This, of course, is only possible in Borges’ brilliant fantasy world. In real life, if you hold two books in your hand --for example, Cervantes’ Don Quijote de la Mancha and Menard’s Don Quijote de la Mancha--, and the books correspond word by word, or almost, you immediately smell a rat. The books must --to say the very least-- have a common ancestor. They can’t really be independent.
Odoriferous rodents of the same kind assail the discerning noses of biologists when they compare organisms from the present and from the past using the tools of old and new biological disciplines such as embryology, anatomy, genetics, and biochemistry. Charles Darwin’s original treatise was a steamroller of evidence for “descent with modification.” Today, evolutionists possess further detailed and consistent proof of the fact of biological evolution.
Consider the backbone in humans. Humans, as you probably know, walk upright most of the time. Our backbones are placed in the back (duh). But look at the famous roof at the Museo de Antropología, in Mexico City. Here it is:
A hypothetical Cosmic Engineer designing humans from scratch would have endowed us with sturdier “backbones” passing through the center of the torso, not along the back. As things are, we are well adapted to an upright posture, but not perfectly adapted, because we have only recently evolved from ancestors that went about on all fours. Imperfections such as are manifest in anatomical studies argue for evolution and against design.
Anatomy, physiology, embryology and other tools that were already available in Darwin’s time can probe only so deep into the similarities of organisms, and go only so far back in time. It is the more recently developed field of molecular biology that provides the most detailed and convincing evidence that we are all, from human to bacterium, ultimately related by descent from common ancestors.
The organic compounds known as aminoacids can be numbered in the hundreds, yet all bacteria, plants, animals and fungi synthesize all their proteins based on just 20 aminoacids, the same 20 for all living beings. Further, for all its staggering diversity, all life on Earth depends on the same few chemical pathways (fermentation, photosynthesis, respiration) to produce energy and build cell components. The molecular and chemical uniformity of life can only be accounted for by evolution.
Molecular biology is unique as a tool for comparative analysis of species in that it allows scientists to precisely quantify the degree of similarity of different organisms. The protein cytochrome c of humans is identical to that of chimpanzees. It differs by one aminoacid from that of rhesus monkeys, by 12 from that of horses, and by 21 aminoacids from that of tuna fish. Comparing the DNA of two species, molecular biologists can now even determine approximately how far back in time the species’ most recent common ancestor lived in the same way that linguists can tell how recently two languages diverged from a parent language by analyzing their similarities.
This is only a paltry sample of facts that can only be explained by evolution. Darwin himself provides many more in The Origin of Species. Today all scientists agree that, as Theodosius Dobzhansky, a leading evolutionist, once said: “Nothing in biology makes sense except in the light of evolution.”