| 0:00:04 | and |
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| 0:00:08 | we really started with an observation a that humans are amazingly good products and we |
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| 0:00:15 | can throw both with incredible accuracy and complexity |
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| 0:00:18 | and people would notice for years that humans are amazing errors if you look at |
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| 0:00:21 | any professional baseball player cricket all they can throw ninety two hundred miles an hour |
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| 0:00:25 | many times over and over again single came but really i think the most amazing |
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| 0:00:30 | thing is what normal class so if you look at any |
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| 0:00:34 | a little league baseball game in any town american you could find a twelve or |
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| 0:00:38 | thirteen year old kid a control sixty or seventy miles per hour and that to |
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| 0:00:42 | me is really remarkable performance that ability comes in to better focus when you consider |
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| 0:00:46 | what chimpanzees for our closest a living relatives can do in terms of performance and |
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| 0:00:52 | user really athletic |
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| 0:00:53 | the very strongly hundred how they can run essentially right up the tree but adult |
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| 0:00:58 | males don't throw about twenty miles row |
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| 0:01:00 | which is about thirty as fast as the not twelve or thirteen why is it |
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| 0:01:04 | and how is the humans are so good when to that occur most of occur |
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| 0:01:08 | sometime during a revolution that we can control |
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| 0:01:11 | and probably arguably most important why |
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| 0:01:14 | what we started to look at was the mechanics of how someone throws an object |
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| 0:01:18 | held really remarkable thing that humans do is the store energy in their shoulders i |
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| 0:01:22 | and it sort of good analogy for how that storage occurs a slingshot so with |
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| 0:01:26 | a slingshot you full really heart on those elastic bands that store energy in that |
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| 0:01:31 | slingshot you're doing the same thing to show |
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| 0:01:34 | when you're actually throwing your rotating your shoulder back and here you're essentially stretching the |
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| 0:01:39 | elastic bands that are your tendons and ligaments shoulder |
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| 0:01:43 | i know store energy and then just like a slingshot when you release |
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| 0:01:47 | perhaps slingshot that the last energies are then it allows you are real |
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| 0:01:52 | accelerate an object such as rock for the same things happening we study that in |
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| 0:01:57 | collegiate baseball we had in our lab and we stuck reflective markers on their arms |
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| 0:02:03 | and their torso and we recorded how they move in three dimensions what shall see |
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| 0:02:07 | is that as the army sort of rotated back |
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| 0:02:09 | that's what we think the last gonna just being stored and then the arm is |
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| 0:02:12 | rapidly rotating for a number of changes that have occurred during a revolutionary asked to |
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| 0:02:17 | the shoulder in the or and the torso really make this elastic energy storage possible |
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| 0:02:22 | and those changes occur at around two million years ago we see hunting behavior merge |
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| 0:02:27 | around that time |
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| 0:02:29 | the earliest evidence of hunting in terms of problems or what you're |
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| 0:02:32 | i think that nature appear around two main years ago synchronous with this behavior we |
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| 0:02:37 | think that throngs probably most important early on in terms of hunting behavior enabling our |
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| 0:02:42 | ancestors to effectively |
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| 0:02:44 | she'll be game and |
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| 0:02:45 | get more calories that i |
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| 0:02:47 | and why is that important wise what is wanting matter hunting probably matters because more |
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| 0:02:52 | calories in your diet means you can build bigger bodies in figure three and have |
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| 0:02:56 | more bits |
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| 0:02:57 | the things that matter for evolution the interesting thing about the way that we threw |
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| 0:03:01 | in the past versus the way to be thrown out |
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| 0:03:03 | is that there are very few people to throw to hunt and most electable throw |
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| 0:03:07 | two days during sports |
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| 0:03:09 | a and the remarkable thing about sports is that you're throwing using this incredible ability |
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| 0:03:13 | but you're doing it hundreds of times a couple of our snack |
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| 0:03:16 | wasn't the case |
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| 0:03:17 | a for how we would've probably |
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| 0:03:19 | one revolving in use instant |
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| 0:03:22 | so this remarkable ability which we were able to do doesn't really sync up with |
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| 0:03:26 | a moderate usage |
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| 0:03:27 | and what happens is the people actually injure their shoulders and into their l so |
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| 0:03:31 | at the end of the david the ability that we have just or elastic energy |
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| 0:03:34 | and shoulder makes us greater hours but it's also injuring is there a number of |
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| 0:03:39 | things we're doing to follow this research up of one of the things we're doing |
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| 0:03:41 | is actually looking at what really project house actually work so we know that throwing |
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| 0:03:46 | probably evolved around two million years ago at least have to differ from what we |
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| 0:03:50 | don't see evidence of projectiles in the archaeological record for about a million half years |
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| 0:03:55 | so what was it that we were strong and how is if that were killing |
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| 0:03:57 | a these animals one way that we can try to look at that is to |
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| 0:04:01 | look at one capacity of things such as sharpened wooden spears right |
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| 0:04:05 | what happens if you try to kill something they just the sharpened wooden stick i |
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| 0:04:09 | can you do it how much energy is required can individuals actually through all these |
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| 0:04:14 | things effectively and use them time and that's were looking at next |
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