LECTURE 1: THE APE THAT COOKS
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Christmas Lectures 2005 – Lecture handouts
The truth about food – Presented by Sir John Krebs, FRS
LECTURE 1:
THE APE THAT COOKS
Broadcast on 26th December 2005
INTRODUCTION
Most of us are just recovering from an enormous seasonal
feast. We tend to take for granted the food we eat and the fact
that we have lots of it. But how did we end up eating fabulous
Christmas meals when our early ancestors scrabbled around for
nuts and seeds? In this lecture John explores the history of
food, from our earliest predecessors, through the great
‘miracles’ which completely changed our diet and the way we
lived, to today’s gourmet extravaganzas. This 3-million-year
journey takes us through the prehistory of our early ancestors,
the rise of civilisation, the spread of human beings across the
planet and ends with the emergence of one of the greatest
science labs of all: the domestic kitchen. There we can
experiment with new ways to use food in our celebrations
together.
FOOD
Welcome to the annual Royal Institution Christmas Lectures.
These lectures on important subjects have been held since
1825, 180 years ago. This year they’re about something
everyone’s talking about: food.
In these lectures I reveal the truth about food. I explore the
myths about it, try to uncover some of its secrets, and separate
out some of the scares from the facts.
Yesterday was Christmas and most of us celebrated it in some
way. The food most of us ate was pretty spectacular. But the
first big truth about food is that almost all the food we eat
today has an amazing story behind it.
In this lecture we start by doing a bit of time travelling. We go
back through time to find out why we eat what we eat.Christmas Lectures 2005 – Lecture handouts
CHRISTMAS DINNER
For many of you Christmas dinner included the traditional
turkey, with potatoes and broccoli and all the rest, followed by
Christmas pudding, mince pies, and some chocolates.
But what would our distant ancestors have eaten? Well, they
would not have celebrated Christmas at all, but if they had,
they couldn’t have eaten this sort of meal. For one thing,
turkeys and potatoes come from North America and were only
introduced to the rest of the world about 500 years ago.
So let’s see what they would have eaten instead.
Four million years ago apes started to walk and the process of
becoming human began. Australopithecus was one of our most
important ancestors who lived in East Africa 3 million years ago.
His little pre-human body is similar in some ways to ours. Let’s
look for clues about what he ate in his teeth and his jaws.
TEETH
You can tell a lot about different animals by looking at their
teeth and jaws. The elephant’s teeth are very large, broad and
flat – ideal for grinding up tough grass, bark and leaves. Lion’s
teeth however are quite different. They’re smaller and also a
different shape – sharp ridges on the teeth are perfect for
cutting and tearing through flesh.
What about Australopithecus’ teeth? His teeth are much smaller,
but also, their shapes are all somewhere in between those of
the lion and the elephant. The front teeth (incisors) are similar
shapes to a lion’s but they are nowhere near as well developed
for tearing flesh. The back teeth (molars) would be good for
grinding things. But again, nowhere near as effective as an
elephant’s. So Australopithecus didn’t specialise in one type of
diet – he ate a bit of everything. In that respect his teeth were
a little like our own, because we eat a bit of everything too.
But there was a big difference between Australopithecus and
us. If you compare his teeth with yours, you can see they are
similar sorts of shapes, but they’re much larger. And so is his
jaw. In fact, his jaw is huge compared with yours.
The jaw muscles of Australopithecus wrapped all the way up to
the top of his head where they were attached to a big ridge
running front to back along his skull. Your skull doesn’t have
this ridge because your jaw muscles are much less powerful.
The reason why Australopithecus had such a big jaw and huge
teeth was that he must have chewed much tougher food than
we eat today – in fact, some things we’d find impossible to
chew, like inedible hard nuts and seeds. Not very appetising, isChristmas Lectures 2005 – Lecture handouts
it? A few nuts, seeds, roots, and fruits, a little raw meat – and
wriggling insects as a delicacy!
How did we get from eating this collection of hard nuts and
seeds to spending hours basting a turkey?
Two million years ago, our ancestors begin to change. It’s a
gradual process. Fossil skulls from that time are much more
like ours. A smaller jaw can no longer crack open the big,
heavy-duty nuts. So our diet must have slowly changed so that
our jaws changed through evolution in this way.
And around the same time as our jaws were getting smaller,
our brains were increasing in size. One explanation might be
that we began to eat a lot more meat to feed our ever-
enlarging brain.
But at some point about 300,000–400,000 years ago, our diet
changed dramatically. One day, and no one is quite sure when,
one of our ancestors came up with one of the cleverest ideas
of all time. It’s a process involving food that makes us
absolutely unique in the animal kingdom and would change
our diet forever. And it probably started with a storm.
Can you guess what it was?
FIRE
Lightning can start a fire! And in nature, lightning starts forest
fires all the time. What’s that got to do with our food? Well, it’s
likely that our ancestors would have picked up some charred
seeds or meat after a forest fire, and found that not only was it
easier to eat, it was also very tasty. As a species we absolutely
love the taste of cooked foods.
But waiting for lightning to strike and create a fire is too
unpredictable. And keeping the fire going after a storm is hard
work. Eventually someone worked out that it’s much better to
make fire yourself … but how did our ancestors manage it? One
possible way was by rubbing sticks together. The idea is that
by rubbing bits of wood together, the friction heats them up
enough that they start to smoulder, and then you can set fire
to bits of straw.
So it’s hard work and difficult to make a fire – is it really worth
all the effort? The answer is yes – the ability to cook makes an
enormous difference to food. And not just to the taste.Christmas Lectures 2005 – Lecture handouts
COOKING – THE HUGE BENEFITS
Take a lump of raw meat: fatty, solid, hard to chew, and hard
to digest. Cooking transforms it. But it’s not just the look and
feel of food that changes when you cook. For example, kidney
beans cannot be eaten unless cooked because they contain a
poison that you have to boil out of them. Cooking food
properly also kills bacteria that might give you food poisoning.
And it’s a chemical magic that turns the utterly inedible into
the completely delicious. Inedible uncooked popcorn would not
kill you … but it wouldn’t exactly be pleasant to eat.
Dried maize seeds are hard, brittle and almost completely
indigestible – if you tried to eat them you might break your
teeth. But something amazing happens inside these maize
seeds during the minute or two it takes to cook them. The
maize seeds have a very tough outside coat. The insides are
packed with starch granules and a small amount of water. As
the seeds are heated, the water changes into steam and
expands. With the seed’s tough coat, however, there’s nowhere
for the water to expand to. So it gets hotter and hotter and
hotter, and the pressure inside the seed builds and builds and
builds. Then, at around 175 Celsius the pressure inside reaches
nine times normal air pressure, and at that exact point the
shell breaks.
We have popcorn!
As the corn explodes, the hot starch granules expand very
quickly and dry out as the superheated steam escapes. That’s
how you get the fluffy white popcorn. Cooking has changed the
seeds from horrible to delicious, but it’s also changed from
inedible to something your body can digest as food.
Cooking must have struck our ancestors as a kind of miracle.
(Popcorn isn’t a new invention by the way. Archaeologists have
found evidence which suggests early Mexicans were doing it at
least 80,000 years ago.)
COOKING – POSSIBLE EVOLUTIONARY
BENEFITS
Whilst Australopithecus crushed seeds like maize kernels with
her strong jaws and teeth, we humans turn it into food by
cooking it. Cooked food is much easier to chew, and it’s more
efficient for our stomachs to digest and absorb. When starchy
foods like soybeans, potatoes and cassava are cooked, they offer
almost twice as much digestible energy as they do when raw.
That is great news if you have not got quite enough to eat in
the first place.Christmas Lectures 2005 – Lecture handouts
Cooking gave early humans a huge advantage over our
competitors. And to this day we are still the only animal to
cook its food.
But those big brains of ours just kept coming up with smart
ideas. It took a little time, though in the scheme of things it
was almost yesterday. The next great invention that
transformed food was only a mere sliver of time away from
today – just 10,000 years ago. And this invention changed us,
and the entire world, beyond recognition.
To find out what was invented and why, we must go back to
just before this great invention happened – 10,000 years ago.
THE HUNTER-GATHERER
In those days, humans relied on two ways to get food. One
was literally to find it, picking up bits and bobs like seeds and
fruit as we wandered about. To get enough to eat, humans had
to forage like this almost all the time. You couldn’t stop, even
to deliver a lecture. And when foraging for food got really
boring, as it must have done, people went hunting.
However, there was a drawback: hunting is not easy, and
10,000 years ago it was a pretty dangerous activity. Tribes in
South America and Africa, that still live as hunter-gatherers
today, spend up to seven hours each day just finding food, so
the second great miracle that transformed our diet had massive
appeal.
Have you guessed what it was yet?
FARMING – FROM PLANT FARMER …
Farming may have started when hunter-gatherers, living in small
groups, dropped some edible seeds near where they lived.
These grew into plants.
Or maybe the indigestible seeds inside fruit they ate passed
through their bodies and came out neatly packaged with a
dollop of fertiliser, and those seeds grew into shrubs or trees.
After this, deliberately planting the seeds wasn’t such a big
step. But it was a hugely significant one … that changed the
fortunes of the human race entirely.
The second great invention, farming, allows you to make food
of your own: you don’t have to wander about finding it or
chasing after it through the forest. The consequences were
astonishing. Farming allowed the population to grow, and to
keep growing at an ever-increasing rate.
But farming also caused something else. Plants have to be
tended and harvested to get the best out of them. And so veryChristmas Lectures 2005 – Lecture handouts
soon the wandering hunter-gatherers decided to stay put and
watch their plants grow. Settlements became villages. Villages
became cities. And in these cities, because farming was so
efficient, not everybody had to be out looking for food all the
time. So people were able to do other things. Food – and the
farming of it – gave us civilisation.
Farming also gave us early science.
FARMING … TO BREAD
The first farmers were the first scientists.
Imagine you are an early farmer and you’re farming grass
plants, the ancestors of wheat. They have been growing around
the hut where you’re living. You notice that some of the plants
produce more seeds for you to eat than others. You then have
to choose which plants you’re going to take seeds from to
grow next year’s crop.
You’d pick the plants with the most seeds – of course you
would – because you want each new plant to grow as much
food as possible – you want the biggest yield from your crop.
When the next year’s crop is ready, most of the new generation
of plants have grown more seeds. The number of seeds grown
in this grass is genetically determined. So the new generation
has inherited the tendency to grow more seeds.
Which plant would you choose to breed from this generation?
The one with the most seeds again, of course. By the time you
have selected a fourth generation of plants, the yield of your
crop has increased dramatically, because the trait you’ve been
selecting for is passed on from one generation to the next, in
the plants’ genes.
So early farmers were our first geneticists. Over thousands of
years, farmers chose again and again, in every season, the
biggest, plumpest looking plants, and they discarded the types
of plant they didn’t want. The effects, in a very short time
were, startling.
With wheat, for example, they selected for size. Wheat started
as a form of grass in, it is thought, the mountains of Anatolia,
now part of Turkey.
The wheat grains that the ancient Egyptians grew were about
very short. But modern wheat grains, produced from years of
selective breeding, are much, much longer and give us a lot
more food in each grain, for the same effort.
The same thing happened across the world with the different
staple foods. They selected plants mostly for size and
healthiness.Christmas Lectures 2005 – Lecture handouts
Farming meant that more people than ever before had food in
their bellies. For the first time people had the means to
produce enough food, without everyone spending every waking
hour finding it. So what happened then? With food, and free
time, it was time to enjoy food.
ROME – THE FEAST
We’ve all been brought up on stories of the incredible
extravagance of the Romans, of immense feasts that lasted for
days. But the truth is that the great feasts of legend were only
for the very rich. And even those were surprisingly simple.
There’d be lots on offer, but it mainly consisted of chunks of
meat and poultry and various sorts of stews and pies.
Most Romans, like everybody else who was supported by early
farming, ate an incredibly simple diet. That’s because farming
gave them staple foodstuffs like wheat and milk but it didn’t
give them variety, or excitement, or pleasure.
For that, we need the third great miracle of food – processing.
Processing food, applying science and technology to the way
food is prepared, produces new and extraordinary foodstuffs
for us all to enjoy. And that is what leads, eventually, to the
sort of meals we now all take for granted – including, of
course, yesterday’s Christmas feast.
PROCESSED FOOD
Most farmed food was based on a few staples. So ancient
peoples kept trying to think of ways to make them more
interesting. The Egyptians, for example, took wheat and turned
it into bread. Five thousand years ago the Chinese took rice
and turned it into noodles. And the Romans used lots of
sauces. They added garum (fermented, crushed anchovies) to
improve its flavour! Of course, we’ve moved on since the
Romans, and now enjoy a much wider range of flavours than
‘fish sauce on everything’!
All these inventions were an early form of processing food:
using technology to turn boring raw ingredients into something
more interesting or useful.
But it wasn’t until the modern age that the idea of processing
food would really take off. When it did, it would allow
everyone, not just the privileged elite, to eat wonderful, varied
and interesting food. And that brings us to one of the most
delicious foods of all time – chocolate.Christmas Lectures 2005 – Lecture handouts
CHOCOLATE – HISTORY
The miracle of chocolate is that it has such an unpromising
start. It is made from cocoa beans, which, take it from me, are
squishy, bitter, and taste more like bad fruit than chocolate.
You really wouldn’t want to eat them!
All the things we love about chocolate are things we have
added to this unpleasant bean. The bean itself, horrid as it is,
was eaten in South America from at least 1000 years ago. How
do you process this to make it nice to eat?
About 600 years ago the Aztecs discovered that they could
ferment and then roast the beans, then grind them up, add hot
water, and make a drink. The result is a kind of hot chocolate.
It’s pretty fatty and quite disgusting, nothing at all like the hot
chocolate we know now.
Well, the Aztecs then added vanilla to make it creamier, and
sugar to counter the bitter taste. It’s not much better, but even
this early processing made the cocoa bean more useful and
interesting than it was.
Once chocolate was brought to Europe a series of discoveries
were made about it. A whole new set of elaborate processes
finally unleashed the full potential of the humble cocoa bean.
Europeans found the Aztecs’ drink too greasy. So one of the
first things they did was transform it by squeezing the fat,
called ‘cocoa butter’, out of the ground beans before they
made them into a drink.
This cocoa butter floated on top of the Aztecs’ drink. Without
the fat the drink became smoother and much more delicious. It
was the modern hot chocolate we still enjoy today.
CHOCOLATE – INDUSTRIAL PROCESSING
Hot chocolate was wonderful, and it still is. But people liked
the taste of chocolate so much they wanted to be able to carry
it around with them. And it’s hard to do that with a hot liquid!
A breakthrough came with another process. This involved
heating a chocolate mixture from the ground-up cocoa beans,
and then adding back in some of the cocoa butter, and carefully
controlling the cooling process. As it cools the mixture sets.
The result was chocolate bars.
To get chocolate the way we want it involves a series of
processes, which have to be absolutely exact at every stage.
One of the things you have to get absolutely right is the
cooling from a liquid to a solid. When it stops moving as a
liquid, the fat molecules stop flowing over each other and the
mixture sets, with the fat molecules in a lattice pattern.Christmas Lectures 2005 – Lecture handouts
The arrangement of that lattice is what determines the
properties of the chocolate.
Different binding patterns result in different properties of the
chocolate.
Cooling the mixture very slowly and carefully, while stirring,
allows the cocoa butter to crystallise the right way. That
process will give the set chocolate the combination of the
glossy surface, brittleness, melting point and smooth texture
that we love.
But if we cool the molten chocolate very fast with liquid
nitrogen the fat molecules don’t form the right structure. This
chocolate’s not shiny and will not melt in your mouth.
Today we process chocolate on a massive scale. In Britain, we
produce almost 1500 tonnes of chocolate every day. That’s the
same weight as 100 double-decker buses.
CHOCOLATE – TECHNOLOGICAL MASTERY
Today, processed chocolate is a triumph of science and
engineering. And it has some remarkable properties. You can
use some of those properties to make chocolate unlike
anything you’ve seen before – you can even tie it in a knot.
We think of chocolate as being a solid at room temperature,
and melting in your mouth. But it’s more subtle than that.
Chocolate is cocoa butter with sugar and cocoa solids
dispersed through it. At room temperature, most of the cocoa
butter is in a rigid lattice, and the chocolate is solid. But we
can manipulate that structure.
The usual way of doing that is to heat the chocolate up – but
then it just melts, and you get hot chocolate again. What you
can do instead is apply pressure to the chocolate. That
disrupts the lattice – the areas of liquid fat join together, which
then allows the solid areas to slide across each other. The
chocolate starts to behave more like a liquid. It does not heat
up, but it does start to flow.
We can put some ordinary solid chocolate in a hydraulic ram
and put it under pressure. The chocolate is extruded through
the nozzle, and you can even tie it in knots. The extruded
chocolate stays flexible for a few minutes, even hours, until the
fat re-crystallises into its original matrix. At that point, the
chocolate becomes brittle again, as you might expect.Christmas Lectures 2005 – Lecture handouts
SUMMARY
So we started off with a revolting, almost inedible cocoa bean
– perhaps the sort of thing our friend Australopithecus might
have had to eat, but not something we can enjoy. Today we
farm the beans on a massive scale, we collect and roast them,
we apply a huge amount of science, and we pass the beans
through vast industrial processes using extraordinary
techniques. And we create not just food, but pleasure.
And pleasure not for a small, rich elite, but by the tonne.
But why do we love the foods that we do? What is it that
makes some kinds of food enjoyable, and other kinds seem
disgusting?
In the next lecture, Yuck or Yummy, we explore how our
individual backgrounds and cultures affect the sorts of foods
we like, and those we hate.
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