BBC Science The Theory of (nearly) Everything 2019

THE FUNDAMENTALS OF LIFE

“Life is often said to have started spontaneously

in a ‘primordial soup’ – a sort of chemical stock

formed in the pools and puddles of early Earth”

5 old, but little is known about the

organisms that made them.

The oldest evidence of life on Ea r t h

is mysterious traces of a certain

isotope of carbon, which researchers

t hink must have been produced by a

living orga nism. Some of t his g raphite,

also found in Western Australia,

is t hought to have for med a round

4.1 billion years ago. This is almost

as old as the oldest rocks ever found

TRAP

SAMPLING PROBE

COLD

WATER

WATER VAPOUR,

METHANE,

HYDROGEN AND

AMMONIA

ELECTRICAL

SPARK

CONDENSER

COOLED WATER

(CONTAINING ORGANIC

COMPOUNDS)

HEAT

ELECTRODES

DI

RE

CT

IO

N^

OF

W

AT

ER

VA

PO

UR

CI

RC

UL

AT

IO

N

SEAWATER

SAMPLING

PROBE

TO VACUUM

PUMP

Miller introduced

electricity to

simulate a lightning

storm. The process

generated amino

acids – the building

blocks for life.

on Ea r t h, suggesting life may have

appeared surprisingly soon after the

planet formed.

But what left these tantalising traces

of life? Here the trail goes cold. The

t heor y of how life bega n, f rom t he

innate chemistry of early Earth to

those early cells, is a puzzle that

remains unsolved.

Q

Why are there still so many

unanswered questions?

A

As well as there being no clear

evidence to exa mine, at t he hea r t

of the problem is a paradox. To make

the complex biological molecules

required for life normally requires

other biological molecules. How could

any of these intricate molecules be

made when biological systems did not

exist to make them?

DNA, for exa mple, ca nnot for m by

some sor t of chemical accident – to

ma ke it requires specif ic enzy mes. But

to make those enzymes requires the

precise instructions carried by DNA.

There are other fundamental

problems too – even if complex organic

molecules like enzymes and DNA did

arise spontaneously, how and why did

they begin to cooperate as a system?

And how did early life manage to

create large organic molecules without

the complex energy systems that drive

the process in modern cells?

Q

What exactly is a ‘primordial

soup’?

A

Life is of ten said to have sta r ted

spontaneously in a ‘primordial

soup’ – a sort of chemical stock formed

in the pools and puddles of early

Earth. Charles Darwin once wrote

a letter to a friend in which he

speculated whether life could have

originated in “some warm little pond

somewhere” and scientists such as JBS

Haldane and Alexander Oparin (who

coined the phrase ‘primordial soup’)

developed the theory in the 1920s.

Both said that various chemical

compounds could accumulate and

become concent rated in locations

where hydration and drying regularly

occur, such as shorelines, rocky pools

or oceanic vents. Cycles of hydration

and drying, plus energy from magma,

Scientist Stanley Miller combined seawater and various

gases together to replicate the ocean and the atmosphere

THE KEY EXPERIMENT