Learning English. I’m Sam.

And I’m Roy. Whether it’s salmon swimming

upriver to lay their eggs or cheetahs running

faster than a car, animals can do incredible

things with their bodies.

Human bodies are no less incredible –

just think of Olympic swimmers and sprinters.

Our bodies work using just the energy

provided by what we eat. This means

that the human body has to be incredibly

efficient, using as little energy as possible

to do what it needs to.

Yet even with our efficient bodies, no-one can

run as fast a cheetah, not even Olympic

champions! In this programme, we’ll be

asking: exactly how efficient

is the human body?

We’ll be comparing human bodies’ performance

against each other, and against some

animals too. And, of course, we’ll be

learning some new and

useful vocabulary as well.

But before that I have a question for you,

Roy. Efficiency involves an input and

an output. It‘s about the relationship

between the amount of energy

coming in – in other words, the food

we eat - and the amount of the energy

going out – the usual movements and

activities of day-to-day life. So,

according to this definition, which

animal is the most efficient? Is it:

a) an ant? b) a whale? or c) a human?

Humans are the most efficient animal.

OK, Roy. I’ll reveal the answer later in the

programme. To find out more about

how the human body works it’s

helpful to know how our species

evolved. Here’s Herman Pontzer, professor

of evolutionary anthropology at

Duke University, speaking with BBC World

Service programme, CrowdScience.

Humans are remarkably efficient.

We walk on two very straight legs, if

a human stands next to a dog, for example,

the dog has got that funny bent classic

dog leg shape, right? And that crouched

posture is really typical of most animals.

Humans have a very straight leg, and so

because of that, and because our legs

are pretty long for our body size – humans

are part of the ape family – we’re are efficient.

Humans are apes and evolved from the

same origin as gorillas and chimpanzees.

One big difference however is that humans

walk upright on straight legs, whereas

most animals are crouched – bent over

at the knee and leaning forwards

to the ground. This crouched posture is not

an efficient way to move.

Other animals, like dogs, have flat backs

and move on four bent legs called

doglegs – something bent in the shape of

a dog’s leg. The word dogleg can also mean

a sharp bend in a road or path.

So, the design of the human body makes it

efficient compared to some other animals - but

how do humans compare with each other?

How do Kenyan athletes break long-distance

running records, while many of us struggle

to run for the bus? The main reason, according to

Loughborough University physiologist,

Rhona Pearce, is training. But there may be

other factors too, as she explained to

BBC World Service’s, CrowdScience.

Age probably comes into it in that there’s

probably an optimal age for tendon

elasticity – that drops off as you get older,

so probably there’s a sweet spot in age for

running economy. So, in terms of weight, it

depends on what you weight is made up of,

if you’ve got more muscle mass that’s going

to help you, whereas if it’s more fat

then you’ve got to carry it.

Efficient running depends on having flexible

muscles and tendons, and this flexibility

drops off, or decreases, as we get older.

This means that, in terms of running, the body

has an optimal age – the best age, or the age

at which you are most likely to succeed.

Body composition also plays a part.

Efficient runners need high muscle mass - the

amount of muscle in your body, as opposed

to fat or bone. So, training, age, muscle mass

and genetics and are all factors which,

when they come together, produce

a sweet spot – the best possible combination

of factors and circumstances. And from the

evidence it looks like my answer to

your question was right, Sam.

Ah yes, I asked which animal was the most

efficient, and you said it was c) a human. Well,

I’m sorry to say but that was the wrong

answer! The funny thing is - and scientists

still don’t understand why - but the bigger

the animal, the less energy it uses,

kilo for kilo. So, the most efficient animal…

…is also be the biggest – a whale! OK, let’s

recap the vocabulary from the programme,

starting with crouched – a position, which

is bent at the knee, leaning forward

and closer to the ground.

A dogleg can describe something which

has a bent shape, especially

a sharp bend in a road or path.

The optimal age to do something

is the best age to do it.

If something drops off, it decreases

in quality or quantity.

A sweet spot is the best possible

combination of factors or circumstances.

And finally, muscle mass is the amount

of muscle in your body, as opposed to fat

or bone. Once again, our six minute are up.

Bye for now!

Bye!