That's a good question. I can imagine that there was a time before there was life on Earth, and then clearly there was a time X-hundred thousand years or a million years later when there were things that we would all recognize as biological.
A high count indicates the presence of inflammation in the body. Because white blood cells are calculated by the number of cells per volume of blood, test results can vary between labs. Different labs use different degrees of measurements for the white blood cell count.
Some causes are bacterial, viral, fungal or parasitic infections, cancer, hemorrhage or exposure to chemicals or medications. A differential white count gives more specific, targeted information as to which leukocytes levels are elevated. Leukopenia is a lower than normal white blood cell count. Common causes are leukemia, chemotherapy, radiation therapy and aplastic anemia. White Blood Cell Differential The white blood cell differential looks at the number of each type of white blood cell for a given blood volume.