Lecture 10 - Professor Pickering PDF

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Professor Pickering...

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Lect 10 Friday, April 23, 2021

1:21 PM

- Take a more nuance look at how to get into trees via climbing. - Ape-man were great climbers, let's investigate that. A matter of ongoing debate.

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- Taung child skull. Comes from a place called Taung. When this individual died was between 3-4 years old. Belongs to the Australopithecus africanus. - This was the first early homin fossil found in africa, by Raymond Dart. Found in 1994 and announced in 1995. Huge impact on the field of human evolutionary studies bc it was found in Africa. - Dart argued it wasn't some Ape, but a direct ancestor of ourselves. - The reason that Dart inferred that this was a human ancestor was that it was a bipedal organism. Would have been an obligate biped. Can recall that in an early lecture, this habitual bipedal nature that we display is distinct to humans. Dart argued that we can infer this by bipedal and our upright posture. - You may rightly be asking, how could dark infer this from the fossil. When we talk about bipedalism we talk about legs moving, not heads.

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- He was looking at the frenum magnum. The big hole, entry point for spinal point to connect to the brain. So in other wards spinal cord enters the brain case via the frenum magnum. - The position is different to bipedal vs. Quad pedal. - Lower left hand corner, human skull. Chimpanzee in the bottom right hand image. - Human sits directly, which means if you look directly above, it's position is front of head and in the middle. Chimpanzees is in the back of the skull , skull essentially hangs off. Quadrupeds are more horizontal vs. vertical like humans. - Post crenial bones were found, meaning bones found BELOW the head.

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- That reinforce this pattern was that order called postcranial bones of these various species were found is well and post cranial bones just refers to bones below the head so you can see here is a very early hello that so you can see here is a very early postcranial pittacus africanas the same species that the tongue child belongs to in which represente here is a partial vertebral column start Scott upper right hand corner and moves down towards the sacrum which is the the base of the bracchi will come in, you can see the hi bones a fancy name of which are the endowments and then on the right side of the image but the left side the the fossil you can see the thigh bone the left 5 on there which has a fancy name called the femur what's great about this is that the hip bones in the femur in the backbone or the retiro column of a bipul primate are constructed different than those other quadrupedal priming because muscles drive bones. - The way they move so the way in which you move is gonna dictate the structure of the musculature and that musculature it shaved is gonna dictate the way in which it fits on t bones in mooses bones in there for animals engage in different locomotor behaviors have different not different types of bones but different structure to those same types o bones

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bones - Chimpanzees also has a vertebrae and sacra and femra are they gonna be shaped differently because that animal moves quadrupedal versus bipedally in a human and we understand the way in which those shapes are related to locomotion from the study of modern animals in we can take that knowledge and applied to fossils of unknown locomotor adaptation but interpretations based on their similarities to either bipedal skeletal forms or quadrupedal skeletal forms - So what all this did was reinforce the notion that early human ancestors just like ourselves were essentially fully adapted obligate bipeds from a very early stage and the study of human evolution. - The situation is only exacerbated in 1974 with discovery of the Lucy Skelton. - And additional fossils of her species Australopithecus Afarensis - So like africanus which we just talked about with the taung child Afarensis is one of thes early Ape man's species then I mentioned in the human evolution lectures. - Then I mentioned in the human evolution lectures but is geologically older than africanas, it dates back to about 3.7 or 3.6 million years ago until about 2.9 Ma. - When first discovered in 1774 By danjo hansen, it was the earliest known hominin. - Important about Lucy besides its great age was that new parts of the skeleton were sampled. - We had pieces of the foot and angle and those particular body parts were very similar to structure in modern humans. - That led a lot of people to definitively reject any amount of Arboreal behavior or possibility or that behavior in any early hominin. - Human like ankle and foot, up to 2 Ma. Also human like bipedal that were more recent in time. Solidified that early hominins weren't doing much in trees. - Problem was that this conclusion rests on the assumption that modern humans don’t climb trees and if they do they do it very poorly, that they're incompetent. - Thus by extension, if an early hominin shows human like morphology, like the foot and ankle, it was similarly incompetent as are modern humans. - Basis of the argument that is still ongoing. The assumption is that modern humans are poor climbers, there we can look at their morphology and see what their feet, ankles, foot and how that relates to local motor adaptation. - If we see those same features in a fossil homini they will be similarly adapted as are modern humans ie a poor climber and commited bidped.

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- When you look at the behaviors of living modern extant people, it shows this logic to be flawed.

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- The upshot is that people climb, and they climb well and frequently. - Climbing stairs, trees. - When you look at ppl who live in more traditional, ancestorial lifestyle, (modern hunter gathers, etc) they climb more frequently than modern western people. They still climb a adults, especially if they're men. - Children don't climb as high as young adult males or as dangerous. - Bc we are an animal that has adapted bipedally, why do we still climb as a regular part o the daily routine if it’s a dangerous proposition? We'd predict that the answer must be a fitness adaptive behavior. For the most part, they climb is to acquire edible resources that is available in trees.

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- Primary food that they climb for is HONEY. - Honey is very important to traditional ppl bc it is PACKED with energy. A very energy dense food. 95% Carbohydrates. Mostly carbohydrates. In addition it provides a variety of proteins, essential enzymes, essential minerals, trace elements that are important to human health, and variety of vitamins. - Associated with Larvae, young bees that are in the comb. They are loaded with protein and fat and vitamin B. - Honey is important especially to hunter gathers and foragers. - Haza man, lives in grassland environment. Savanah mosiac environment, more open the what a rainforest is. - Haza value honey as well as a editble resource. - Rainforest it is very valued bc in rainforest Carbohydrate foods are really rare. It's a reliable source. - Even for the Haza honey accounts for the 8-16% of their total colleted calories. - For ppl like the achea, it accounts for up to 22% of their calorie intake. - You have to go into trees for this. - Humans climb trees for fruits. Has sugars and good erngery source.

- Would also climb trees to hunt. - Groups of African foragers, would climb trees and use as shooting platforms. Efficient way to hunt. Is called AMBUSH HUNTING. To use this type of hunting you have to climb.

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- Trees are a good source of protection. - If a herd of elephant come charging through a rainforest village, people scurry up trees t get out of the way. - We can see this general human instinct from our ancestors. - Elaborating in some parts of south east Asia where ppl contract these high and enormou treehouses. Protect from other humans that might want to make trouble for them. - Refection of a Darwinian drive to protect your fitness.

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- There are potential devastating and final consequences for climbing into trees without the assistance of technology. - The way hunter gathers climb, daily. Part of the daily routine for you. Along with it come the fact that you can fall from trees. At the heights that they climb, you could be COMPLETELY removed from the gene pool. - A group that climbs daily mainly to harvest honey, rainforest hunter gathers Faefe who live in central Africa. Climb 19-30 meters to harvest honey. - Sometimes as high as 60 meters to meet their needs and needs of their family. - Think from the perspective of cost benefit analysis. Collected by those who were worrie about safety. - If you fall from 12 meters, you have 45% chance of dying. - 15 meters your chances of dying is 56%. - 19meters - 78% - 19 meters and up+ a chance of 100% that you WILL die. - Chimpanzees are across Africa and live in different habitats. Chimps that live in the west of Africa spend 50% of time in trees that are above 20 meters and 50% below 20 meters - Chimps in Eastern portion of the range. They spend almost all their time below 20 meters. - In gorillas lots of them spend time in trees under 7 meters in height. - Humans are regularly engaging in dangerous activities, tells you abt honey and other resources that grow in trees. - Takes phycology to turn off that fear of climbing trees. Have to gera yourself up for this day in and out. Families wellbeing depends on this. Very important point. Raw physicalogy. Have to be fit. - Compartive approach. - Apes and humans are built differently obvi. - When we think about climbing in particular, Apes shoulders, arms and hands are essential. - But let's talk about FEET. In relevance to climbing, APES have much great abilities in feet than humans. - Relative flexibility, Apes have far more flexibility. Humans don't. Humans mid -food stability is highly adaptive for bipedal walking. In particular for the push off phase. - Flexable feet of apes combined with shoulders, hands, etc allows them to surpass humans in arboriatl perforance like climbing speed, time spent in trees, distance covered in trees. - Apes would win in trees in every case.

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MIDTARSAL BREAK - Tarsal refers to ankle bone. Mid means mid of that massive bone. - Left side is the gorilla and the right is a human. - Calf ascnese from the heel. - Can see where the archilleas tendon is. - If you look at the human you can see the human is toeing off. Up on its toes. Can see this prominent arch. Arches are important for humans in bipedal walking. See the difference in anatoly in the foot. - Gorilla has a upwards bent in it's foot. Characteristic of all apes is called Midtarsal break. SO that it can mold their foot around the trunk. Can plaster their foot to the tree.

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- Can see the Grasping Hallux. Hallux is a fancy word for big toe, great toe. - Imagine that it’s a big advantage in climbing, to grasp the branch with ones foot and not only hand. - Important part to make is that it's not that we don't see evidence of these features in modern humans and or fossil hominins.

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- We can see the humans footprint. They are massively different. - On the left is someone toeing off, in a typical human arch. - We can see that in the footprint. - ON the right we see that the human is toeing off in the mid-foot of the human. Midtarsa breaks may occur in 1 of every 13-15 people. Not as unusual as previously thought in paleoethology. Pretty not uncommon. A-typical feature to see in modern humans - Associated with high body mass index humans. Shoe wearing hypothesis. This is not the normal. The normal is the arch. - Not every human has this feature, but all apes have this feature. - 3.4 Ma partial foot of an early homin from Burtele. Notice that it has a divergent helix (big toe). Telling us that some of our ancestral homins have divergent big toes. - Ardepicthus has a divergent big toe. - Austropethesis afarensis(Lucy) doesn't have a divergent big toe.

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- Third feature that makes Apes extraordinarily climbers is Dorsiflexion, bringing toes up t shin. Chimps have a 45 degree dorsifelxtion. IN a comparative context, when humans walk they only dorsiflex 15-20 degrees and you see ankles injured when you exceed 45 degrees. - Chimps dorsiflex to an extent that would injure a modern human walking around. - Habitual climbers in Africa when they climb, they are able to dorsi flex between 35 - 47 degrees. Which is chimpanzee level dorsiflexion. - Midtarso break and grasping helix is that your able to see those features, able to see those abilities. Those are reflected also in their skeletons that we can pick up in fossil records. - For Dorsiflexion when we look at the bones, there is no fossil indication of that ability.

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muscles, they have different muscle architecture than non-climbing ppl. - When you look at foragers vs. nearby neighbors the structure of their calf muscles, fibe

of them are much longer in the people who are regularly climbing trees. Is not reflected in the bones, but it is in the soft tissues.

- To the fossil record if we find feet of ancient hominin ancestors. - If confronted by the two feet on the slide. On the left is a more recent foot. Gonna conclude that the two separate hominin individuals who own the feet were completely different. - Brotele has a divergent big two. Only line up in a way that makes it divergent. - The recent one doesn't have a divergent big toe, and we can see that by how it lines up. - The Brotele foot would say that it was engaged in arboritial behaviors and was probs efficient. - If you looked at the left one, you would say it doesn’t have divergent big toe so it probably wasn't good at climbing in tree. But we aren't able to see it's muscles bc it may have been good at climbing.

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