and

we really started with an observation a that humans are amazingly good products and we

can throw both with incredible accuracy and complexity

and people would notice for years that humans are amazing errors if you look at

any professional baseball player cricket all they can throw ninety two hundred miles an hour

many times over and over again single came but really i think the most amazing

thing is what normal class so if you look at any

a little league baseball game in any town american you could find a twelve or

thirteen year old kid a control sixty or seventy miles per hour and that to

me is really remarkable performance that ability comes in to better focus when you consider

what chimpanzees for our closest a living relatives can do in terms of performance and

user really athletic

the very strongly hundred how they can run essentially right up the tree but adult

males don't throw about twenty miles row

which is about thirty as fast as the not twelve or thirteen why is it

and how is the humans are so good when to that occur most of occur

sometime during a revolution that we can control

and probably arguably most important why

what we started to look at was the mechanics of how someone throws an object

held really remarkable thing that humans do is the store energy in their shoulders i

and it sort of good analogy for how that storage occurs a slingshot so with

a slingshot you full really heart on those elastic bands that store energy in that

slingshot you're doing the same thing to show

when you're actually throwing your rotating your shoulder back and here you're essentially stretching the

elastic bands that are your tendons and ligaments shoulder

i know store energy and then just like a slingshot when you release

perhaps slingshot that the last energies are then it allows you are real

accelerate an object such as rock for the same things happening we study that in

collegiate baseball we had in our lab and we stuck reflective markers on their arms

and their torso and we recorded how they move in three dimensions what shall see

is that as the army sort of rotated back

that's what we think the last gonna just being stored and then the arm is

rapidly rotating for a number of changes that have occurred during a revolutionary asked to

the shoulder in the or and the torso really make this elastic energy storage possible

and those changes occur at around two million years ago we see hunting behavior merge

around that time

the earliest evidence of hunting in terms of problems or what you're

i think that nature appear around two main years ago synchronous with this behavior we

think that throngs probably most important early on in terms of hunting behavior enabling our

ancestors to effectively

she'll be game and

get more calories that i

and why is that important wise what is wanting matter hunting probably matters because more

calories in your diet means you can build bigger bodies in figure three and have

more bits

the things that matter for evolution the interesting thing about the way that we threw

in the past versus the way to be thrown out

is that there are very few people to throw to hunt and most electable throw

two days during sports

a and the remarkable thing about sports is that you're throwing using this incredible ability

but you're doing it hundreds of times a couple of our snack

wasn't the case

a for how we would've probably

one revolving in use instant

so this remarkable ability which we were able to do doesn't really sync up with

a moderate usage

and what happens is the people actually injure their shoulders and into their l so

at the end of the david the ability that we have just or elastic energy

and shoulder makes us greater hours but it's also injuring is there a number of

things we're doing to follow this research up of one of the things we're doing

is actually looking at what really project house actually work so we know that throwing

probably evolved around two million years ago at least have to differ from what we

don't see evidence of projectiles in the archaeological record for about a million half years

so what was it that we were strong and how is if that were killing

a these animals one way that we can try to look at that is to

look at one capacity of things such as sharpened wooden spears right

what happens if you try to kill something they just the sharpened wooden stick i

can you do it how much energy is required can individuals actually through all these

things effectively and use them time and that's were looking at next