Humanity and humans as we know them today have evolved considerably since the day the universe created them. Those changes have helped us adapt to the modern-day environment. Our predecessors looked very different from us; they had short arms with long legs and sharp teeth with bodies covered in hair (some would even go as far as calling them monsters!), and those features helped them survive back in their day. I don’t think modern-day humans can survive a day in the primitive era environment. We wouldn’t stand a chance in the freezing cold with this thin and soft skin of ours and without our fully automated warming and cooling systems- not to mention we’d starve to death without our supermarkets and fast-food restaurants.
Our vast universe
Life in this universe started billions of years before humans came into existence. As a matter of fact, if the Earth’s life was represented by a 24-hour clock, humanity would have occurred in the last one minute and 17 seconds of those 24 hours! Theories regarding the beginning of the universe vary remarkably, from the Big Bang Theory to the Steady State Theory. And even after the universe was born, the earth and the solar system we know today, came ages and ages after that.
But the proven scientific reason for the beginning of life and living things is still unknown. There are hundreds of different theories that people believe in. Some are considered unnatural/unbelievable, but cannot be disproved because there isn’t any evidence for or against them.
The Miller-Urey Experiment
One of the most widely-believed theories on chemicals’ origin, where inorganic substances were made into organic substances which are really important for life, comes from the Miller-Urey experiment. The Miller-Urey experiment simulated the hypothetical conditions present on early Earth to test what kind of environment would be needed for the birth of life. It was conducted in 1953 by Stanley L. Miller and Harold C. Urey at the University of Chicago.
The experiment used recreated the Earth’s early atmosphere with materials that were believed to make up its major components- water (H2O), methane (CH4), ammonia (NH3) and hydrogen (H2). The compounds were all sealed and circulated inside a sterile array of glass tubes and flasks connected to one another, with one flask half-full of water and another flask containing a pair of electrodes. The water was heated to add water vapour to the chemical mixture, simulating the Earth’s atmosphere. The flask with heated water represents water on the Earth’s surface, while the water vapour mimics the water that evaporates from lakes and seas before going into the atmosphere and forming rain. Sparks were fired between the flasks to simulate lightning storms (believed to be common on the early Earth) through the water vapours, and then the vapours cooled and condensed, which resulted in water (simulating the oceans) and this represented the first continuous water cycle.
At the end of one week of continuous operation, Miller and Urey observed by analysing the cooled water, 10-15% of the carbon within the system was now in the form of organic compounds. Two percent of the carbon had formed amino acids, including 13 of the 22 that are used to make proteins in living cells, with glycine as the most abundant.
The molecules produced were simple organic molecules, far from a complete living biochemical system, but the experiment established that the hypothetical processes could produce some building blocks of life without requiring life to synthesise them first. Although the discovery of amino acid formation was of tremendous significance in establishing that the raw materials of proteins were easy to obtain in a primitive earth environment, there remained a larger question as to the nature of the origin of genetic materials—in particular, the origin of DNA and RNA molecules.
Criticism of the Miller Urey Experiment
The experiment failed to explain how proteins were responsible for the formation of amino acids. A few scientists have contradicted that the gases used by Miller and Urey are not as abundant as shown in the experiment. They were of the notion that the gases released by volcanic eruptions, such as oxygen, nitrogen, and carbon dioxide, make up the atmosphere. Therefore, the results are not reliable.
After a glimpse of how life started on Earth, one of the most widely-held theories for the origin of humanity is Darwin’s Theory of Evolution, which holds the notion that all life is related and has descended from a common ancestor: birds and bananas, fishes and flowers- all related. Darwin’s general theory presumes the development of life from non-life and stresses a purely naturalistic descent with modification. That is, complex creatures evolve from more simplistic ancestors naturally over time. In a nutshell, as random genetic mutations occur within an organism’s genetic code, the beneficial mutations are preserved because they aid survival- a process known as the theory of natural selection by Charles Darwin, which describes the process by which organisms change over time as a result of changes in their heritable physical or behavioural traits. These changes allow an organism to better adapt to its environment, help it survive and have more offspring. It describes that humans come from a bigger family called the Hominidae, or the greater apes, which contains orangutans, gorillas, and chimps.
In the study of evolution, the hominoids (a member of the biological superfamily Hominoidea, including all modern apes, humans and a number of their extinct ancestors and relatives) are said to have split from the other apes starting with orangutans, about 14 million years ago, followed by gorillas about 8 million years ago, with the most recent split between chimpanzees and humans around 5 million years ago. They are called the ‘great apes’ because they are generally larger than other apes. But hominids are distinct from other apes, not only in their size but also in their high intelligence. The differences are presented in different ways. Apes are not fully bipedal like hominids. Another difference is that hominids also have a unique characteristic that shows pair bonding with another member and also having a home base, where apes lack that certain developmental trait. It has been shown that apes are not very good with food-sharing, while hominids have been shown to care and share food with other members of the group.
Hominids had several subfamilies including the Hominini, which consists of the Homo (humans) and Pan (chimpanzees and bonobos) but exclude the gorillas.
The Skull of a Hominoids
After splitting from the old apes, humans in their old shape evolved into 15 to 20 different species of early humans, such as the Ramapithecus (the first human ancestor). Scientists do not all agree, however, on how these species are related or which ones simply died out. Many early human species (certainly the majority of them) left no living descendants. Some clues reveal why some of our forebears were more successful than others. Several million years ago, when a great many hominin species lived side-by-side, they mainly ate plants. But as conditions changed, and hominins moved from the forests and trees to the drier open savannahs, they became increasingly carnivorous. The problem was the animals they hunted also had fewer plants to eat, so overall there was less food to go around. That competition drove some species to extinction.
Early humans migrated out of Africa into Asia probably 2 million years ago. They entered Europe somewhat later, between 1.5 and 1 million years.
The beginning of our transformation
Following the diversion of the other apes, a new ancestor of the modern-day human -the Ardipithecus ramidus- was found in the Afar Depression, now called Ethiopia. Ramidus was the most recent common ancestor of humans and chimpanzees. If we were to see a living ramidus individual, it would look very much like an ape walking on two legs. It had big toes adapted for locomotion in the trees and a slightly smaller brain size than a modern bonobo or a female common chimpanzee brain. Although there may have been a modest pattern of brain expansion over the first 4 million years of our evolution, it is becoming increasingly clear that significant brain expansion transcending the size seen in an ape did not occur in hominids until about 2 million years ago. In addition, examination of remains from several individuals suggests that ramidus was not very sexually dimorphic. Presumably, both males and females are represented in the sample, but they all seem to be about the same size. Their teeth lacked the specialisation of other apes, which suggested that it was a generalised omnivore and frugivore (fruit-eater) with a diet that did not depend heavily on foliage, fibrous plant material and hard or abrasive food. Its feet were better suited for walking than chimps.
A couple of million years later, Homos emerged and they were the first human-like creatures and consisted of two species, the Homo Erectus and Homo Neanderthalensis.
Homo neanderthalensis lived in Eurasia but went extinct about 40,000 years ago, most likely due to great climate change and diseases. On the other hand, Homo erectus appeared about two million years ago in several early migrations, spread throughout Africa and Eurasia. It is believed that they are the first human species to live in a hunter-gatherer society and control fire. About 500,000 years ago, this species, which was regarded as one of the most successful and adaptive species at that time, diverged into a new genus (Genus is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses, in biology).
Finally, Homo sapiens (modern humans) emerged from the Homo erectus, close to 300,000 to 200,000 years ago, most likely in Africa, then migrated to and populated most of the world. The spread of the large and increasing population of humans has profoundly affected the biosphere and millions of species worldwide. Among the key precedences that explain this evolutionary accomplishment is the presence of a substantial, well-developed brain, which permits progressive abstract reasoning, language, problem-solving, sociality and culture through social learning.
This theory of evolution is quite controversial because of the little evidence supporting it (which consists of skulls and bones), and because of other religious viewpoints suggesting that humans are clearly not considered animals and are classified in a group of their own.
Almost all of Charles Darwin’s data was based on anatomical evidence of various species. For instance, with Darwin’s finches, he noticed the beak size and shape was indicative of what kind of food the finches ate. Identical in every other way, the birds were clearly closely related but had the anatomical differences in their beaks that made them different species. These physical changes were necessary for the survival of the finches. Darwin noticed that the birds that did not have the right adaptations often died before they were able to reproduce. This led him to the idea of natural selection.
Darwin also had access to the fossil record. While there were not as many fossils in his time as ours, there was still plenty for Darwin to study and ponder over. The fossil record was able to clearly show how a species would change from an ancient form to a modern form through an accumulation of physical adaptations.
To help explain adaptations, Darwin turned to artificial selection as a way to experiment with his ideas of heredity. After he returned from his voyage on the HMS Beagle, Darwin went to work breeding pigeons. Using artificial selection, he chose traits he wanted the baby pigeons to express and bred the parents that showed those traits. He was able to show that artificially selected offspring showed desired traits more often than the general population. He used this information to explain how natural selection worked.
Arguments against Darwin’s theories
Still, there have always been substantial minorities who, whether on religious or other grounds, refuse to accept the Englishman’s ideas. Take the United States, long seen as a stronghold of ideas that challenge Darwin head-on (by insisting that the Biblical account of a six-day creation is literally true) or in a more indirect way, by insisting that the process of evolution must have been guided by some higher, intelligent power.
In Islam, according to the Quraan, humanity began when the first human, the Prophet Adam, was made from mud. He lived in heaven and was told by God to not eat an apple from a specific apple tree, and when he disobeyed, he was sent to Earth as a punishment. God created his wife Eve from his rib so they could continue the human race with their offspring.
However, in Buddhism, humans originated at the beginning of the current Kalpa (long period of time in Buddhist cosmology, generally between the creation and recreation of a world or universe) as deva-like (non-human creatures with godlike characteristics) beings. Those life forms shone with their own light and were capable of moving in air easily, living for eternities without desiring nutrition or any kind of sustenance. Over many years, they obtained a taste for physical nourishment, and became heftier and more like human beings; their appearances changed dramatically, and their lifespan shortened. Finally, they differentiated into two sexes and became sexually active.
Overall, no theory is 100% believed to be true and can be completely relied on. Perhaps with time, scientists will find more evidence about the origin of the whole universe and how we came to exist. Nevertheless, with a lot of controversial theories out there, it will always be a question for our minds.