Man, it seems, did not want to be healthy.
He ate of the Tree of Knowledge.
Once he did so, the only choice was to start on the way of artificial cure and correction.
One is reminded of the fact that Eskimos never knew what an ordinary cold was.
Once they were infected by civilized man, they had no resistance to it and they died by the hundreds.
What happened to man because of the Tree of Knowledge is not very different.
He caught a cold.
And indeed, what occurred was no closer to the depths of evil than a sniffling nose.
It was only afterwards that man invented the subtleties and forces of corruption.
But at the time it was enough for his vulnerable, innocent existence.
His soul did not have any resistance against the sickness of evil.
–Rabbi Adin Steinsaltz
From In the Beginning, “The Two Ways of Tikun,” p. 104, by Rabbi Adin Steinsaltz