How many cells are in your body?
Each cell has a life span of from a few days to a lifetime. While red blood cells live for about four months, white blood cells live on average more than a year. Skin cells live about two to three weeks, while colon cells die off after about four days. Sperm cells have a life span of only about three days, while brain cells typically last an entire lifetime.
As each cell dies, they are being replaced by a new cell fully-loaded with its own set of specific DNA instructions for that functioning of that cell, as well as the entire genome of the body.
Most human cells carry 2 copies of the genome and are known as diploid cells. One copy comes from each of your parents, so they aren’t identical, but similar. However, sperm and egg cells only carry one copy of the genome and are known as haploid cells. During fertilization, the 2 cells merge their copies and make a diploid zygote. At the chromosomal level, humans have 23 chromosomes, so a diploid cell has 2 copies of each so a total of 46 chromosomes.
As the body matures, cells are dying off and being replaced all the time, so it’s not clear where the popular myth began that cells are renewed every seven years. I remember hearing this when I was a monk as many of my teachers would claim as such to prove how the body is changing while the soul remains constant. I just accepted this as a fact but it turns out the cell lifecycle is much more variegated.
Naturally, cells cannot communicate with us to help us unravel this mystery. Certainly, we can look through a microscope and count off the number of cells in particular organs but this method is far from practical. While some types of cells are easy to spot, others weave themselves up into obscurity. Even if you could count ten cells each second, it would take you tens of thousands of years to finish counting the number of cells in one human body, what to speak of the challenge of chopping a body up into tiny patches for microscopic viewing.
The closest estimate for the total number of cells in a human body came from a study published in Annals of Human Biology, entitled rather appropriately, “An Estimation of the Number of Cells in the Human Body.”
The authors — a team of scientists from Italy, Greece, and Spain looked back over scientific journals and books from the past two centuries and found many estimates that presented a huge disparity, from 5 billion to 200 million trillion cells. What was more surprising was that none of these previous reports offered an explanation for how they came up with the estimate. It was all just conjecture and yet these were official scientific journals!
If it’s not feasibly possible to count all the cells in a human body, how can scientists estimate the total? One method proposed is to take the average weight of a cell, which is approximately 1 nanogram and multiply that by body weight. For the average adult man weighing 70 kilograms, a simple calculation would lead us to conclude that his body is made up of about 70 trillion cells.
It’s also possible to make an estimation based on the volume of cells. So if we take for example the average volume of a mammal cell, estimated at 4 billionths of a cubic centimeter, then we would conclude that this same 70kg male contains 15 trillion cells. Now that’s quite a disparity but what makes matters worse is that the cells that pack our bodies are not lined up in a uniform way. Cells come in different sizes and densities. If, for example, you used the density of red blood cells to estimate the total, your total number would be even higher — a staggering 724 trillion cells — because red blood cells are packed very tightly. Skin cells, on the other hand, are so spread out that they’d give you a measly total of just 35 billion cells.
So the authors of the above-mentioned paper set out to calculate the number of cells in the body by breaking it down by organs and cell types. They tallied the volume and density of cells in the intestines, gallbladders, liver, joints, and bone marrow, etc., and then came up with estimates for the total number of each kind of cell. For example, they estimated that we have just 2 billion heart muscle cells and 50 billion fat cells. By adding up all the numbers they arrived at 37.2 trillion cells.
Whether the actual number is 37.2 trillion or 200 trillion, both numbers are astronomical and should help us appreciate just how complex this human body is. If, as I mentioned earlier, it requires something like 100 pages of genetic code to instruct just one cell in our body to perform its particular function, then we’re talking about a genetic instruction manual for the entire human body of 37.2 trillion x 100 or 37,200,000,000,000,000 printed pages of text, or a book that would scale to 37.2 billion kilometers high! Another way to visualize this is that this distance would cover 3 visits to Pluto and back. And so the fact that Darwinian philosophers and scientists have the audacity to suggest that the human body evolved through random events is utterly absurd.
EXCERPT from The 7 Maxims for Soul Happiness by Paul Rodney Turner
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