Man vs beast: Who is more efficient? (Medium)

Hello. This is 6 Minute English from BBC Learning English. Im Sam.

Roy

And Im Roy. Whether its swimming upriver to lay their eggs or cheetahs running faster than a car, animals can do incredible things with bodies.

Sam

Human bodies are no less incredible  � just think of Olympic swimmers and sprinters.

Roy

bodies work using just the energy provided by what we eat. This means that the human body has to incredibly efficient, using as little energy as possible to do what it needs to.

Sam

Yet even our efficient bodies, no-one can run as fast a cheetah, not even Olympic champions! In this programme, well be : exactly how efficient is the human body?

Roy

Well be comparing human bodies’ performance against each other, and some animals too. And, of course, well be learning some new and useful vocabulary as well.

Sam

But that I have a question for you, Roy. Efficiency involves an input and an output. Its about the relationship the amount of energy coming in  � in other words, the food we eat - and the amount of energy going out  � the usual movements and activities of day-to-day life. So, according to this definition, which animal the most efficient? Is it:

a) an ant?

b) a whale? or

c) a human?

Roy

Humans the most efficient animal.

Sam

OK, Roy. Ill reveal the answer later in the programme. To find out about how the human body works its helpful to know how our species evolved. Heres Herman Pontzer, professor of anthropology at Duke University, speaking with BBC World Service programme, CrowdScience.

Prof Herman Pontzer

Humans are remarkably efficient. walk on two very straight legs, if a human stands next to a dog, for example, the dog has that funny bent classic dog leg shape, right? And that crouched posture is really typical of most animals. Humans a very straight leg, and so because of that, and because our legs are pretty long for our body  � humans are part of the ape family  � were are efficient.

Roy

Humans are apes and evolved the same origin as gorillas and chimpanzees. One big difference however is that humans walk upright on straight legs, most animals are crouched  � bent over at the knee and leaning forwards to the ground. This crouched posture not an efficient way to move.

Sam

Other animals, like dogs, have flat backs and move on four legs called doglegs  � something bent in the shape of a dogs leg. The word dogleg can also mean sharp bend in a road or path.

Roy

So, the design of the human body makes it efficient to some other animals - but how do humans compare with each other? How do Kenyan athletes break long-distance records, while many of us struggle to run for the bus? The main reason, according to Loughborough University physiologist, Pearce, is training. But there may be other factors too, as she explained to BBC World Services’, CrowdScience.

Pearce

Age probably comes into it in that theres probably an optimal age for tendon elasticity  � that drops as you get older, so probably theres a sweet spot in age for running economy. So, in terms of , it depends what you weight is made up of, if youve got more muscle mass thats going to help , whereas if its more fat then youve got to carry it.

Sam

Efficient running depends on having flexible and tendons, and this flexibility drops off, or decreases, as we get older. This means that, in terms of , the body has an optimal age  � the best age, or the age at which you are most likely succeed.

Roy

Body composition also plays a part. Efficient runners need high muscle mass - the amount of in your body, as opposed to fat or bone. So, training, age, muscle mass and genetics and are all which, when they come together, produce a sweet spot  � the best possible combination of factors and circumstances. And the evidence it looks like my answer to your question was right, Sam.

Sam

Ah yes, I asked animal was the most efficient, and you said it was c) a human. Well, Im sorry to say but was the wrong answer! The funny thing is - and scientists still dont understand why - but the the animal, the less energy it uses, kilo for kilo. So, the most efficient animal…

Roy

…is also the biggest  � a whale! OK, lets recap the vocabulary from the programme, starting with crouched  � a position is bent at the knee, leaning forward and closer to the ground.

Sam

A dogleg can describe which has a bent shape, especially a sharp bend in a road or path.

Roy

The optimal age do something is the best age to do it.

Sam

If something drops off, it decreases in quality quantity.

Roy

A sweet spot is the best possible combination of factors or circumstances.

Sam

And finally, mass is the amount of muscle in your body, as opposed to fat or bone. Once again our six are up. Bye for now!

Roy

Bye!