Answer:
Prehistoric
Explanation:
The Prehistoric Period—or when there was human life before records documented human activity—roughly dates from 2.5 million years ago to 1,200 B.C. It is generally categorized in three archaeological periods: the Stone Age, Bronze Age and Iron Age.
Human evolution known to be a process in which species adapt to certain
conditions of life, and in the battle of life and death, they are forced
to become stronger in order to survive in this world. Diseases have
always been present during the evolution, acting themselves as a natural
selectors - the weaker organisms get sick and die. Not just humans, but
all species have to establish a great protecting mechanism in order to
survive. That is how our bodies are built, to be able to withstand and
survive in the conditions we live in, and that is why our immune system
has to be taken care of.
