21 '18 at 13:39
  • $\begingroup$ @PinionMinion, exactly. Force along a path is work (energy) ( F*s=E). For a given mass in throwing, this energy would translate into velocity: E = 1/2 * m * v^2. Note that because of the square velocity, if you want double velocity, you need to produce four times the energy, meaning you either need to put in four times the force, or four times the path, or a combination (double force, double path-length). So leverage seems to not change a thing (double the force but halve the path = same energy), until you take into account that muscles cannot move faster than a certain value. $\endgroup$ – bukwyrm Jun 22 '18 at 11:20
  • $\begingroup$ About the elasticity: It's not neutral as in: "Magically give this guy less elastic sinews, and he'll be just the same thrower" - Biomechanics would reveal what happens (either better or worse) but more like: "give those two engineering teams access to differently elastic sinews, Team A gets the gummy ones, Team B gets the taut ones - all the other parts (muscles, bones,...) being equal for the teams - and nobody'll be able to predict which Team creates the better throwing creature. " ---- with arm length that is not true: the team constrained to shorter arms would almost surely lose. $\endgroup$ – bukwyrm Jun 22 '18 at 11:25

Tools can make them capable of achieving that, without changing their bodies.

Let's start with a simple example: throwing a ball.

If you use your hand and arm, you can throw it to a certain distance. Now, use something like this

ball thrower

and you will be able to launch the ball farther and faster.

With some modification you can use a similar tool to launch a spear. This tools was also used by our ancestors, and is called atlatl

An atlatl is essentially a stick with a handle on one end and a hook or socket that engages a light spear or “dart” on the other. The flipping motion of the atlatl propels a light spear much faster and farther than it could be thrown by hand alone.

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    $\begingroup$ ... Or for Spears: "Atlatl" $\endgroup$ – bukwyrm Jun 21 '18 at 4:48
  • $\begingroup$ @bukwyrm, thanks, added that in the answer $\endgroup$ – L.Dutch - Reinstate Monica Jun 21 '18 at 5:20
  • $\begingroup$ I appreciate the answer, but I am more interested in biological solutions. After all, using tools would remove that advantage over humans that I think the lizardmen need. $\endgroup$ – Pinion Minion Jun 21 '18 at 13:27
  • $\begingroup$ @PinionMinion I would take this answer as a real-world example where having longer 'arms' advantages throwing. the device simply extends the length of the arm artificially for humans. $\endgroup$ – GOATNine Jun 22 '18 at 13:07

Throwing is not about the length of the arm but about how the shoulder is structured, a chimp is incapable of the the full rotation an arm goes through during an overhand throw. Basically if your lizardmen can put their shoulder through a full 360 rotation then they can throw. This feature only evolved in humans recently once climbing was no longer important. the anatomical needs for throwing is actually well studied.

the hard part is making them better than humans who are the best throwers in existence.you might want to consider if the tail could contribute somehow, maybe as a cantilever. If your really need an advantage over humans pebbled scaly skin will function like armor which will be a noticeable advantage.

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If you want to get really creative, why not give them the sort of biological spring mechanism mantis shrimp use to break open clam shells (accelerating their limbs at over 100,000m/s and striking with enough force to cavitate the water around the strike which produces a measurable aftershock). Have a look into it. They're mindblowingly powerful.

You'd need some pretty advanced musculature around them to bring finesse and accuracy to such an adaptation, but if you could then you'd have a significant range and power advantage against a human missile-thrower.

Whatsmore, you'd also pack a fearsome punch in a close quarters fight (although likely at the cost of endurance/frequency of repeat strikes). It'd make for some pretty interesting combat dynamics between humans and your biological-catapult lizardpeople. I'd expect the lizardperson try to hold off until it can best use its advantage? Would a human try to provoke the lizardperson to strike multiple times, tiring it, or try their best to dodge the initial ferocious strike and then strike back before they can recover?

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