So currently in my speculative evolution scenario, I have a creature with an elongated trunk that it uses for rock climbing. This species transitions to a savannah like lifestyle and I was wondering if there was a gait that could incorporate balancing on their leg-like trunk at any point? any help would be appreciated

  • $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Jul 4, 2023 at 4:19
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    $\begingroup$ Striding on its noses there comes the nasobame, with its young in tow. It isn't yet in Brehm's, it isn't yet in Meyer's, and neither in Brockhaus'. It trotted out of my lyre when it came first to light. Striding on its noses thereon (as I've said above), with its young in tow, there goes the nasobame. (Christian Morgenstern, The Nasobame, 1895.) (See also Rhinogradentia.) $\endgroup$
    – AlexP
    Jul 4, 2023 at 4:23
  • $\begingroup$ Bipedality implies a very evolved brain, as you need to constantly monoitor your mass center to not get off your area of standing. Quadrupedality evolved far earlier than even the rudimentary brain, since standing on three legs and moving the fourth does not need such strict movement and balance control. I would wonder how did your nosebames' ancestors lose their front limbs while living in rocks, having extra support is very beneficial in that environment. $\endgroup$
    – Vesper
    Jul 4, 2023 at 4:42
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    $\begingroup$ I suspect the reason you're not getting answers is that no one wants to come right out and tell you "no." A monkey's prehensile tail exists primarily to balance the body. It's not used for running and some species have developed ways of using it for other things like holding on or help climbing. But your trunk isn't providing that advantage. Worse, the body is off-balance because of it - unless it's too small to be useful as a third leg (which would almost be necessary if it's a primary manipulator). I suspect you're doing things (*Continued*) $\endgroup$
    – JBH
    Jul 5, 2023 at 0:15
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    $\begingroup$ ... backwards by imagining a cool-looking creature and now you're trying to find reasons for the cool-looking features to exist. I could imagine a bird with a long beak & tongue evolving into your trunk & biped. But such a creature has no need of the trunk to walk/jog/run. It might use it like a hand/arm to anchor to a tree or building corner to help pivot while running. But the only reason for using it in regard to gait is because the creature isn't biped - unless you're thinking gorilla/chimp? Evolution would favor arms over trunks for that, but it might work. $\endgroup$
    – JBH
    Jul 5, 2023 at 0:18

2 Answers 2

  1. Quadripedal Gait with Trunk Balancing:

    • Initially, the creature might use all its limbs (including the trunk) for rock climbing, leveraging the trunk's flexibility and grip to maneuver on rocky surfaces.
    • As the species transitions to a savannah-like lifestyle, it could adopt a quadripedal gait where the trunk is primarily used for balance and stability. The front limbs would still be important for grasping and climbing.
  2. Bipedal Gait with Trunk Balancing:

    • The creature could use a bipedal gait on the savannah, with the trunk acting as a balancing appendage. The trunk would help maintain stability during locomotion, especially during sudden turns or when traversing uneven terrain.
  3. Serpentine-like Locomotion:

    • The creature might exhibit a serpentine or undulating locomotion, similar to snakes. The trunk could be used for gripping and anchoring onto rocks or trees, while the rest of the body moves in a wave-like motion to propel itself forward.
  4. Hopping or Vaulting:

    • The creature could use a hopping or vaulting gait, where it pushes off with its limbs and uses the trunk to aid in balance during mid-air maneuvers. This would be useful for crossing gaps or jumping between rocks.
  5. Suspended Swinging:

    • The creature might have the ability to swing from its trunk-like appendage, similar to gibbons swinging from tree branches. This swinging motion could help it navigate between trees or large rocks efficiently.

The choice of gait will depend on various factors, including the creature's anatomy, the environment it inhabits, its specific ecological niche, and the types of locomotor challenges it faces. Additionally, considering the evolutionary context and gradual transitions from rock climbing to a savannah-like lifestyle will help in creating a plausible and engaging speculative evolution scenario.


I am assuming that the evolution of a trunk to help with rock climbing would result in a fairly strong appendage. While it would offer little advantage in forward mobility, it could be used to stop more quickly (as five points of contact will have more friction than four), to change direction faster (as the trunk provides an additional bracing point to help pivot, or could be used to grab onto an anchor point and swing the creature in a new direction), or as a method of quickly jumping backwards away from danger. If the creature became front heavy, it might need to use the trunk to move forward. Think of a horse with a much larger head. The trunk stabilizes the head while the body moves forward. Then the head moves forward and balances on the trunk again.

Does your creature need to be able to use it for locomotion? Is there a story need for it? Would the story be different without that trait? A throw away line about the creature having an odd gait due to its trunk can be enough to satisfy an audience as their brain produces possibilities and fills in the mental image.

You need to determine if the trunk offers an evolutionary advantage or not. If so, then what is the advantage? Adapt it to better suit that role. If not, then assume it will atrophy over time and eventually have less of an impact on gait. Evolution does not work towards a specific form. It weeds out forms which are less competitive than the alternative. The environment will drive the adaptation. It takes energy to grow muscles. If that muscle group is no longer being used, those with smaller trunks would use less energy and thus have more for their overall survival. This is not unlike fish and other cave dwellers which lose their ability to see, as it offers no survival advantage.

If you want to keep the trunk but evolve it, you can look at animals like the narwhal for ideas on odd adaptations. The narwhal “horn” is actually a tooth. Perhaps your creatures evolve so that their trunk becomes shorter, stouter, and long nails grow from the end. It then uses it to defend against predators or for mating rituals. If moving from a mountainous region to a plains biome, it could use its trunk to shield its eyes from the brighter sun. Wrapping the trunk around the top of the head might balance the weight enough to prevent gait interference. Anything which has a detrimental impact on survival will quickly cause change in a population. Neutral and/or beneficial mutations would survive and become dominant traits.


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