not so sure it's foolishness," Tiger Martin said slowly. "Jack,
maybe he's got something. A couple of things would fit that don't make
sense at all."

"All sorts of things would fit," Dal said. "The viruses we know have to
have a host--some other life-form to live in. Usually they are
parasites, damaging or destroying their hosts and giving nothing in
return, but some set up real partnership housekeeping with their hosts
so that both are better off."

"You mean a symbiotic relationship," Jack said.

"Of course," Dal said. "Now suppose these virus-creatures were
intelligent, and came from some other place looking for a new host they
could live with. They wouldn't look for an intelligent creature, they
would look for some _unintelligent_ creature with a good strong body
that would be capable of doing all sorts of things if it only had an
intelligence to guide it. Suppose these virus-creatures found a
simple-minded, unintelligent race on this planet and tried to set up a
symbiotic relationship with it. The virus-creatures would need a host to
provide a home and a food supply. Maybe they in turn could supply the
intelligence to raise the host to a civilized level of life and
performance. Wouldn't that be a fair basis for a sound partnership?"

Jack scratched his head doubtfully. "And you're saying that these
virus-creatures came here after the exploratory ship had come and gone?"

"They must have! Maybe they only came a few years ago, maybe only months
ago. But when they tried to invade the unintelligent creatures the
exploratory ship found here, they discovered that the new host's body
couldn't tolerate them. His body reacted as if they were parasitic
invaders, and built up antibodies against them. And those body defenses
were more than the virus could cope with."

Dal pointed to the piles of notes on the desk. "Don't you see how it
adds up? Right from the beginning we've been assuming that these
monkey-like creatures here on this planet were the dominant, intelligent
life-forms. Anatomically they were ordinary cellular creatures like you
and me, and when we examined them we expected to find the same sort of
biochemical reactions we'd find with any such creatures. And all our
results came out wrong, because we were dealing with a combination of
two creatures--the host and a virus. Maybe the creatures on 31 Brucker
VII were naturally blank-faced idiots before the virus came, or maybe
the virus was forced to damage som