Post Author: Bill Pratt
Ever since technology advanced to the point that scientists could map out entire genomes of various animals, we have been hearing how human beings are extremely similar to other mammals at the level of genes. These similarities always make news, but I have always found these similarities to be much ado about nothing.
After all, I can see with my very own eyes that humans and mice are massively different, so when biologists told me that mice and men were basically the same, I figured that their metric for comparison was being oversold.
In a NY Times article from 2002, Nicholas Wade wrote that “only about 300 genes — 1 percent of the 30,000 possessed by the mouse — have no obvious counterpart in the human genome.” So, we are told that humans and mice are 99% similar, based on their genes.
We have also been told that virtually all the information needed to construct a plant or animal is found in the genes which code for proteins, which would imply that the instructions for constructing a mouse are 99% similar to the instructions for constructing a human. This “fact” of biology never made sense to me, as I can see that mice and humans are constructed quite differently, far more than 1% differently, however we might want to count that 1%.
James Shapiro, in his book Evolution: A View from the 21st Century, explains that I wasn’t wrong after all. There is far more to the construction of an animal than the genes that code for proteins. Shapiro states,
The traditional view has been that related species differ in their repertoire of individual “genes.” But a more contemporary Evo-Devo perspective is that much of morphological change in evolution occurs by modification of expression through alteration of enhancers and other transcriptional regulatory signals, as well as distinct patterns of epigenetic formatting.
Translation: genes are not the only determinants of evolutionary body changes. There is a whole other world behind the genes that scientists have only recently been discovering. Shapiro continues:
Comparing mice and men, the “genes” stay largely the same, but their deployment differs. The bones, ligaments, muscles, skin, and other tissues are similar, but their morphogeneses and growth follow distinct patterns. In other words, humans and mice share most of their proteins, and the most obvious differences in morphology and metabolism can be attributed to distinct regulatory patterns in late embryonic and postnatal development.
The way I read this is that if we think of a human as a “house,” and a mouse as a different “house,” it is true that both houses are constructed with wood, cinder block, nails, glass, etc. That is what the genes give us, the raw materials of the house.
And that’s interesting, as far as it goes. But the actual construction of the house involves far more than raw materials. What is more important is the architecture, the drawings, that specify how the raw materials will be used to build the house. The mouse “house” is like a 100 square feet shanty, whereas the human “house” is like a 10,000 square feet exquisite mansion.
Sure, they are made out of similar materials, but to say that the shanty and mansion are 99% similar is grossly misleading, don’t you think?