User:Koporc.3/sandbox

Topic: The Evolution of the human foot

McKeon, Patrick O., Jay Hertel, Dennis Bramble, and Irene Davis. "The Foot Core System: A New Paradigm for Understanding Intrinsic Foot Muscle Function." (2014): n. pag. Web. 14 Sept. 2014. This article talks about the importance of the arch in the foot. It covers the basis for the evolution of it which was because hominids were using their feet more for walking upright.

Wright, W. G., Y. P. Ivanenko, and V. S. Gurfinkel. "Foot Anatomy Specialization for Postural Sensation and Control." J Neurophysical (2011): n. pag. Web. 14 Sept. 2014. This article talks about how the foot evolved for how it was to be used. In it is says that the human foot evolved a unique design or propulsion and support and how the arch and toes especially play an important role

Bates KT, Collins D, Savage R, McClymont J, Webster E, Pataky TC, D’Aout K, Sellers WI, Bennett MR, Crompton RH. 2013. The evolution of compliance in the human lateral mid-foot. Proc R Soc B 280: 20131818. http://dx.doi.org/10.1098/rspb.2013.1818 This article talks about the fossil evidence of for longitudinal arches in the foot. It discusses the importance of this find as it is used to structure the origin of human bipedalism. It states that the structure of the foot, from the arch, flexibility, and the distribution of weight on the foot are all important.

Ward, Carol V., William H. Kimbel, and Donald C. Johanson. "Complete Fourth Metatarsal and Arches in the Foot of Australopithecus Afarensis." Science (2011): n. pag. Web. 15 Sept. 2014. This article discusses how the human foot had to evolve to be able to sustain a life upright on two feet. Things such as shock absorption during striding bipedal gait

DeSilva, Jeremy M., and Zachary J. Throckmorton. "Lucy's Flat Feet: The Relationship between the Ankle and Rearfroot Arching in Early Hominins." Plos One (2010): n. pag. Web. 15 Sept. 2014. Discusses how the hominin foot evolved from being a grasping appendage to being a stiff propulsive life lever. According to the article, the “central thing to this transition which was the development of the longitudinal arch which helps store elastic energy and stiffen the foot during bipedal locomotion”. It also talks about how it is hard to obtain fossil evidence for this because soft tissue doesn’t fossilize.

Assignment #2

https://en.wikipedia.org/wiki/Bipedalism

This article is great in many ways but can be improved in some parts. For one, it could mention how one of the purposes of the human foot is for propulsion. It talks about how it was built to support weight and maintain balance, but it does not mention the importance of shock absorption. If it weren't for shock absorption our joints could be worn down and not last as long. Also, the article could mention how the human foot evolved under selection to be a flexible rather than stiff structure. Bates KT, Collins D, Savage R, McClymont J, Webster E, Pataky TC, D’Aout K, Sellers WI, Bennett MR, Crompton RH. 2013. The evolution of compliance in the human lateral mid-foot. Proc R Soc B 280: 20131818.

06:26, 1 October 2014 (UTC)~Christine K.

Article that I added informaiton to the talk page, titled "Suggestions-CK"
https://en.wikipedia.org/wiki/Talk:Bipedalism

== FINAL DRAFT OF PAPER ==

The beginning of bipedalism is a story which goes back millions of years, and can be understood by one of its important mechanisms: the foot. The significance of the foot and the muscles and bones involved are what support our body to help us stand, walk, and run. How the foot is shaped is an essential part to how humans today can move around. There has been extensive research done on the structure of the foot and how it has developed over millions of years. One such fossil which has gained immense popularity and has had research done on it is that of Ardipithecus ramidus which is species of hominoid fossils discovered in 1994 in Ethiopia (“Ardipithecus ramidus”). Another important factor about the foot is the extensive morphology involved in the foot including the importance of the three arches we now have to where our big toe is located. As hominids began to use their feet more for bipedal locomotion, the foot had to change with the demands placed on it in order to be a functional tool. The research conducted on the evolutionary history of the human foot has given a new insights to our history as a species, our bipedal locomotion, and how important the foot, its shape, and function is to us. Evolution is a process that can take place over millions of years; we rely on fossil evidence in order to find out what life was like and what organisms were present millions of years ago. Finding fossils of Hominin feet can be a difficult task, and it is even more problematic because soft tissue does not fossilize. Soft tissue such as important ligaments are significant in the mechanism of the foot. Ligaments bind our foot bones together as well as the tendons of the foot muscles (Wright). The Hominin foot evolved from being a grasping appendage that was capable of manipulating objects to being a stiff propulsive lever (DeSilva). When life in the trees was more prominent than life on the ground, the foot had a divergent big toe that was used to grasp tree branches when climbing. Today that divergent big toe is no more as it has become adducted, or in line with the other toes. This is mainly because of balance and support of the body as well as enabling easier movement in order to be propelled in the forward direction for walking and running. As found from fossil evidence through Ardipithecus ramidus, it still had a flexible big toe that was divergent. This shows that its ability to walk upright was primitive for this Hominid. Because the toe was still flexible, it demonstrations that it still had the capabilities to grasp either branches to climb trees (Lovejoy), or to manipulate objects. Modern humans have significantly lost the ability to manipulate objects with their feet as it is no longer the foot’s main function. Another change in the foot is the curvature of the phalanges. A modern human’s phalanges are straight, where fossil evidence shows us that Ardipithecus ramidus had slightly curved phalanges which indicates the function of grasping and arboreal locomotion, but still having the ability to move bipedally (Larsen). The discovery of Ardipithecus ramidus is important because it shows a transitional being from life in the trees to life on the ground, and the emergence of bipedal locomotion. The structure of the foot from the arch, flexibility, and the distribution of weight on the foot are all important (Bates). It was modified from a flexible structure with a grasping function for arboreal locomotion, to a rigid structure with a lever function for terrestrial locomotion (D’Aout). According to DeSilva, the central thing for the transition from life in the trees to life on the ground was the development of the longitudinal arch. It “helps store elastic energy and stiffen the foot during bipedal locomotion” (DeSilva). The development of the arch in the foot of the hominid is in coincident with the greater demands placed on the foot as humans began to run (McKeon). The arch in the human foot acts as a shock absorber so damage is not done to it. However it is hard to find direct evidence for arch evolution because the soft tissue does not fossilize. From a biomechanical viewpoint, the foot is typically considered a well-designed unit with two important jobs to do. They are to support the body weight when the organism is standing still, and to function as a lever to propel the body forward in walking and running. Seeing that Ardipithecus ramidus did not possess more similar characteristics to the “efficient” foot, it is generalized that it was not very good at running, and probably stuck to simple walking and climbing in trees. The act of walking upright is a complex process that needs a well-designed foot in order for it to be done efficiently. Walking is considered to be a cyclical process. One starts out with their right foot out and the heel touches the ground. Eventually the foot is fully on the ground with the ball and toes touching as well. While this is happening with the right foot, the left foot is pushing off, propelling the body and then swinging forward in order to repeat the process that just occurred with the right foot. There is evidence of this cyclical process in fossilized footprints found in rock. They call them the Laetoli footprints and they date back to 3.5 million years ago. The walking gaits of the hominids were small suggesting that they had short legs and were short beings. Creatures such as Lucy who was an Australopithecus and was discovered in 1974 in Ethiopia; they were found to be bipeds but very short. When Lucy’s skeleton was assembled, it was found she had flat feet (DeSilva). Eventually as they grew to be naturally taller and larger creatures, the requirement for a stronger foot needed to be developed i.e. the arch, and the flexible lever like propulsion of it. All primates possess a transverse arch, but only humans have a longitudinal arch making non-human primates physically and functionally flat-footed (DeSilva). Apes are flat footed because of their need for grasping. There was another set of footprints discovered in Ileret which is a village in Kenya. These footprints are important because they are the first that showed walking like a modern human. The Ileret Homo erectus footprints show all the fundamentals that we see in our own feet. Aspects such as the double arch which is the long one extending from the heel to the base of the toes and the side to side one were seen as well as the adducted big toe. The Laetoli fossil showed that the big toe was divergent from the other toes. Because the Ileret beings had a foot just like the modern human, it provides proof that they had adapted for activities requiring travel such as hunting and long distance walking (Larsen). The study of the evolution of bipedalism and the morphology of the foot illustrates many evolutionary concepts. To begin with, the development of the human foot has happened over millions of years which coincides with Darwin’s theory of gradualism. Our foot is the result of many years of change that occurred at a very slow rate. The development of the foot also had to be evolutionary advantageous or else it would not have been naturally selected for. Hominids who started walking most likely were able to give themselves and their offspring more resources to better survive because they developed new behaviors from traveling terrestrially such as hunting. The need to run was most likely naturally selected for as well; the stronger more propulsive foot was proven beneficial. Whether it was being able to run away from predators or chase after prey, the ability to run must have been very important because we can see it in the way the foot is designed. It most likely gave the organisms a better chance of survival, in which they were then able to reproduce and pass off their beneficial traits to their offspring. Another concept that this evolutionary adaptation goes along with is that of common descent. Even though it is a controversial topic, scientific research has proven that we have a shared ancestry with apes. The Hominidae include orangutans, gorillas, chimpanzees, bonobos and humans; our most recent ancestor are chimpanzees. This group which includes humans are referred to as the great apes. The divergence between humans and the last common ancestor is now estimated to be eight to ten million years ago. As Francois Jacob wrote, “evolution is a tinker not an engineer”. Evolution did not suddenly produce organisms, organisms emerged from the genetic variation that was present in the already existing gene pool (National Academy of Sciences). Evolution tinkered with the genetic information it already had available and over time new organisms and adaptations emerge from preexisting ones. You can see this with the present day human foot. You have five toes which are all in line with each other. Evolution took what used to be a diverged big toe used for grasping or manipulation and eventually after “tinkering” that toe was better placed when in line with the other toes in order for the organism to walk better. Also, the toes are shorter. The decreased need for grasping objects with the feet over time selected for toes that were not used for that. Keeping in mind though we still possess some flexibility, which is important for the mechanism of walking; you can flex your toes up and down. The hands however are used for the same original purpose, so tinkering with them was not as necessary as they were and are still used today for grasping and manipulation of objects. Also, one can deduce why the need for the foot to evolve to the way it is today by watching someone walk on their hands. It proves to us that the design is not as efficient. You can still walk on your hands and move forward and backward, but supporting your body weight for an extended period of time and balance proves to be more difficult. The origins of bipedalism is a source of great debate. There are many theories as to why it happened but one can only make their own assumptions based on current theories from others, the information presented to them, and how they interpret that given information. Whether it was the search for food, changing climate, or the absence of trees, bipedalism occurred. The development of bipedal locomotion is said to be the most important adaptation in the hominin lineage. It allowed Hominids to travel and move to new places on the Earth. The formation of bipedalism is an evolutionary development that led to how we are as humans today. Fossil evidence has given us insight about our hominid ancestors. Learning about how the foot has developed to what it is today is important to understanding our evolutionary history. Without a specialized tool such as the foot, we would not be able to do things we find to be simple, like walking and running. Walking upright is something that is essentially human; it is one of our defining characteristics. The emergence of bipedal locomotion has made us who were are today and it could not have been done without the foot and the changes that has happened to it.

Koporc.3 (talk) 03:19, 18 November 2014 (UTC)Christine K.