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[Illustration]


KEEP OUT

BY FREDERIC BROWN


    _With no more room left on Earth, and with Mars hanging up there
    empty of life, somebody hit on the plan of starting a colony on the
    Red Planet. It meant changing the habits and physical structure of
    the immigrants, but that worked out fine. In fact, every possible
    factor was covered--except one of the flaws of human nature...._


Daptine is the secret of it. Adaptine, they called it first; then it got
shortened to daptine. It let us adapt.

They explained it all to us when we were ten years old; I guess they
thought we were too young to understand before then, although we knew a
lot of it already. They told us just after we landed on Mars.

"You're _home_, children," the Head Teacher told us after we had gone
into the glassite dome they'd built for us there. And he told us there'd
be a special lecture for us that evening, an important one that we
must all attend.

And that evening he told us the whole story and the whys and wherefores.
He stood up before us. He had to wear a heated space suit and helmet, of
course, because the temperature in the dome was comfortable for us but
already freezing cold for him and the air was already too thin for him
to breathe. His voice came to us by radio from inside his helmet.

"Children," he said, "you are home. This is Mars, the planet on which
you will spend the rest of your lives. You are Martians, the first
Martians. You have lived five years on Earth and another five in space.
Now you will spend ten years, until you are adults, in this dome,
although toward the end of that time you will be allowed to spend
increasingly long periods outdoors.

"Then you will go forth and make your own homes, live your own lives, as
Martians. You will intermarry and your children will breed true. They
too will be Martians.

"It is time you were told the history of this great experiment of which
each of you is a part."

Then he told us.

Man, he said, had first reached Mars in 1985. It had been uninhabited by
intelligent life (there is plenty of plant life and a few varieties of
non-flying insects) and he had found it by terrestrial standards
uninhabitable. Man could survive on Mars only by living inside glassite
domes and wearing space suits when he went outside of them. Except by
day in the warmer seasons it was too cold for him. The air was too thin
for him to breathe and long exposure to sunlight--less filtered of rays
harmful to him than on Earth because of the lesser atmosphere--could
kill him. The plants were chemically alien to him and he could not eat
them; he had to bring all his food from Earth or grow it in hydroponic
tanks.

       *       *       *       *       *

For fifty years he had tried to colonize Mars and all his efforts had
failed. Besides this dome which had been built for us there was only one
other outpost, another glassite dome much smaller and less than a mile
away.

It had looked as though mankind could never spread to the other planets
of the solar system besides Earth for of all of them Mars was the least
inhospitable; if he couldn't live here there was no use even trying to
colonize the others.

And then, in 2034, thirty years ago, a brilliant biochemist named
Waymoth had discovered daptine. A miracle drug that worked not on the
animal or person to whom it was given, but on the progeny he conceived
during a limited period of time after inoculation.

It gave his progeny almost limitless adaptability to changing
conditions, provided the changes were made gradually.

Dr. Waymoth had inoculated and then mated a pair of guinea pigs; they
had borne a litter of five and by placing each member of the litter
under different and gradually changing conditions, he had obtained
amazing results. When they attained maturity one of those guinea pigs
was living comfortably at a temperature of forty below zero Fahrenheit,
another was quite happy at a hundred and fifty above. A third was
thriving on a diet that would have been deadly poison for an ordinary
animal and a fourth was contented under a constant X-ray bombardment
that would have killed one of its parents within minutes.

Subsequent experiments with many litters showed that animals who had
been adapted to similar conditions bred true and their progeny was
conditioned from birth to live under those conditions.

"Ten years later, ten years ago," the Head Teacher told us, "you
children were born. Born of parents carefully selected from those who
volunteered for the experiment. And from birth you have been brought up
under carefully controlled and gradually changing conditions.

"From the time you were born the air you have breathed has been very
gradually thinned and its oxygen content reduced. Your lungs have
compensated by becoming much greater in capacity, which is why your
chests are so much larger than those of your teachers and attendants;
when you are fully mature and are breathing air like that of Mars, the
difference will be even greater.

"Your bodies are growing fur to enable you to stand the increasing cold.
You are comfortable now under conditions which would kill ordinary
people quickly. Since you were four years old your nurses and teachers
have had to wear special protection to survive conditions that seem
normal to you.

"In another ten years, at maturity, you will be completely acclimated to
Mars. Its air will be your air; its food plants your food. Its extremes
of temperature will be easy for you to endure and its median
temperatures pleasant to you. Already, because of the five years we
spent in space under gradually decreased gravitational pull, the gravity
of Mars seems normal to you.

"It will be your planet, to live on and to populate. You are the
children of Earth but you are the first Martians."

Of course we had known a lot of those things already.

       *       *       *       *       *

The last year was the best. By then the air inside the dome--except for
the pressurized parts where our teachers and attendants live--was almost
like that outside, and we were allowed out for increasingly long
periods. It is good to be in the open.

The last few months they relaxed segregation of the sexes so we could
begin choosing mates, although they told us there is to be no marriage
until after the final day, after our full clearance. Choosing was not
difficult in my case. I had made my choice long since and I'd felt sure
that she felt the same way; I was right.

Tomorrow is the day of our freedom. Tomorrow we will be Martians, _the_
Martians. Tomorrow we shall take over the planet.

Some among us are impatient, have been impatient for weeks now, but
wiser counsel prevailed and we are waiting. We have waited twenty years
and we can wait until the final day.

And tomorrow is the final day.

Tomorrow, at a signal, we will kill the teachers and the other Earthmen
among us before we go forth. They do not suspect, so it will be easy.

We have dissimulated for years now, and they do not know how we hate
them. They do not know how disgusting and hideous we find them, with
their ugly misshapen bodies, so narrow-shouldered and tiny-chested,
their weak sibilant voices that need amplification to carry in our
Martian air, and above all their white pasty hairless skins.

We shall kill them and then we shall go and smash the other dome so all
the Earthmen there will die too.

If more Earthmen ever come to punish us, we can live and hide in the
hills where they'll never find us. And if they try to build more domes
here we'll smash them. We want no more to do with Earth.

This is our planet and we want no aliens. Keep off!




Transcriber's Note:

    This etext was produced from _Amazing Stories_ March 1954. Extensive
    research did not uncover any evidence that the U.S. copyright on
    this publication was renewed. Minor spelling and typographical
    errors have been corrected without note.