HAS HUMAN EVOLUTION COME TO AN END?

Is it true that we Hominids evolved for millions of years and then abruptly stopped? Let’s find out in this article.

Any academic book, research paper, documentary, or infographic including the keyword “timeline human evolution” might assist you in properly understanding the process of human evolution. The earliest primates appeared around 55 million years ago (55 MYA), then came the split of the ancestry of humans and chimps, gorillas 8–6 MYA, and our ancestors gradually evolved to walk on two feet. Lucy the southern ape died from tree falls around 3.2 million years ago. It took another megaannum or two for the first groups of hunter-gatherers migrated out of Africa. The practice of hunting with spears appeared around 400,000 years ago; and Neanderthals survived for another 205,000 years before ceasing to exist due to the emergence of our species — Homo-sapiens, which had expanded across Asia and Europe before arriving in the Americas 12,000 years ago. Finally, the Sumerians of Mesopotamia built the world’s first civilisation circa 4000 BC [1]. The rest is history as we know it, which has been perpetuated to this day.

Personally, I don’t want to devote the full length of today’s essay to delving into the minutiae of human evolutionary history, which can be found in better-structured evolutionary works. Instead, this essay is investigating the subject through the famed paleontologist Stephen Jay Gould’s claim in 2000: “There’s been no biological change in humans in 40,000 or 50,000 years. Everything we call culture and civilization we’ve built with the same body and brain” [2]. This assertion has stirred scepticism in the evolutionary research community, and expresses a widely held belief that human evolution has long come to an end. Indeed, humanity hasn’t evolved into any other form — humans have been humans since we were able to stand upright, to walk on two legs, to own intellectual property, to build society, and to develop modern civilization. Our situation is undoubtedly one of a kind on this planet. A bear confined in the frigid Arctic for millennia would evolve with thick fur to keep itself warm, but humans would light fire, make warm clothing, or construct boats and depart for a warmer climate. Scientists have every reason to believe that, given changes in an environment that symbolizes natural selection, humanity, with our knowledge and inventiveness, may have discovered a way to exist without biological evolution.

Is it true that we Hominids evolved for millions of years and then abruptly stopped? Can Stephen Jay Gould’s reputation reinforce his statement? Let’s find out in this article.

1. 1–0–1 evolution

Behind Gould’s conclusion that we have ceased to evolve lays a basic rationale: By the time the human lineage has acquired a brain of sufficient size and with sufficient intelligence to produce a sophisticated culture (which Gould points to the advent of agriculture 12,000 years ago [3]), biological evolution would be completely superseded by cultural evolution. In other words, humans would rely on culture and technology for survival rather than random selection and evolution mechanisms. The heart of this argument, culture, is then defined as shared and hereditary social practices that constitute a mechanism of abiotic adaptation beyond the body. It is therefore crucial in determining whether evolution still has any biological impact on humans. This nonetheless puts forward the question of when and where human culture originated. How did anatomically modern humans begin to express creative thinking and symbolic knowledge, becoming ‘fully human’ in both body and behaviors?

First, let’s rewind to the beginning of time, to the moment when the human-fire relation originated. Homo-erectus (upright man) is believed to have been the first to perceive and use fire [4], but how long did it take to attain the impulse that one should flee the fire or stay to save a friend trapped in it? This is a difficult undertaking for prehistoric people didn’t leave us any scribes; their traces were only unearthed in ancient sites. In essence, prehistory is the period before history was first scribed, whereas 99 percent of human stories date back to prehistory. American archaeologist Robert J. Braidwood believes that half a million years is tough to comprehend, even when we equate this entire era to a day: “The present time is midnight, and Jesus was born just five minutes and thirty-six seconds ago. Earliest history began less than fifteen minutes ago. Everything before 11:45 was in prehistoric time” [5].

Over time, Homo-erectus departed Africa and spread to Europe, Central Asia, Southwest Asia, South Asia, and China. Anthropologists believe that the invention of stone tools was a deciding element in early human migration. Previously, the global climate had gotten colder near the conclusion of the Tertiary period, then the cold extended into the Quaternary period, specifically the Ice Age. Despite its name, the climate throughout this time period was not consistently frigid, with warm intervals frequently interspersed with glacial times. However, the environmental changes were still rather abrupt, forcing every species to adapt or it’ll cease to exist. In response to these changes, Homo-erectus evolved a larger brain (about a quarter of today’s human brain size [6]) and became more intellect. This biological evolution enabled them to generate fire and to survive for another megaannum. There has been no archaeological evidence for personal ornaments such as necklaces, jewelry, or carvings during this time period; and so it is probable that Homo-erectus hadn’t transcended the so-called primordial instincts, remaining incapable of critical thinking.

70,000 years later, Europe saw the rapid evolution of Homo-neanderthalensis (Neanderthals). A huge number of fossil remains reveal that Neanderthals possessed short stature, a strong body, and a broad, rough nose that allowed them to live well and dominate in frigid regions by reducing body heat loss [7]. Several monuments have proved Neanderthals could utilize tools, care for the sick and elderly, and bury the deceased. Still, the ability to use tools is not necessarily a unique feature of humans, as other animals may use, or even build basic tools. Sea otters, for example, can use a rock to crack open abalone shells; chimps use a peeling tree limb to entice termites to attach and consume them, and even crack open nut shells by wooden hammers [8]. Neanderthals possessed brains that were around the same size as modern humans, but were rather huge for their body size, and were unable to construct symbolic things such as language or decorative goods. There have been numerous hypotheses to explain Neanderthal demise, including violent combats, disease infection from the huge invasion of Homo-sapiens, natural disasters, climatic change, and incest [9]. During their time on this planet, Neanderthal didn’t leave any trace of art-related activities, whilst symbolic thinking and language were trademarks of a more dominating species — Homo-sapiens.

After departing Africa (approximately 70,000 years ago), Homo-sapiens have brought about a behavioral revolution by becoming prevalent throughout the region and the rest of the planet, creating species consistency [10]. It is impossible to ascertain why they emigrated from Africa, perhaps due to the depletion of resources and food as the population grew rapidly. Given their language skills, humans could articulate their concerns and weigh the benefits and hazards of leaving or staying, allowing them to arrange organized migration at community level. According to a widely accepted migration theory, the Ice Age formed isthmuses joining continents, and Homo-sapiens traversed these bridges to spread over the planet [11]. Unlike its Hominid relatives, Homo-sapiens, the first modern human with a large brain and their own language [12], has been the only known species to have succeeded in migrating, adapting, and dramatically changing many parts of the world, exerting profound impacts on both the environment and the earth’s history. Language was invented as a result of great intellectual growth, giving modern humans the ability to think rationally and to make decisions based on reasoning rather than acting on pure instincts — as other animals do. This means that humans can now plan, solve issues, and organize populations more effectively.

2. When did humans become humans?

Profound cognitive capacities and abstract reasoning set modern humans apart from the rest of the living world. During the 1970s, archaeologists came to an agreement that the beginning of human civilization occurred around 40,000 years ago, after their migration to Europe. Based on the painted remains discovered in the Lascaux and Chauvet caves, they dubbed this a “creative explosion” [13]. This viewpoint, however, is thought to be the result of Europeanist dogma, and archaeologists were simply not looking for modern man’s creation elsewhere. Citing other sites in Africa dated from 70,000 to 100,000 years ago, opponents of this theory argue that Homo-sapiens must have laid the foundations for civilization far earlier. Uncertainty and disagreement regarding the roots of human culture appear to derive from the temporal ‘lag’ between human evolution and the emergence of modern thinking. The need for creativity may have arisen as a result of natural variability, environmental change, or competition from other species. Alternatively, “modern-like” behavioral capacities could have appeared later as the product of an unknown genetic variant.

Archaeologists discovered a rare abalone shell with a crimson interior while digging a cave off the coast of South Africa. Analyzing the mixture and neighboring rock, scientists realized they had discovered the world’s oldest known paint, produced around 100,000 years ago and consisting of charcoal, crushed animal bones, and an unknown liquid. It is likely that this shell served as a prehistoric paint jar [14]. This discovery exposes how long ago people employed paint, providing insight into early humans’ thoughts. The use of different materials to make a product that differs from the original form while leaving the recipe for the next ‘products’ demonstrated early humans had the ability to think abstractly, perceive awareness of innovation, and anticipate future plans at the time. This is one of the mental faculties that distinguish Homo-sapiens from other Hominid species. One issue, though, is determining when modern humans first developed modern awareness. To this day, it’s still a difficult undertaking to tell what level of perception one’s at. Cave paintings, jewelry, and sculptures may have been the first forms of human art some 40,000 years ago. However, as South African artefacts from between 70,000 and 164,000 years ago were discovered later, proof of this conduct became even more ancient. This way, the task of finding proof of the origins of current cognition becomes difficult if just the relics of old art are used. At this point, the answer to the question of when humans became humans appears to be significantly more complicated.

Archaeologist Thomas Wynn proposed in his 2012 study — “The Evolution of Working Memory” — that symbolic thoughts expressed in artifacts may not fully explain all changes in the human mind. Thus, he and his colleagues hypothesized that the determining factor representing the emergence of cognitive thinking is “working memory” [15]. In essence, working memory allows the brain to simultaneously access a relatively small amount of processed temporary information, a necessary step toward long-term memory where memories are stored. Working memory represents the ability to pay attention to something even when distracted, and it functions as a multitasking mechanism in strategizing, considering alternatives, and problem solving. This mechanism doesn’t require much effort; it operates on autopilot, akin to getting in your car and letting it take over. In essence, man-made tools dating back more than 70,000 years could have been created using short-term memory through repetitive honing — the only needed step. The most convincing evidence is nonetheless the archaeological remains of animal traps discovered at the Sibudu cave in South Africa, which demonstrates just humans organized hunts of a large number of mammals such as wild boar and antelope using traps [16]. A trap tells a lot about intelligence: it’s a device that can attract and capture the prey, and the hunter needs to return to reap the benefits. The use of traps during this period demonstrates humans, through working memory, came up with effective working mechanisms to aid them in planning, calculating possible solutions, and retaining necessary information. It turns out in addition to abstract thinking, language and the ability to deploy short-term memory might have facilitated advanced cognition. From there, a man could decide whether to flee the fire or return to save his friend, or even commit murder by starting the fire at the outset.

Together with fundamental advances in engineering tools, the ability to invent new technology in response to environmental changes has played a significant role in the global spread of Homo sapiens, setting us apart from all other Hominids. Culture, as a product of the human mind, has been an external means of human survival — a non-biological, non-hereditary, but learned and inherited behavior that has kept us alive for millennia and empowered humans to dominate this planet. Human culture is basically a collection of ideas and actions discovered, learned, and passed down through generations and expressed in language — the ‘private property’ of human. By creating gods, anticipating death, the future and the past, it’s got us to know our place in the food chain. The rapid cultural evolution — since the advent of advanced awareness and the introduction of agriculture 12,000 years ago — is what causes the environment to be damaged, modified, and colonized at will. After megaanna, it only took humans 12,000 years to evolve from spears to rockets, then to nuclear weapons within a few decades later. Facing competition, modern humans have used intrinsic cultural resources to maintain a common identity, transmit ideas, and form societies into long-term stable regional groups.

3. After all, has human evolution come to an end?

Archaeologists recently discovered fossil sites that show all modern humans have a common ancestor who lived around 200,000 years ago in Africa, thus having more genetic uniformity than most other animals on this planet. This is the main reason many people argue Homo-sapiens is the end of our biological evolution. British naturalist Sir David Attenborough agreed with Gould about the end of human evolution, suggesting that birth control has contributed to the halting of biological evolution. “We stopped natural selection as soon as we started being able to rear 90–95 percent of our babies that are born. We are the only species to have put a halt to natural selection” [17]. At the same time, he contends that preventing natural selection is not as important or as tragic as it seems, for humans can now ensure the species’ continued survival by promoting cultural evolution.

However, Dr Ian Rickard of Durham University, writing in The Guardian, disputed Attenborough’s claims, pointing out that birth control, even abortion, can’t end natural selection. Nonetheless, evolution would be ‘passed’ onto individuals who reproduce; in other words, DNA will still be passed onto the next generations. Natural selection, according to Ian, is not concerned with the survival of any species; it only requires variation from the dominant individuals in a population and will therefore persist one way or another [18]. Similarly, in their 2009 book “The 10,000 Year Explosion”, evolutionary biologists Gregory Cochran and Henry Harpend argued that “Human evolution has accelerated in the past 10,000 years, rather than slowing or stopping, and is now happening about 100 times faster than its long-term average over the 6 million years of our existence” [19].

One could argue that human evolution has come to a halt because we are now adapting to our environment through cultural evolution rather than biological evolution. From a medical standpoint, humans are no longer evolving to adapt to infectious diseases (plague, malaria, and HIV) as a part of natural selection. Rather, we’re adapting culturally with the inventions of vaccines, antibiotics, and medical regimens. According to this viewpoint, albeit having biological evolution halted, humans are still trapped in bodies that adapt only to prehistoric environments. As a result, human health is deteriorating in many ways. However, humans are not the only exception, as all other creatures can adapt to their surroundings, even in the absence of ontological culture. This way, the argument that biological evolution has been replaced by cultural evolution is very implausible.

Agriculture has evolved and been spread over the last 12,000 years — the most stable climate in history — and resulted in exponential population growth. Also, it has altered the density of people living in the same area since farmers often prefer to live close to the fields, resulting in a much less mobile lifestyle. These factors have since created an ideal environment for infectious diseases, which in turn breeds a more pronounced expression of natural selection in human evolution. Malaria, for example, is a rare disease originating in Africa’s virgin rainforests. However, areas with developed agriculture and dense population have made more people vulnerable to this disease than ever before. Over time, this has forced humans to adapt to malaria via natural selection.

Despite advances in modern medicine, infectious agents continue to play a significant role in driving biological evolution. As the human population grows, we’ve altered the environment by encroaching on and improving the habitats of other species, resulting in the emergence of more infectious diseases. Worse still, some cross-contamination agents have even adapted to their host, the human body. As evident as it seems, chickenpox, plague, malaria, measles, HIV, and other infectious diseases can’t be prevented or eliminated through cultural evolution. Rather, they have been the agents that promote biological evolution, allowing humans to adapt to themselves.

In addition, the fact that the human population has continued to grow rapidly since the invention of agriculture has increased the likelihood of mutations, genetic drift, and gene flow, knowing that not just natural selection, but all three of these factors can drive evolution. A small population will have very few mutations, but with the current world population of 7.9 billion people [20], the mutation rate is likely to occur in every generation. Simultaneously, a sharp increase in population would result in a weakening of genetic drift, while a series of civilizational innovations that allow humans to travel around the world would stimulate gene flow. Together, these two changes have boosted genetic variability in human populations. Scott Solomon, a biologist at the University of Texas at Austin, observed, sequenced genes, and discovered that natural-selection-induced changes in the human body have recently increased our tolerance to dietary changes, to ultraviolet radiation from the Sun, and to low oxygen densities in the highlands while aiding in the prevention of infectious diseases [21].

So, in the end, has evolution come to an end?

No, we have evolved and will continue to evolve. Extinction is the only thing that can truly halt the evolution of any organism. Evolution itself can be slowed down by reducing and maintaining population sizes so that most genetic variations are eliminated through genetic drift, and the occurrence of new mutations will drastically drop. As genetic variation is the root of all evolution, prolonging a population’s small size will severely weaken its ability to biologically evolve, but it will not be completely eliminated. This is nearly impossible for the human population is soaring, making the human gene pool a repository for a large amount of genetic variation. This way, our biological evolutionary potential will remain incredibly high.

Cultural evolution may occur much faster than biological evolution as individuals can change their behaviors without having to wait for reproduction or death. To redistribute the rate of variation, death occurs. Because biological evolution is genetic, it will occur vertically; meaning recognition will remain dependent on the reproductive cycle and the entire process can be slowed down. On the other hand, for cultural evolution can be learned and inherited, it manifests in a much more horizontal and widespread manner. After all, cultural evolution will not replace biological evolution; instead, it’ll aid humans in adapting to our surroundings.

As long as the population is reproducible, evolution will perpetuate. Human history will continue to be written unless evolution itself causes humanity’s destruction. If that’s the case, let’s hope that day never comes.

___________

References:

1. Mark Stanford, The Cultural Evolution of Human Nature.

2. Alan R. Templeton, Has Human Evolution Stopped?

References:

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