In the fifth decade of the nineteenth century, Charles Darwin signed on as naturalist aboard the HSM Beagle. The ship and Darwin would travel the globe and Darwin painstakingly recorded and classified the many species he observed in different ports of call. At one small group of islands called the Galapagos, Darwin noted that species on one island exhibited differences from the presumably same species on other islands. How could this be he wondered.
As a naturalist, Darwin kept incredibly detailed and thorough notes and upon return to England he began a review of his observational data. It became obvious to Darwin, that species sporting different attributes in the Galapagos were, in fact, variations sharing a common ancestral heritage, and that somehow there was a process at work causing inhabitants of unique islands to change their characteristics to suit the microenvironment they found themselves in.
Darwin formed a hypothesis he called the theory of variation and natural selection, elaborating on it in his book Origin of Species with his characteristic attention to detail. Darwin stumbled upon the scientific fact we today refer to as biological evolution, but he didn’t have a clue to what caused it or how the variation he reasoned motivated it was manifest. He, Darwin, had run into the tip of the proverbial iceberg of heredity and genetics, but it would take another hundred and fifty years before scientists would discover the greater body of intrinsic evidence to substantiate and prove that Darwin’s theory was factually accurate.
The discovery of nucleic acids and biological macromolecules in the 1950’s, set the stage for a virtual explosion of human knowledge with respect to the chemistry taking place in eukaryote cells; leading to the mapping of the entire human genome consisting of about 3 billion nucleotides. Humans, being the most complex creatures to have evolved on planet Earth by virtue of our anatomical brain and the cognitive state it facilitates, tend to look for complexity in our understandings of natural phenomena. As Albert Einstein noted, nature is simple and it is we humans who devise complicated notions to explain it.
With respect to life and the genetic variation and evolution it evinces from, mankind has long sought complicated explanations necessitating some divine intervention of intelligent design ordaining and orchestrating the multiplicity and proliferation of chemical reactions which are life. In fact, we have found that life is much less complicated than anyone had before envisioned. At its rudimentary level life is just a mistake, a proliferation of genetic polymorphisms precipitating genetic variation and driving evolution.
It all comes down to a natural bio-chemical process called mitosis involving a number of enzymes that cause double stranded DNA molecules to bifurcate into two separate strands, each then being rebuilt into an identical copy of the original. But far more often than not, the resulting new DNA molecules are not exactly identical. In fact, it is far more likely that each time a DNA molecule is replicated a number of single or multiple nucleotide polymorphisms will occur. In some cases, nucleotides are replaced with completely different ones and in others one or more nucleotides may be deleted entirely or new ones inserted where they did not exist before, causing what are referred to as frame shift errors.
Fortunately, less than one percent of human DNA accounts for active genes, those that code for proteins. The rest of it is telomeres, remnants of extinct damaged genes, and genetic switches usually positioned close to a gene and which when chemically switched on by a specific enzyme, cause the gene to be expressed. If an error does occur within an active gene it will effect the host cells function usually causing the death of the cell or some more grotesque manifestation of disease like cancer. If the cell continues on it will make more an more copies of itself, propagating the genetic variant to future descendant generations of the cell.
The earlier in its development a genetic mutation occurs in an organism, the more likely that mutation will contribute to variation in the species. It’s simply a matter of math. A genetic mutation happening early in the embryonic state, when the being consists of just a few cells, will be pronounced in more of the organisms cells as these early cells divide. Such variation is also far more likely to be propagated beyond the individual organisms to future generations. If it is a mutation providing some advantage to an organism with respect to its environment, the species will proliferate. If it results in a disadvantage the species will become extinct. That is the process of variation and natural selection reduced to its simplest form.
Some time during the last ice age, a genetic mutation occurred during the embryonic development of one human individual causing that individuals eyes to be colored blue. All people alive today who have blue eyes can trace their heritage back to that specific genetic variant in that specific individual. When there is a population explosion among a given species the potential for variation in that species increases and evolution of the species is accelerated.
When humans first began to domesticate dogs there weren’t as many different breeds or subspecies as exist today, but humans accelerated diversity by crossbreeding and introducing an element of selective variation in this animal species. In addition, humans have provided an artificial environment for dogs while breeding out some of the characteristics which once aided dogs in their survival. If for any reason humans were no longer around to care for domesticated dogs, many of their subspecies, subject to an environment they couldn’t cope with, would become almost immediately extinct.
In nature this occurs too, when a given species becomes so evolved in to a specific environmental niche, that if anything happens to change that environment they are unable to cope or adapt. But it only takes one mating pair of a species to survive by virtue of some quirk of fate or by having some genetic variation giving them an advantage, and new forms of the species will evolve to continue its linage.
In 2005, a chimpanzee’s genome was fully sequenced for the first time revealing its genetic blueprint. Gene for gene, the differences between humans and our ape cousins now appear far more subtle than ever before suspected and the notion that we share a common ancestor 5-7 million years ago, just as people with blue eyes and other variants do in our own species today, is now an obvious certainty. But evolution of a larger brain in humans has given us an advantage and our species has proliferated to every corner of the planet while chimps remain relegated to the small environmental niche that sustains their species.
Contemporary humans, by simple fact of possible permutations of 12 billion sets of 23,000 specific genes, are more susceptible to variation than ever before. Some where out there in the world are individuals who will develop genetic variations that will become dominant in future generations. We have already seen this happening with respect to genetically inherited diseases like sickle-cell in Africans or hemophilia in Europeans, both of which are variants that effect blood cells. Within as few as a hundred generations, altogether new subspecies of humans could evolve, and once again their could be multiple versions of cognitively endowed species walking side by side on the planet, as was the case 30,000 years ago when Neanderthals were the dominant hominid species and anatomically modern humans a new arrival. This then, is the process of genetic variation and the evolution of species.
