The changing of a habitat for a given species, whether voluntarily or involuntarily.
Much of the way we are shaped by evolution is indicative of the kind of environment we had to survive in. Early records show that we, as humans, had to survive at one point in trees as we often see modern primates do. Many primates today are confined to forests, whereby they have developed mechanisms physiologically to be able to climb high distances, especially given the usage of their opposable thumbs. In addition, the diet that keeps them nourished is very indicative of living in trees, such as having to seek out fruits like bananas that may grow at a higher altitude. Therefore, a major question for someone who does not understand the concept of evolution is how we are living as Homo sapiens today despite there still being monkeys in the wild. Many people choose to understand evolution as a “progression toward perfection.” This is a common misconception – evolution is not a progression toward perfection. In fact, the idea of “perfection” is highly debatable – what exactly constitutes a “perfect” organism? Evolution is simply biological and psychological changes in an organism that are best suited and adapted for survival in their respective environment. A classic example is Darwin’s discovery of finches on the Galapagos islands. Their beaks are by no means perfect, but their beaks were also well-suited to be able to eat the kinds of foods that were best suited for that respective bird’s diet. A similar concept is true between chimps and humans – the reason chimps continue to look the way they do is due to the environment that they are in. They are in an environment whereby getting to high elevations is essential to not only find food sources but to also have a better visual scope of the environment around them and avoid predators. Humans, on the other hand, do not have the mobility and grip strength that is evident in primates, as we have a much harder time climbing than do many modern monkeys. We also stand in an upright posture with our spines straight, and walk with what is called bipedal locomotion, or the ability to walk on two legs. Monkeys often depend on their arms as a means of locomotion, as is evident in the way many primates walk, such as gorillas. This difference, however, is by no means a coincidence, nor did we evolve such a difference because of “perfection.” The difference lies within specifically habitat change. Given that we have so much in common genetically with modern primates, there had to have been some kind of change or a point at which a divide was necessary and occurred to have so much genetic similarity but such a monstrous difference in behavior and physicality. The bigger question that evolutionary scientists are still trying to figure out to this day is precisely, “Why and how did this change occur?”
Our Original Habitat
Oddly enough, one of the key components that demonstrates how our early ancestors may have lived in trees is exhibited by our shoulder development. Genetically, we are most similar to chimpanzees and also share their shoulder structure most similarly. Despite us sharing most of our genetic similarity with apes, it seems as though our shoulder development is actually more similar to orangutans than other apes, suggesting that at some point we had a mechanism by which we had to swing between trees in the way orangutans do. Through studying evolution, we must operate under the assumption that no physiological change is the result of a mere coincidence, rather, there must be some adaptive purpose to have developed the kind of structure the organism did. In this case, there must be some reason why we share so much genetic similarity with other apes, but our shoulders specifically seem to model orangutans that swing between trees as compared to heavier apes (Young et al. 2015).
If we did indeed live among the trees, then an obvious question of course would be why we ever had a reason to move out if our bodies were already accommodated to living in those conditions for survival. The answer is not fully understood, although there are an abundance of theories that attempt to explain why through various means of measurement. As will be discussed in later chapters, there are numerous popular theories such as climate change or simply being pushed out by other animals that could explain why we eventually moved out of the trees after successfully living in them for such a long period of time. (Potts 1998)
The climate theory, in short, essentially states that there are constant fluctuations in our climate that can have profound effects on our environment. The theory also states that the fluctuations in climate are more dramatic than ever, especially with the advancement of the industrial revolution and the ever-increasing population, having a more profound effect on the environment than ever. However, we also see climate change far before human civilization, whether due to catastrophes such as volcanic eruptions, the supposed meteor that wiped out the dinosaurs, or even the last ice age that wiped out vegetation and livestock across many continents. Therefore, it is suggested that perhaps some kind of major catastrophe happened at the time that would result in a change in the local environment. Thus, a lack of vegetation or even deforestation resulting in a lack of trees would have made survival infinitely harder for primates and early hominids, and thus they likely decided to migrate further down to look for resources that would be scarce at higher elevations (Demenocal 2004). This also likely resulted in a population bottleneck or an event that significantly decreases the population of a given organism. These changes likely resulted in the vast majority of our species dying from either being unable to survive in the trees due to lack of resources or moving onto the forest floor and being unable to survive due to new predators and an unfamiliar environment (Potts 1996). Those that did survive, however, likely were eventually able to migrate out onto the African grasslands, where they then started experiencing evolutionary change over the course of millions of years to adapt to their new environment.
Another such theory is that we simply got “bullied out” by our ancestors which would eventually become modern day primates. It is possible that they gained some kind of evolutionary advantage that allowed them to get resources faster than early hominids could, giving them no choice but to move to another location to ensure survival. Again, those that could survive did, but it likely resulted in a massive decrease of the population whereby migrating to a new environment and reproducing with viable mates was the only way that the species could survive. As a result, the species slowly but surely had to make adjustments neurologically and physiologically to accommodate for an environment that they were not evolutionarily suited for, similar to the evolutionary mismatch effect. (Foley 1994)
Given that grasslands were often much higher in visibility due to the lack of obstruction from trees and a wider horizon, it became pivotal that our vision and hunting skills change. Hence, we developed bipedal locomotion as a more efficient means of traversing the grasslands and being able to hunt our prey. We adapted from having short bursts of speed and having the strength to be able to climb trees and instead endure long distance running to tire out our prey, as well as our shoulders changing to be able to accommodate for weapon making and throwing. It was precisely this change that paved the way for eventual Homo sapiens, given that with the ability to make weapons, we evolved from a creature that was confined to trees and using our body as our means of hunting prey and instead creating objects that we can attack prey with from a distance – maximizing resources and food and minimizing risk. With this cycle came a population resurgence and therefore eventually the entire hominid species moving out into the African savannah.
The African Savannah
The savannah represented a radical departure from the forest that we had previously lived in, and therefore the reason we see ourselves as so different from chimps is because of that divide that occurred to keep them in trees and us on the grasslands. The chimps had no reason to have to change given that whatever the reason may be (climate change, being pushed out by predators or our ancestors, or another reason we have not been able to deduce), they were able to survive in the trees whereas early hominids could not. While the hominids’ new environment requires new means of adaptation to be able to hunt different kind of prey on a different terrain, the primates kept doing what they had been doing all along. This, in essence, is the answer to why we have evolved into Homo sapiens, but monkeys still exist – they simply had no reason to change given that they continued to live in the environment that their bodies were always suited to, as they continue to do today. Hominids were forced out, and therefore the evolutionary changes we see in ourselves today that differentiate us from primates are remnants of how we would survive on the savannah (Reed 1997).
Savannahs typically have a wider horizon, and therefore our vision became essential to not only avoid being killed by predators but to more easily seek out prey that represented food and a means to survive as a group. As such, our spines began to straighten out rather than have curvature and we developed bipedal locomotion. Not only did this allow us to traverse long distances, but it made a huge difference in terms of our vision and even our communication. Instead of lifting our heads to look at what was in front of us, we now could look at our surroundings with ease and could turn our heads horizontally in a manner that was not possible before. This was no coincidence, of course, as the savannah is often called “flatlands” for their constant altitude and lack of elevation – generally, it was important to be able to have a wide scope of view of the entire landscape and to see as far as the horizon to be able to hunt for prey. Not only did this structural change help our vision, but it also helped us communicate with other hominids. By being able to look directly at their face, face-to-face communication became much easier, by being able to read emotions and eventually develop language and dialects that allowed for more coordinated execution of group activities. As a result, enhanced communication came which would eventually lead the way to more advanced concepts such as music, stories, and much of the art world we see today in the form of human creativity.
Our habitat change was essential to the way that we have developed physiologically as Homo sapiens. We now stand in an upright position because of bipedal locomotion, which gave us an enhanced and extended scope of vision, as well as enhanced communication which led to the development of speech and language. Getting out of the trees also allowed for free use of our upper body that was previously essential to be able to walk as well as swing from tree to tree. Our shoulder muscles then evolved to be able to do things such as create weapons and more importantly throw them, maximizing our potential as predators in the environment to hunt prey. The ability to throw objects was essential to survival especially on the African savannah, not only given the newfound predators and the lack of obstruction from trees, but also simply to maximize reward by attacking animals from a distance, but also minimize risk by avoiding getting close to potentially dangerous animals. In short, many people fail to understand the concept of evolution by not comprehending why chimps are still in the wild today, but humans exist alongside them. This difference is explainable by our division from chimps for a number of possible reasons, such as climate change or being pushed out by other predators or ancestors. Ultimately, habitat change was paved the way for us to evolve into the Homo sapiens we see ourselves as today, physiologically and with our remarkable ability at communication and cooperation.