User:Alkunzle/sandbox

= Facultative bipedalism outline =

Intro paragraph
Current: A facultative biped is an animal that is capable of walking or running on two legs, often for only a limited period, in spite of normally walking or running on four limbs or more. The switch to facultative bipedalism often occurs when an animal begins to run at high speeds, notably in many lizards, such as the basilisk lizard, and in some cockroaches. Low-speed facultative bipedality is less common; the gibbon, a primate with an anatomy highly specialized for arboreal locomotion, can walk bipedally in trees or on the ground with its arms raised for balance.

Edit: A facultative biped is an animal that is capable of walking or running on two legs, often for only a limited period, in spite of normally walking or running on four limbs or more. It differs from obligate bipedalism in that facultative bipeds use four limbs as their primary method of locomotion, only occasionally becoming bipedal, often for a specific purpose. Primates and lizards are the most common animals that engage in facultative bipedalism–this behavior has been observed in several families of lizards, including Agamidae, Crotaphytidae, Iguanidae and Phrynosomatidae, and multiple species of primates, including sifakas, capuchin monkeys, baboons, gibbons, and chimpanzees. There are multiple different types of bipedal motion, with different facultative bipeds using different types. This corresponds to the different reasons various species have for engaging in facultative bipedalism. In primates, bipedalism is often associated with food gathering and transport. In lizards, whether bipedal locomotion is an advantage for speed and energy conservation or whether it is governed solely by the mechanics of the acceleration and lizard's center of mass has been debated. Facultative bipedalism is often divided into high-speed (lizards) and low-speed (gibbons), but some species can not be easily categorized into one of these two. Facultative bipedalism has also been observed in cockroaches and some desert rodents.


 * Definition - they have a pretty solid working definition in the previously established introduction. Make it more specific in terms of both contexts in which bipedalism is used and the high/low speed difference that it touches on, as well as mentioning the different types
 * Overview of types of species (from what we have below - primates and lizards)
 * Brief mention of different situation in which they perform facultative bipedalism (i.e. food gathering)
 * Distinguish from obligate/habitual bipedalism in the fact that it is not done all the time

Types of Bipedal Locomotion
This is a very basic and simple overview that is currently lacking from the page. Having this will increase the clarity of the definition and provide context for the reader.

●      Walking – evenly spaced gait

●      Running – has a period where both feet are off the ground

●      Skipping  - both feet are off the ground and then hit the ground right after each other, trailing foot changes each step

●      Galloping – similar to skipping, but the trailing foot stays the same in each step

Facultative Biped Species
Obviously, naming the species that use facultative bipedalism and describing their behavior is the most substantial part of this page. We’ve separated it into primates and lizards because those were the two main categories that we identified through our research, and are mentioned on the current page. Having this level of detail about bipedalism in each of these species will greatly enhance the utility of the page.

Facultative Bipedalism in primates
In which species bipedalism is found (homo - human, hylobates - gibbons, pan - chimpanzees and bonobos, pongo - orangutans, gorilla, propithecus - sifaka)

Lemurs
-Propithecus bipedalism - Sifakas


 * Arboreal vertical clingers and leapers, will locomote bipedally on the ground
 * Walking or bipedal gallop
 * Comparisons to other primates
 * Hip joint: humans have extended hip joint, pan and propithecus have flexed hip joint, Hylobates has most flexed hip joint
 * Knee joint: propithecus is similar to other primates, though humans flex the knee joint less
 * Propithecus and humans are the only ones to utilize the skipping/galloping type, pan and Hylobates mostly walk
 * Sifaka have an anatomy that is specialized for vertical clinging and leaping but also makes them obligate bipeds on the ground to conserve energy.

-Ring-tailed lemurs (lemur catta)


 * Can be arboreal and terrestrial, when terrestrial are quadrupedal 70% of the time and bipedal 18%, more than other other genus lemur
 * When bipedal, they hopped or walked

Monkeys
-Capuchin monkey bipedalism


 * Arboreal quadrupeds, will locomote bipedally on the ground
 * Spring-like walk, no running (with aerial phase) - the faster they go, the less they wobble
 * Capuchins do not employ a pendulum-like gait. In humans, this allows recovery of energy through the interchange of kinetic and potential energy. Without this in capuchins, energy costs are high.
 * Pendulum-like walking may be the distinction that led to human bipedalism
 * One of the most successful facultative bipeds - frequent and skillful, particularly in regards to load carrying


 * Describe the detailed kinetics of their motion

-Baboons (papio)


 * Olive baboons- described as a quadrupedal primate, but bipedalism is observed occasionally and spontaneously in captivity and in the wild
 * Immature baboons appear to be more bipedal than adults
 * Bipedal postures and locomotion in infants, although infrequent, appear to distinguish them clearly from adults
 * Go into more detail about the specific quantitative data

Apes

 * Apes in closed forest habitats are more bipedal than chimps and baboons, stationary or moving
 * Terrestriality is not a spur to bipedal behavior

-Gibbons (hylobates)


 * Anatomy that is specialized for vertical clinging and leaping but also makes them obligate bipeds on the ground to conserve energy.
 * Low speed
 * Vertical climbing develops similar hip and knee joint extensions to that used for bipedal locomotion
 * Similar use of 3 primary back muscles to chimpanzees and humans

Gibbons (of the genus Hylobates) are low-speed obligate bipeds when on the ground. Because they usually move through trees, their anatomy has become specialized for vertical clinging and leaping, which uses hip and knee joint extensions that are similar to those used in bipedal motion. They also utilize three back muscles that are key to bipedal motion in chimpanzees as well as humans.

-Chimpanzees


 * Excessive tilt and rotation compared to humans
 * Exhibit bipedalism more often when carrying valuable/commodity resources
 * Can carry more than twice as much when walking bipedally as opposed to quadrupedally
 * Primarily used for food gathering/transporting purposes


 * Among chimpanzees, as well as baboons, bipedalism has been linked to feeding - both on the ground and aloft when feeding from fruit trees; foraging in short trees with both feet on the ground allows for individuals to reach higher into the trees
 * Posture feeding hypothesis

-Australopithecus anatomy in relation to bipedalism


 * Pelvis and lower body morphology indicate bipedalism
 * Also morphology that indicates less than bipedal conditions
 * Australopithecines experienced high pelvic and femoral stresses - small diameter spine, wide hips, short legs require more energy per unit distance to operate

-Other: Gorillas and orangutans are also facultative bipeds

Facultative bipedalism in lizards

 * Lots of debate over whether lizard bipedalism confers any advantages (faster, less energy consumption)
 * In lizards, the full benefits of bipedal running have not yet been identified. Rather, it appears as if bipedal running is due to acceleration. When the hind limbs build enough power, a strike from the hind limb opens the lizard’s trunk angle and shifts its center of mass; this, in turn, increases front limb elevation
 * In modeling, a very specific number of steps and rate of acceleration leads to the exact shift in the center of mass that allows the elevation of the front limbs; too fast and the center of mass moves too far back and the lizard falls over backward; too slow and the front limbs never elevate but real lizards adjust their movements (forelimbs, tail) to increase stretch of bipedal locomotion and are better at it than the model suggests
 * Development due to simple acceleration/center of mass physics but does confer an advantage, so was exploited and the behavior evolved
 * Passive engagement minimizes energy use to keep the front limbs on the ground
 * Maybe makes maneuvering easier/better, helps increase speed → advantage but not a cause
 * Doesn’t increase speed but does increase acceleration - acceleration thresholds at which the lizards begin running bipedally are lower than the Aerts model predicts → the lizards may be actively trying to run bipedally rather than passively going with it, so there may be some other advantage that we haven’t found yet

In lizards, facultative bipedalism occurs as a result of rapid acceleration caused by the location of the lizards’ hind legs which induces a friction from the ground to produce a reaction force on the rear legs. When the hind limbs build enough power, a strike from the hind limb opens the lizard’s trunk angle and shifts its center of mass; this, in turn, increases front limb elevation, allowing bipedal locomotion over short distances. When modeled, an exact number of steps and rate of acceleration leads to an exact shift in the center of mass that allows the elevation of the front limbs: too fast and the center of mass moves too far back and the lizard falls over backward, too slow and the front limbs never elevate. However, this model does not account for the fact that lizards may adjust their movements using their forelimbs and tail to increase the range of acceleration in which bipedal locomotion is possible.

There is some debate over whether bipedalism in lizards confers any advantage. Advantages could include faster speeds to evade predators, or less energy consumption, and could explain why this behavior has evolved. Research has shown that bipedal locomotion does not increase speed but can increase acceleration. It is also possible that the behavior developed as a physical property of the lizards' movement only because of the acceleration of the center of mass, and passive engagement with this physical motion minimizes the energetic cost that it would take to keep the forelimbs on the ground. Recent research has shown that the actual acceleration at which lizards begin to run bipedally is lower than the previous model predicted, suggesting that lizards actively rather than passively engage in bipedalism and thus, the behavior may confer some advantage that has not yet been identified. Alternatively, while the origin of the behavior may have been due to physical motion, it may have conferred an advantage such as easier maneuvering that was then exploited.

Evolution of bipedalism
Because a lot of the studies concerning the mechanics and such of bipedalism are framed in the context of how bipedalism evolved in humans, we think it is important to address the evolution of facultative bipedalism on this page. The evolution of behaviors, especially those that are related to anatomy and structure, is crucial to understanding what purposes they serve. The details provided in the section above give the necessary information to put this section in context of how bipedalism works mechanically.

-Origin of bipedalism in dinosaurs


 * Facultative bipedalism leading to obligate bipedalism in dinosaurs
 * Using studies of lizards to reveal the conditions in which bipedalism arises
 * Bipedalism as a method of increased speed through larger hind limb muscles

-Origin in primates


 * Separate in humans, bonobos, and gibbons
 * Evolutionary explanation of development and/or selective pressure often linked to load-carrying - chimpanzees, bonobos, macaques, capuchins, baboons : Either selective pressure or significant advantage; affects limb mechanics and anatomy as load carrying causes increased force on the lower limbs ; chimpanzees being able to carry more - in uncertain environments with potentially unavailable commodities, walking bipedally to carry more is advantageous
 * Various arboreal adaptations also likely made bipedalism advantageous - specific types of a set of behaviors can illustrate parts of the evolutionary path


 * Bipedalism possibly developed from vertical climbing and/or brachiation: brachiation changes arm structure/purpose to make quadrupedal walking difficult, causing a shift to bipedalism (like with gibbons)
 * Hip and thigh muscles involved in bipedal walking of facultative bipeds often resembles quadrupedal walking less than human walking, but when it doesn’t look like quadrupedalism, it looks like vertical climbing
 * Bipedalism more often resembles climbing than facultative bipedalism
 * Biomechanics contributes directly to an understanding of both morphology and fossil records

Studying the biomechanics of motion directly contributes to understanding the morphology of both modern primates and fossil records. Bipedal locomotion appears to have evolved separately in different primates including humans, bonobos, and gibbons. The evolutionary explanation for the development of this behavior is often linked to load-carrying in chimpanzees, bonobos, macaques, capuchin monkeys, and baboons. The ability to carry more materials may be either a selective pressure or a significant advantage, especially in uncertain environments where commodities must be collected when found as they can potentially become unavailable. Load carrying affects limb mechanics by increasing the force on the lower limbs, which may affect the evolution of anatomy in facultatively bipedal primates.

Various arboreal adaptations may have affected the evolution of bipedalism as well. Vertical climbing and brachiation changes the structure and purpose of the forelimbs, making quadrupedal walking more difficult and contributing to the shift to bipedal locomotion. Gibbons and sifakas are examples of this: their movement through trees makes quadrupedal walking difficult, resulting in bipedal walking and galloping, respectively. Arboreal adaptations making bipedalism advantageous is supported by research that shows that hip and thigh muscles involved in the bipedal walking often most resemble those used in climbing.

In lizards, bipedal running developed fairly early in their evolutionary history. Fossils suggest this behavior began approximately 110 million years ago. Facultative bipedalism may also promote adaptive radiation.

= Horse behavior article evaluation =


 * Sections are poorly organized and all over the place - consolidate some of the sections
 * Some of them aren't important enough to have their own sections
 * Reorganize/rank sections
 * In the talk section, someone thinks the opening paragraph needs work
 * "accidentally harm people" some of this just doesn't seem like it was written by people familiar with horses, regardless of sources
 * Most of the talk page activity happened over a year ago, although it is ranked as a top priority of a wikiproject
 * Copy edit this entire thing - some of it is poorly written, even if it's not explicitly wrong
 * Check sources, because there are a lot of arguments in the Talk section over whether or not certain things are true and whether the citations have been interpreted correctly
 * Find more sources for a lot of it - a lot of things aren't cited
 * Some things have been determined more by common knowledge of those who work with horses and have not been formally studied. What do you do about that information?

= Weaving article evaluation =


 * There is very little information here. I will embellish some of it that is already cited, and check those citations.
 * It is of Low importance and Start class, although it is part of a wikiprojects
 * The only discussion in the Talk section is concerning its tag as a veterinary subject