Science Essay: The Human Evolution
Science and religion teach people two vastly different things when it comes to the evolution of man. In religion, particularly Christianity, believers are taught to believe that man came from the hand of God – that it is God who should be acknowledged for the creation of man as is known today. However, science shows – and provides evidence – that man was not created as is. That man came from now-extinct primates. This essay will discuss Charles Darwin’s theory of evolution.
What is human evolution according to Charles Darwin's theory?
The human revolution has long been the subject of debate between creationists and evolutionists. It is the process that led to the emergence of humans as known today. The naturalist British scientist Charles Darwin firmly believed that humans “descended from apes.” While scientists view this statement of his as something that can be dismissed – as humans and apes only share a common ancestor that lived about millions of years ago – creationists see this notion as an abomination.
Human evolution, according to Charles Darwin’s theory, occurred due to the process of natural selection. These two terms are often interchanged but it really means two different things. Evolution is focused on the change of a certain species – in this case, humans – goes through while natural selection refers to how organisms adapt to a change in their environment. It may be confusing, but an easy way to distinguish one from the other is remembering that the process of natural selection is the one that brought about evolution.
In his book The Origin of Species (1859), Darwin shared four points of natural selection that are vital to human evolution: variation in the population, which are the exhibited differences of individuals within a population in terms of appearance or behavior; inheritance of traits, how certain characteristics can be inherited from genetic parents and how some simply cannot be inherited and are just developed over time; capability of offspring, the number of offspring produced in each generation increases thus limiting the number of resources available thus dictating the mortality rate for that generation, and; survival of the fittest, which is where all three elements culminate.
Theories of Early Human Evolution
There are a number of theories that a non-scientific person has come up with regarding human evolution. One of the common misconceptions is that modern man directly descended from an ancient line of apes. Charles Darwin claims to never have made that statement and modern scientists just dismiss this. Another one is that there is a “missing link” of a certain now-extinct species between humans and apes that would solve the mystery of evolution once and for all. Aside from these, there are other theories that scientists recognize, like the savannah hypothesis, the aridity hypothesis, the turnover pulse hypothesis, and the Red Queen hypothesis.
The savannah hypothesis theorizes that hominins or apes originally lived in trees and walked using all four limbs. This was so until an event forced them to move out of the forest and onto a savannah where they began to evolve slowly and started to walk using only their two feet. The savannah hypothesis was further expanded into the aridity hypothesis which tells of how the earth began to lack a supply of water thus resulting in more savannah landscapes. Because of these certain conditions, the apes were forced to move out of their original habitat and adapt to a new way of life.
The turnover pulse hypothesis posits that changes in the environment is better taken by generalist species rather than specialist species. Changes in the environment sometimes result to extinction because of the inability to adapt. Generalist species have the ability to spread out or move locations when the environment changes but the specialist species would have no choice but to adapt and exhibit a greater rate of evolution.
The Red Queen hypothesis says that organisms need to evolve constantly in order to survive. Organisms encounter numerous changes in the environment they live during their lifespan and if they fail to adapt to certain changes, it would mean extinction for their entire species. For humans, improving cognitive abilities allows humans to gain influence over other humans and control resources.
The Stages of Human Evolution
Scientists found that it was about seven million years ago that humans started to evolve. However, the human tribe was found to have existed around 23 million years ago. From being closely related to primitive apes, living in caves, and having absolutely no knowledge of how to use tools to improve their way of life, humans have come a long way since then. The first modern humans, according to research, appeared recently about 200,000 years ago.
The “missing link” some people are referring to is not entirely wrong. Scientists just prefer that the term “missing link” not be used as the only thing they are yet to discover on the matter is the common ancestor the two species share. Between 23 million and five million years ago, the family Hominoidea split into two sub-families which were to become the lineage of apes and humans. This is where the supposed “missing link” comes in, as scientists have not yet zeroed in on the exact point where the two sub-families diverged.
The Dryopithecus is an extinct genus of ape species that lived 23 to three million years ago in Africa, China, India, and Europe. Although, they were found to have originated in Africa. They were believed to have been alive at a time when the Earth was densely populated with lush forests and tropical lowlands. They are believed to have been herbivores mostly due to their living conditions.
The second is the Ramapithecus. Its remains were first discovered in Punjab, then have also been discovered in Africa and Saudi Arabia. Like the Dryopithecus, they also lived in forests. They also resided in grasslands too. Their remains were found to have robust jaws, shorter canines, and relatively thicker teeth enamel. Like modern humans, they had an upright posture, walked on two feet, and used their hands to eat and defend themselves.
The next genus, Australopithecus, is the forerunner and is believed to be a close relative of the genus Homo. – if not its actual ancestors. The fossils of Austrolopithecus were also found in South Africa. An excellently preserved fossil found in Ethiopia was named Lucy. This genus also walked upright, had canine teeth smaller than apes’, canine teeth bigger than humans, and was believed to have known how to use stones as tools or weapons to gather their food.
The Homo species was first discovered in Java. It had a relatively larger cranial capacity than all the previous genus, stands upright on two feet, and has fully-developed opposable thumbs. Among this genus are the extinct species Homo erectus, Homo habilis, Homo heidelbergensis, Homo naledi, and the modern man, Homo sapiens. This genus is known to have largely used tools like stones and quartz in their everyday life, dwelled in caves, knows how to hunt, and learned how to use fire.
Homo sapiens neanderthalensis dwelled in Eurasia and some in Africa. Neanderthals were found to have mated with Homo sapiens and other species of archaic humans. Scientists are still figuring out how the event of mating with other human species started. The Homo sapiens neanderthalensis’ dwelling places were found to have been built out of limestone and they also knew how to work with fire and also knew how to best keep themselves warm. They were quite capable of hunting large animals.
Lastly, the ones known as modern humans are the species known as Homo sapiens. The first discovered remains of Homo sapiens was found in Europe. It was named Cro-Magnon and was found to have a reduction in the structure of the jaws and a rounded skull. Like the Homo sapiens neanderthalensis, their main source of food was done by hunting. It was during their era that the first traces of drawings on the cave wall were found and were mostly made up of animal figures.
Human Adaptations
The many eras have seen lots of changes in the human tribe. One of the main evolutionary human adaptations known is the fact that man has evolved from using all four limbs to walk to just using only two feet and reserving the two upper limbs to grab tools and such. Using two feet to transport oneself from one place to another enabled humans to reserve their hands for labor.
Furthermore, bipedalism gave humans the ability to endure long distances and duration spent on hunting and traveling. Being able to walk using two feet also reduced the burden of breathing as it is a significantly less taxing movement. Evolving to being an upright man also caused changes to the skeletal structure of man, especially in the lower regions of the body. It resulted in changes in the joints, toes, arms, spinal column, and pelvis.
Humans also developed a larger brain size as the Dryopithecus was known to have a brain as small as an ape’s. The encephalization – or evolutionary increase of the brain size - began in the genus of Homo. Specifically, in the species of Homo habilis. It was also observed that as a human grows older, the size of the brain also grows. This enabled humans to learn more and more skills that they can use to thrive in life.
Humans have also evolved to exhibit some physical differences between the two sexes. The bodies of male and female humans are very different from one another. This evolutionary characteristic is known as sexual dimorphism. The bodies of human males are slightly larger than females, they have more body hair, and less body fat while female humans exhibit a higher percentage of body fat, curved shape, and less body hair. Some of the differences between the two sexes may have been because of the fact that females are relied on to take care of their offspring.
Another notable evolution of humans is how humans now rely more on their sense of sight rather than their sense of smell. In the early days. Humans had to rely on their nose a lot because it is direly needed for hunting. Now, humans place importance on vision and no longer have a keen sense of smell. Modern humans find the sense of sight more important than other senses. Other human adaptations include reduced body hair, a much more pronounced chin, and a descended larynx.
Up to this day, humans are still evolving. The process of evolution is continuous. However, it is not as obvious when compared to the previous species of humans. These evolutions can be noticed in the gene sequence of modern humans. Some genes exhibit characteristics that are due to natural selection such as the ability to run fast or be afraid of seemingly harmless things. These characteristics or genes are not present in all humans but those who have them may pass them on to their offspring.
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References
National Academy of Sciences & Steering Committee on Science and Creationism. (1999). Science and Creationism: A View from the National Academy of Sciences, Second Edition (2nd ed.). National Academies Press. https://www.nap.edu/catalog/6024/science-and-creationism-a-view-from-the-national-academy-of
Tuttle, Russell Howard. "Human evolution". Encyclopedia Britannica, 12 Jan. 2021, https://www.britannica.com/science/human-evolution.
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