In time, those RNA chains would double up on themselves into DNA, and RNA would resort to merely being a tool for translating and transcribing DNA for replication. With DNA as its blueprint, single-celled life experienced explosive growth everywhere along Earth's oceans where conditions were suitable. One particular organism, the first cyanobacteria, through natural selection, developed the ability to convert water and carbon dioxide into sugars by using the sun's energy in a process called photosynthesis. The byproduct of photosynthesis was oxygen, and these cyanobacteria flooded the atmosphere with large quantities of it, fundamentally shaping life systems to this day.
Over time, these different organisms would continue to evolve in new and specialized ways to fill niches within the environment. Again, natural selection pushed organisms towards specific specializations to display certain attributes and characteristics, not because of any intentional effort, but instead mutations that drove those elements of species were advantageous. Single-celled life had organisms that would evolve to multicellular ones. Plants and animals would produce a multitude of diverse species, each falling under different categories with capabilities suited to their environments, but ultimately many more died as they were unable to survive and replicate themselves under such dangerous conditions. Bacteria, plants, fish, reptiles, amphibians, mammals, birds, and many more would come and go, being put to this test. Many would fail in changing environments while others would migrate to new environments, and future generations would undergo new conditions in which they would be tested. Alas, we are jumping quickly through the tree of life, a visual display of Earth's life descending from today through the first microbes, but we need to get to the discussion of something most pertinent.
Towards the end of the dinosaurs, mammals were small, weak prey to them. With their demise, thanks to the severe change in the environment, instigated by a meteorite impact on the Yucatan, they were no longer able to survive effectively. They were big, and subsequently required a lot of energy to keep their bodies functioning. There was a massive dying-off of plant life from the impact since that caused large quantities of Earth to disperse throughout the atmosphere blocking necessary light for photosynthesis. Without large amounts of plant life, the big herbivores died. Without the big herbivores, the big carnivores died. For the time, therefore, being large was disadvantageous, and the small had their moment. This is where early primates would eventually come in, because chaos breeds opportunity.
As Professor Solomon states,
“Extinctions are an import part of evolution because, as the saying goes ‘nature abhors a vacuum.’ Extinction creates opportunity for other species to evolve to fill niches in an ecosystem.”
Primates are big-brained, social animals adept at tool manipulation due to their development of opposable thumbs. One such subspecies of primate was humanity and all our associated brethren. We are of the genus homo, descended from Australopithecus approximately two million years ago. Homo habilis, the first humans, originated on the African continent, and eventually evolved into homo sapiens, which is all modern humans, and spread throughout the world. They interbred with other subspecies within the homo genus, such as Neanderthals and Denisovans. Those subspecies may be gone, but their genetic code resides in the genomes of human races that originated in Europe and Asia, respectively. Regardless, homo sapiens almost didn't make it themselves, and our ancestors' fitness was put to the test.
"The populations of many large mammals shrank some 70,000 years ago. The eruption of the Toba volcano on the Indonesian island of Sumatra sent enough ash into the atmosphere that it likely disrupted the Earth's climate for several years. Humans were among the many casualties, and we nearly became extinct. Comparison of modern human genomes shows that all humans living today appear to descend from a population bottleneck of only 10,000 individuals that lived about 70,000 years ago. So humans just barely avoided the sort of extinction vortex that wiped out a lot of other large animals, including all the other humans. We became the lone survivors, the only descendants from a widespread and diverse group, unlike anything that previously existed on Earth. Our closest relatives have all become extinct."
The resulting 70,000 years of human migration throughout the world was able to create only minor genetic divergence throughout our species. The many varied biomes throughout the world allowed for this divergence. Humans underwent many relatively small microevolutions as they adapted to their environments. Changes in skin color, the distribution of body hair, facial features, and some other attributes didn’t do much to diverge genomes of the many groups. When compared to chimpanzees, we appear to lack significant genetic diversity as a result of that bottleneck. Those primary ethnic differentiators, such as facial features and skin color, are therefore somewhat superficial; genetically speaking.
For example, gene SLC24A5 plays a significant part in whether you have an increase or decrease in your melanin index. While other genes can impact various melanin attributes, this one gene establishes the primary difference in the dark skin of Sub-Saharan Africans and the light skin of Europeans. You get this change by simply converting guanine to cytosine in that SLC24A5 gene. To put it into perspective, say you were to write the letters of the genome in its entirety, you would have a stack of double-sided paper, size 12, Times New Roman font, approximately 60m (200ft) tall. Around 600,000 pieces of paper with 2,622 words on each side and all you do is change a letter on one of those pages within the stack from a "G” to a “C” or vice-versa.
The reason for the mutation of the SLC24A5 gene, or the reason for why it was able to propagate in Northern European regions, is that it provided a distinct advantage in that environment over darker skin. The human body uses sunlight to break down folic acid within the skin in order to produce Vitamin D. Vitamin D, which plays an important role in cell division among other things, is the only vitamin developed naturally by the body, and sun exposure is the primary method for getting it. Sunlight is important for human health, but too much ultraviolet light from the sun can also damage the DNA within your skin cells increasing the risk of cancer.
Humans developing in low sunlight areas would therefore benefit from a lower melanin index so that they could produce more Vitamin D. Humans developing in high sunlight areas would benefit from keeping dark skin since they already produce the necessary amount of Vitamin D while reducing risk of damage to skin cells. That isn’t to say that either can’t survive without that advantage, but they may not thrive when in competition with those that do. Additionally, human intelligence has help compensate for these disadvantages with the employment of clothing and sunscreen to block ultraviolet rays when the skin would receive too much sun, as well as Vitamin D supplements when receiving too little.
In another example of genetic mutation resulting in increased survival, we have the case of a change that isn’t necessarily good, but instead a lesser of two evils. In parts of Sub-Saharan Africa where malaria was prevalent, some humans developed a mutation to a gene that altered the shape of red blood cells. Within the 11th Chromosome of the human genome there is a gene called HHB, or beta globin, which deals with the construct of the protein within red blood cells. The gene itself is 438 nucleotide pairs long within the strand, and by changing a single nucleotide within it from an adenine to thymine, it alters the traditionally donut shape of the red blood cell to that of a sickle.
This sickle cell is more resistant to being infected by malaria since its tight shape prevents the parasite from developing effectively within it. The downside is that with two sickle cell alleles from both parents, the resultant condition called “Sickle Cell Disease” will cause an excess in these sickle shaped cells having difficulting flowing through the bloodstream which can lead to significant pain, damaged tissue, and death. Regardless, in a malaria-rich environment the sickle cell mutation increases survivability to a greater extent than it kills, meaning more people are able to live long enough to then pass on that trait when they have offspring.
Regardless of how we interpret modern human genetics one things is clear based on the story of our genomes. The truth is that humans, irrespective of where we look, lack significant genetic diversity. The biggest differences that we physically see: skin color, bone structure, hair thickness, eye shape, etc. can be summed up in the difference of a handful of nucleotide changes in various genes here or there. We are basically all the same, more so than other primates. Of the difference that societies of humans have about each other, they have less to do about what we are, and all to do about how we perceive it.
That perception is key to every endeavor a human being conducts; either as an individual or as a group. A human genomic links originating in Africa, Europe, Asia, or the Americas are all inherently linked further back to that group hailing from Africa. All homo sapiens descend from homo erectus at the very least, and some genomes of a few relatives still exist in humanity’s disparate ethnic groups. This means that how they perceive the world around them, and their place in it is based almost solely on external influencers.
Perception is an important topic to cover as everything we do in life is based upon how we perceive the results of our actions. In the subsequent section, we will discuss how the human brain functions, how it impacts our perception of our world, and how that shapes societal constructs and norms. It is these that shape human perception which in turn we act upon. We differentiate between threats and opportunities based on how we perceive them, and this leads to established principles and tenets for the conduct of conflict and partnership, war and business, but fundamentally they are the same thing. That fundamental thing is that all human endeavors seek to influence other humans, and their environment, for their benefit. Creating advantage so that they may thrive. But before we begin that discussion, we can discuss the implication that evolution has had on the development of these principles and tenets of warfare and business.