Why Do Humans Have So Few Genes?

I don’t quite know how to categorize the following post, because while it is fundamentally more physical anthropology, the whole issue that is being addressed is cultural. See, geneticists have been shifting the number of human genes for some time now. A good estimate is that humans have a little under or around 30,000 genes. You maybe confused, thinking, “Hey the human genome has been sequenced! Why are we working with estimates?” Well the human genome has been sequenced but there are gaps. Lots of them. There were two ways the human genome was sequenced, and the way that prevailed was the quick and dirty way.

Aside from having a hastily assembled genome, we really don’t know what a gene is. That definition shifts far more often than the number of genes in a particular genome. Once upon a time, a gene was a unit of heredity. It still is, but that definition is too vague. A gene is now any sequence of DNA that is transcribed. It doesn’t have to be a transcribed then translated into a protein, because there are a lot of products from a sequence of DNA that functions just dandy as RNA.

So now that we have an understanding of what a gene can be, it gets more complicated because genes are modified a lot in non-bacterial organism (i.e. us!). After being transcribed, an RNA molecule can be spliced or edited. Sections can be cut out here or there or even there or here. This process is called alternative splicing. So from one gene, many different products can be made depending on how it is edited or used. That begs one to ask then, is it not the number of genes that an organism has but the number of ways it can be alternatively spliced?

You’d think that’s what people would be asking, especially if they are scientists, but apparently a lot of people have their panties in a wad about the small number of genes we have. At least that’s what the science writers are touting out there. They keep rekindling the flame that we have almost as many genes as nematode, you know those tiny microscopic worms! That bugs a lot of people. Especially those that think humans are the greatest things to ever roam the Earth. People want to think they have the most; the most intelligence, the most prowess, the most genes. And the disappointment that has come with the fact that we don’t have that many genes, plays out as an ego deflation, which is exactly where the cultural aspect comes into play.

While humans are extraordinary in our own respects, we are predisposed to think of ourselves as the end all be all of evolution. Often we ponder how will we evolve, as if it is an answer even worth solving. This is a problem. And I think anthropology should step up to the plate and address it. We are ultimately in the business of explaining what it means to be human — so why do we think we have to have the most?

It seems like biochemist Dr. Larry Moran, who writes in his blog Sandwalk, also sees this problem but in a much different light. He nails one of Science‘s top questions, “Why Do Humans Have So Few Genes?” as a matter of ignorance on behalf of science writers — and I’m relieved that he has at least addressed it. I’m relieved that there is some sanity out there amongst the scientific community. Here’s exactly how Dr. Moran has phrased is argument,

“[This is] a very “wrong” question that reflects an ignorance of the scientific literature and a profound misunderstanding of evolution, developmental biology, and gene expression. Humans have exactly the number of genes that we expect. They don’t need to have many more genes than fruit flies or worms because a small number of unique genes are all that’s required to make significant differences in development. They don’t need to have special complexity mechanisms to “explain” anything because there’s nothing that needs explaining. Human genes are fundamentally the same as those in Drosophila melanogaster (fruit fly), Caenorhabditis elegans (nematode worm), and Arabidopsis thaliana (a small flowering plant).

This “top 25 question” illustrates exactly the problem that I alluded to earlier. You don’t recognize the important questions in science by polling science writers and editors. The “right” questions are the ones being asked on the frontiers by the creative experts who are thinking outside the box. This is an “inside the box” question and very few of those ever turn out to be important.”

Dr. Moran, you are right. This is a non-sensible question to even bug ourselves with and I agree that science writers shouldn’t always be asking the important questions. However, I see the blame ultimately come down to our modern day cultures. We have disengaged ourselves so much from the rest of the living world that we can’t fathom to think there are living things with bigger genomes than our own. Our science writers are merely appeasing to the ignorance of the general public. This is what the masses want answered. The unanswerable tripe. I consider it a sad revelation, more of an ego deflation that this is what we preoccupy our collective minds with than the number of our genes.

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