Hello. This is 6 Minute English from BBC
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!