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.
A low white blood cell count can be caused by a range of different conditions, from diseases to bone marrow failure, according to the National Institutes of Health. It can also be caused by a vitamin deficiency, though not generally as a result of a B-12 deficiency.