The Human Species
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| A group of people in Dhaka, Bangladesh (Steve Evans via Wikimedia Commons). |
When we look at the mirror on a particularly philosophical day, we may be compelled to ask questions beyond, “How do I look?” Lost in curiosity, we may wonder, for example, how we got here (both biologically and sociologically), or how our physical and emotional traits made it possible for us to establish complex societies. So, as curious individuals staring at the mirror on this early morning, contemplating ourselves, may we ask: Where did we come from? How did we develop highly organized societies and civilizations? What species are we related to? What made us different from our ape relatives and ancestors? What traits about us are most unique (and, perhaps, advantageous)? Let us now consider these questions in an overview of the modern human species–of ourselves.
An overview of the Homo sapien
The Homo sapien is the only extant (not extinct) species in the genus of Homo. Highly intelligent and walking on two legs, humans are known to form highly sophisticated societies, technologies and medicines; as is known now, humans are the first species to depart from the nomadic lifestyle to a largely sedentary and “built-up” lifestyle. Biologically, humans are part of the family Hominidae: the “Great Apes.” Hominidae originally included just the genus Homo, but now includes Pongo (orangutans), Gorilla (gorillas), and Pan (chimpanzees), all of which contain species that are at least 95% genetically identical to modern humans.
Human origins
Before we consider the origin of the human species, let us first look into the origins of both the primates and the Hominids.
Primates as a whole are much older than the Hominids or the Great Apes. The earliest primates arose approximately fifty-five million years ago alongside many other mammalian orders–such as the order carnivora. The earliest primates lived during the Eocene Epoch, an epoch that lasted from 55.8 to 33.9 million years ago. Because the continents are arranged much differently now than they were almost sixty million years ago, it is difficult to point out an exact origin of early primates, but fossilized remains of the early primates have been found throughout North America, Europe, and Asia. It is believed that these mammals evolved in part because of increased oxygen in the atmosphere, which is known to foster further evolutionary development in larger species.* Beginning some thirty million years ago–near the beginning of the Oligocene Epoch–some early primates evolved into the first apes and monkeys in modern-day Africa.** Finally, in the Miocene Epoch, the first Hominids are believed to have evolved; these two million years of evolution occurred almost exclusively in Ethiopia and Kenya, particularly the Afar Desert.
The Afar Desert is also where the first ancestors of the Homo sapien evolved. The earliest such species evolved six million years ago, several million years after their Hominid ancestors first evolved. The humans were present only in Africa for several million more years, but some eventually migrated to Asia and Europe. There likely have been fifteen to twenty species in the genus Homo since so far, but most such species had no living descendants. There is currently only one human species that remains alive to this day: the Homo sapien, otherwise known as the modern human. Modern humans first evolved in eastern Africa around 200,000 years ago; they were exceptionally nomadic, quickly crossing the savannas and the steppes in search of a better place and a new beginning. Around 33,000 years ago, for example, the Clovis people crossed the Bering Land Bridge, becoming the first Hominids to populate either of the continents. Ultimately, it was not until around only a few hundred years ago that contact had been established between Hominids of the Americas and the rest of the world.
Humans’ evolutionary tree
As humans are Hominids, they are most similar to their immediate relatives: namely orangutans, chimpanzees and gorillas. Of the ape species, those most similar to humans include chimpanzees and bonobos–a close relative of the chimpanzees–both of which share 98.7% of their DNA with humans. As such, it comes as no surprise that there are marked similarities between such species; as with humans, chimpanzees and bonobos are highly intelligent, and are among the most intelligent on the planet. The three species all have advanced tool-making abilities (chimpanzees and bonobos to a somewhat lesser extent than humans), highly intelligent and sophisticated communication, as well as complex and orderly societies. In many cases, chimpanzees and bonobos both are capable of achieving technological greatness. Indeed, it is possible that humans will not be the last intelligent species on the planet to arise.
Evolutionary anomalies in humans
To understand the many genetic and physical anomalies in humans, I read an article by LiveScience entitled the “Top Things That Make Humans Special.” Although I cringe at the idea that humans are “special,” the article nevertheless describes several interesting and exclusively human traits, all of which I thought I could elaborate on in this entry (as always, the article is cited in References).
One particularly effective and exclusively human possession is the larynx, otherwise known as the voice box. Occupying a large portion of the upper esophagus, the larynx evolved in submodern humans around 350,000 years ago. Unique to humans, it allowed for humans to articulate their communication into sounds and words, much unlike other hominids; without the larynx, we would not be able to speak in such language at all, let alone say words like indefatigable and transcendentalism. Note: The LiveScience article, which was published in 2011, did not (for obvious reasons) describe recent research proving that other Hominids, indeed, do have a larynx. In 2018, researchers discovered that humans’ unique ability to articulate was due, in part, to brain size, rather than the presence or absence of the larynx (see Dunn, Jacob C., et. al in References).
In addition, our means of movement are exclusive to us; whereas many of our ape relatives and ancestors utilize quadrupedal locomotion (movement with four limbs), humans rely on bipedal locomotion (movement with two limbs). Although we sacrificed quite a lot to move on two limbs, such an ability is nevertheless a superior physical trait. While humans are not as fast as many other animals, their more efficient center of gravity (and, therefore, less use of energy) allows humans to have an incredible level of endurance. When our ancestors wandered through the savannas and the steppes of Africa, we often won wars of attrition against our prey (if we did not already impale them with spears), chasing them until they had no more energy left to exert. Humans are by far the weakest of the Great Apes, yet they require more energy per unit mass than almost any other animal on the planet (blame our Ford F-150-hauling-its-maximum-weight-capacity brains for that); as such humans had to find unique means–namely tool-making and superior endurance–to fulfill their energy needs. Beyond endurance, it has been proven that humans could (theoretically) run up to forty miles per hour, even though the fastest living human can run only twenty-seven.
Humans are also the only species on Earth that blushes. It is still not understood why this is the case–and why, in particular, we are the only species to do so–but it is believed that the objective of such a gesture is to ensure honesty between members of human groups.
The last trait unique to humans is the post-reproduction age. Females of related species generally reproduce until they die, but such is not the case with humans; some human females in America, for example, often live upwards of thirty years after menopause. It is believed that such a trait results from a natural element of human societies: “the grandparent effect”; female grandparents may have been important to small bands of hunter-gatherers or even extended families because of their experience with raising children and because of their knowledge on survival, so they remained alive even beyond menopause.
From nomads to couch potatoes: a breakdown of the journey to civilization
Around 12,000 years ago and to a degree of simultaneity, small bands of hunter gatherers began to domesticate. The Neolithic Revolution, also considered the Agricultural Revolution, first occurred on the Fertile Crescent of the Middle East, and within 2,000 years, similar such revolutions had been achieved on every other inhabited continent in the world. It is believed that domestication began in many places independently because of a warming trend that began around 14,000 years ago. As conditions grew more favorable in the Fertile Crescent, wheat and barley began to grow naturally, and humans, as a result, began seeking to cultivate them further. As such, their efforts led them not only to the cultivation of agriculture, but to the fosterings of the sedentary lifestyle. Those pioneering humans established a short line of procession, which led them from hunting and gathering to small-scale gardening, and then to large fields of growth. As they achieved the last of these steps, they laid the groundwork for civilization.
Civilization can be attributed to the vast increase in food availability and yields that came with the Neolithic Revolution. The human population grew well beyond its carrying capacity, and ultimately began to grow exponentially as the fruits of agriculture led to industry, healthcare, technology, and transportation.
Indeed, the Neolithic Revolution was only the first of three agricultural revolutions; almost twelve-thousand years later, the Second Agricultural Revolution occurred concurrently with the Industrial Revolution, and almost two-hundred years after that, the Third Agricultural Revolution began near the end of the twentieth century.
Human sexuality and that of other species
(Please note that research on homosexuality in species other than humans, as with humans, is not robust, and is controversial due to its “human bias”–that is, approaching homosexual actions in other species through the lens of human homosexuality. As such, research is both ongoing and controversial, as the parameters of animal homosexuality are still subject to debate).
I found an interesting article likening human sexuality to sexuality in related species, and I thought I would create a section on broader human sexuality for this entry.*** The article, as with the several studies it mentioned, demonstrated that homosexuality and bisexuality is not confined merely to humans; while, verbatim, homosexuality is confined to merely humans and sheep, bisexuality is not. For example, female macaques often mate with one another, and while they never reproduce, they fulfill their desire of “social sex,” characteristic of humans and other apes. Other species such as black swans, penguins and bisons also participate in homosexual activities, often as a result of hormones.
Homosexuality in humans is, too, natural. For example, societies in which homosexuality is accepted have the same prevalence of homosexuality as those in which it is admonished. Humans crave social sex, and homosexuality is one of its purely natural exhibitions. There is no need to demean others because they are not like us; let us not judge books by their covers.
Wrapping it up
One species, borne by a small rock, orbiting an average star in an average galaxy, finding its way through a universe that is yet unknown to it. Even as it fights with itself and corrupts the conditions of the planet, the species is smart, innovative, cunning. Seventy-thousand years ago, its population fell to only a few thousand, rendering it on the verge of extinction. Yet it continued on. The species always began again. As they inch their toes into an ocean of new exploration, they must harness the courage and survival of their ancestors, straining to remember those who fought through hardship and established the new, profound journey the species faces, as it attempts, for the very first time, to save itself from itself.
Let this entry be a testament to the fact that there is so much we have yet to learn about ourselves, let alone the rest of the universe. The philosopher Socrates once said, “True wisdom comes to each of us when we realize how little we understand about life, ourselves, and the world around us.” We know only 5% of the oceans, 5% of the brain, and 0.00000000002368% of the universe.**** Yet our ignorance now can motivate us to persist through the darkness, towards the ever-growing light of science, and to quote another philosopher, Dr. Seuss, “The more that you read, the more things you will know. The more that you learn, the more places you'll go.” As always, take care and stay curious, everyone.
* A larger fauna was rodent-sized at the time, so “large” does not follow its present definition.
** Although the Oligocene is characterized by a gap in the primate fossil record, it is widely believed that old species of monkeys evolved during that epoch.
*** The original link (see References) now directs to BBC Earth, rather than to the article itself. The link in the References section, however, is correct, and I cannot find the article online (it has likely been deleted since this entry was first written).
**** The percentage of all knowledge that we know about both the universe and the brain are hypothetical estimates, not solid values.
References
2018. Neolithic Revolution - HISTORY. https://www.history.com/topics/pre-history/neolithic-revolution.
“Carnivora.” n.d. Wikipedia. Accessed January 26, 2023. https://en.wikipedia.org/wiki/Carnivora.
Dunn, Jacob C., and Jeroen B. Smaers. 2018. “Neural Correlates of Vocal Repertoire in Primates.” Frontiers in Neuroscience 12 (August). https://doi.org/10.3389/fnins.2018.00534.
“Eocene.” n.d. Wikipedia. Accessed January 26, 2023. https://en.wikipedia.org/wiki/Eocene.
Geggel, Laura, and Charles Q. Choi. 2022. “Top 10 things that make humans special.” Live Science. https://www.livescience.com/15689-evolution-human-special-species.html.
“Hominidae - great apes, humans | Wildlife Journal Junior.” n.d. New Hampshire PBS. Accessed January 26, 2023. https://nhpbs.org/wild/hominidae.asp.
“Human.” n.d. Wikipedia. Accessed January 26, 2023. https://en.wikipedia.org/wiki/Human.
“Introduction to Human Evolution | The Smithsonian Institution's Human Origins Program.” 2022. Smithsonian's Human Origins. https://humanorigins.si.edu/education/introduction-human-evolution.
“Oligocene.” n.d. Wikipedia. Accessed January 26, 2023. https://en.wikipedia.org/wiki/Oligocene.
O'Neil, Dennis. n.d. Early Primate Evolution: The First Primates. Accessed January 26, 2023. https://www2.palomar.edu/anthro/earlyprimates/early_2.htm.
Solly, Meilan. 2018. “Why Humans Are the Only Primates Capable of Talking.” Smithsonian Magazine. https://www.smithsonianmag.com/smart-news/why-are-humans-only-primates-capable-talking-180969968/.
Stringer, Chris. 2016. “The origin and evolution of Homo sapiens.” Philosophical Transactions of the Royal Society B 371, no. 1698 (July). https://doi.org/10.1098/rstb.2015.0237.
Ward, Carol V. 2015. “Chapter 10 - Australopithecines.” Basics in Human Evolution, 129-142. https://doi.org/10.1016/B978-0-12-802652-6.00010-4.
“When and where did our species originate? - The Australian Museum.” 2020. Australian Museum. https://australian.museum/learn/science/human-evolution/when-and-where-did-our-species-originate/.
Note: I switched to Chicago format for citations in order to avoid the "Accessed on" date, for such dates are inaccurate.
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