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Has Humankind Peaked?

John Paul is a recently retired academic with a background in psychology and philosophy.

Animal Painting - Caves of Lascaux

Animal Painting - Caves of Lascaux

In a previous article (Quester, 2017), I discussed some views variously claiming that we may be reaching the upper limits of our intellectual ability to solve fundamental problems in science, and in the knowledge domain more generally. Recent data from the physiological front are now taken by some researchers (e.g., Marck et al., 2017) to suggest that our species, Homo sapiens, is reaching its upper biological limits.

By jointly considering these seemingly converging contentions, we could gain a more comprehensive perspective on an issue of fundamental importance, which appears to have largely escaped the attention of the general public. Simply put, the question is whether our species has all but fulfilled its psycho-physical potential, and that, accordingly, the best we can hope for is to bring as many of us as possible to approximating this potential. By no means a modest ambition, given the state of the world; yet one that may not so subtly deflate our self-image and our grander hopes for the future of our species. But, read on.

The Thinker - Museum Rodin, Paris

The Thinker - Museum Rodin, Paris

Are We Banging Our Heads Against Cognitive Walls?

The lines of evidence I had surveyed in my article on the challenges crowding our cognitive horizon are well instantiated by the ‘hard problem of consciousness’, as philosopher David Chalmers (1995) aptly characterized the attempt to explain how ordinary physico-chemical processes within the brain can generate conscious mental states - such as the feeling of delight, or seeing the blue of the sky, or sensing the pain in a limb, etc. - which seem qualitatively different from these process. The explanatory gap between these two kinds of phenomena has proved extremely hard to close despite decades of sustained progress in the neurosciences. Many neuroscientists cling to the view that over time this seeming impassable chasm will be bridged as a result of the rapidly increasing understanding of brain activity. But this ‘promissory materialism’, as philosopher Karl Popper and Nobel laureate John Eccles felicitously dubbed it (1983), does no more than 'promise' that the mind will be ultimately ‘reduced’ to - that is fully explained by - purely physical processes.

This impasse has led over the years influential contemporary thinkers, including Colin McGinn, Steve Pinker, Noam Chomsky and others to propose that we may never conquer the problem of consciousness because its complexities exceed our cognitive resources. We share with all other animals the modalities of the evolutionary process. As such, our cognitive traits as mediated by the brain result from random genetic mutations and selective pressures. And, since all other species exhibit obvious cognitive limitations, there is no reason to exempt our own from being similarly constrained.

Noam Chomski articulated this position by proposing (Horgan1996/2015) that in science we ought to distinguish between ‘problems’ and ‘mysteries’. Problems can be solved; mysteries such as the origin and nature of consciousness are in principle unsolvable due to impassable cognitive limitations resulting from the brain’s evolutionary history, structure and function. No matter how hard it tries, a rat will never learn to negotiate a maze which requires it to turn left at every fork that corresponds to a progression of prime numbers. Our situation when contemplating some labyrinthine mysteries may be equally hopeless.

In a much discussed book, John Horgan (1996; 2015), argued that science as we know it may be approaching its end. He contends that the key discoveries in the natural sciences, from quantum mechanics and relativity in physics to evolution and the mechanisms of heredity in biology to name but a few, have been made once and for all. There is of course ample room for a more complete understanding of many phenomena in these domains; for the further accumulation of empirical data; and for the development of increasingly sophisticated technologies. But it is unlikely, Horgan argues, that these key theories will be superseded by radically new ones. Again, this does not mean that there are no problems left for science to study: far from it. But the deeper problems (Chomsky’s mysteries), such as the origin of life, the nature of consciousness, the source of natural laws, the question of whether or not there are multiple universes: these questions are most likely to remain unanswered because they exceed the theoretical, empirical, and technological grasp of our science. Creative scientists will never give up trying to solve these mysteries, as shown by an unending stream of ever more bewildering ideas about the physical world. But this kind of theorizing cannot be regarded as scientific: for the many competing theories proposed often cannot - either in principle or due to unmeetable technological challenges - be empirically tested. When addressing these most fundamental problems, science slides into philosophical territory. There, it can no longer establish truths; it merely bears witness to the uncertainties and limits of human knowledge.

Needless to say many scientists found this claim unacceptable, and quite simply false. But Horgan’s thesis should not be too hastily dismissed (Quester, 2017).

On the Flynn Effect: Is It Nearing Its End?

In that same article I looked for indications that such strictures could somehow be circumvented. This led me to the so called 'Flynn Effect' (e.g., Flynn, 1987), derived from studies of human intelligence as measured by psychometric tests.

The term refers to the significant growth over time in both main types of human intelligence: fluid (the ability to solve novel cognitive problems based upon one’s sheer intellectual ‘muscle’), and crystallized (the ability to effectively deploy one's knowledge, learned skills, and experience in one's life and work). Over the past one hundred years or so, a nearly linear increase in IQ has been observed in several Western countries. The duration of this effect is much too short to be explained in genetic terms. Rather, it appears to result largely from socio-cultural factors, including improvements in nutrition, education, health care, environmental stimulation, and decreasing family size.

The national average IQ of some developing countries is also increasing, similarly due to the improvement of the factors mentioned above. Accordingly, as more people worldwide gain access to advanced educational opportunities, one could expect that the number of supremely gifted well educated individuals capable of ground breaking discoveries will increase, thereby potentially leading to substantial scientific and intellectual progress.

Unfortunately, there are indications that the IQ growth in high income countries may be slowing dramatically, even reversing in some cases. For instance, Sundet and colleagues (2004) examining scores on intelligence tests administered to Norwegian conscripts between the 1950s and 2002, found that the increase of such scores stopped after the mid-1990s and actually declined in some subtests. Teasdale and Owen’s (2005) examination of IQ tests taken by Danish male conscripts revealed gains of about 3 points per decade between 1959 and 1979, of 2 points over the next two decades, of 1.3 over the following decade, and a decline of about 1.3 points between 1998 and 2004. A study by Flynn (2009) in the United Kingdom found that tests carried out in 2008 registered a loss of over two points relative to the 1980 results.

The reasons for these findings are highly complex, and deserve a correspondingly complex analysis. I merely point out here that this overall trend tallies with one based upon different kinds of human data, discussed in a recent paper by a number of French researchers (Marck et al., 2017).

The Dyscobulus of Myron, Roman bronze reduction. II Century AD

The Dyscobulus of Myron, Roman bronze reduction. II Century AD

Are We Reaching Our Biological Limits?

Marck and coworkers question whether Homo sapiens may have reached the limits of its potential. They did not address cognitive developments. They focused instead upon physiological measurements of human potential; more specifically, those related to lifespan, adult height, and maximal physiological performance, which collectively constitute excellent biological indicators of overall ability and potential.

The authors point out that the 20th century witnessed unequaled progress in humankind’s capabilities and performance. Whereas this is not in doubt, whether this progress may continue into the future - or whether we are fast approaching the upper limits of our capabilities as a natural species - is the subject of heated debate.

On the ‘progressive’ side of it, some researchers forecast that life expectancy may continue to grow indefinitely, at a rate of 2-3- years per decade (e.g., Oeppen and Vaupel, 2002); others speculate that scientific progress may eventually allow people to live indefinitely (e.g., De Grey, 2003). Regarding the upper limits of physical performance as manifested for instance in various sports, some researchers claim that we shall witness steadily improving performance records over the next few decades or even centuries. (e.g., Rozing et al ., 2017).

The proponents of this upbeat perspective rely on mathematical projections based upon existing long term trends, along with expectations of ongoing societal progress and mostly undefined yet substantial techno-scientific breakthroughs (yet another version of promissory claims).

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Other researchers, including Marck and coworkers (2017), take a different approach, by focusing - as Chomsky and others did on the cognitive side - upon the inescapable biological constraints that result from both environmental and evolutionary factors, to which Homo sapiens is subjected like all other animal species. From this basis, they move to empirically document their hypothesis that human limits may have been nearly reached.

They point out that muscles, bones, internal organs and cells are all subjected to clear limits in their structural and functional capabilities. For instance, cells can replicate only a finite number of times, and replication and aging bring about increasing damage which leads inevitably to their death; heart rate is anatomically and functionally limited in the maximum number of beats per minute it can achieve; more in general, every organ has a limited potential, heavily diminished by aging.

Along with organic limitations, the environment and the factors that determine the availability of its resources, including climatic change, played a powerful role in shaping human development over the course of its evolution.

In addition to physiological and environmental factors, societal efforts aimed at increasing the ability to exploit environmental resources played a decisive role in affecting human development, most notably within the short span of about the ten generations coeval with the industrial revolution. (e.g., Fogel, 2004). Unprecedented progress within the domains of energy production and utilization, nutrition, natural science, and the industrialization of the productive apparatus contributed to rapid changes in the profile of human populations, most notably within first world countries. These changes collectively led - among others - to increases in human height, longevity, and maximal physiological performance as measured by sports activities.

Using sport performance data to assess changes in human physiology provides highly accurate ways of measuring progress, especially based upon the data recorded from the Olympic games, which began in 1896. Marck and colleagues review an ample body of data, all of which show considerable progress throughout the 20th century (with the exception of the world war periods) in all so-called chronometric and metric sports, including running, swimming, weightlifting, skiing, and skating among others. A good example of this is the men marathon: the best time has decreased from 2 hours 55 minutes in 1908 to the current 2 hours and 2 minutes.

The factors that led to these dramatic increases in physiological performance were similarly at work in fostering a sizable increase in both life expectancy and maximal lifespan. Life expectancy at birth increased by about 30 years from 1900 to 2000 (e.g., Wilmoth, 2000) largely due to a reduction in infant mortality as a result of better medical practices, hygiene, vaccination etc.

As for gains in height, the 1896-1996 period saw an average increase of about 8 cm for both men and women.

However, recent data about the decades closest to the present point to a serious slow down in all such trends.

Sports such as track and field, cycling, skating, and weight lifting show evidence of plateauing over the past decades or so, for both sexes. In some cases, recent improvements may be due mostly to artificial means: to performance enhancing drugs - including hormones, steroids, and amphetamines - and to improvements in sport technology - from composite tennis rackets to LZR swimsuits to better racing surfaces, track suits and shoes -. Incidentally, recent data show that in Western Europe young men’s endurance and strength performance in physical tasks are declining.

As for life expectancy and lifespan, progress has slowed down considerably in high income countries, new gains resulting mostly from reduced mortality from cardiovascular disease and cancer. Over the past two decades, life expectancy has actually been declining somewhat in some sub populations in the United States, including American women of European descent. (e.g., Shiels et. al, 2017).

Maximal lifespan has increased over the past two centuries, but ever more slowly, and since 1997 no one has lived for more than 120 years. Marck and colleagues (2017) suggest that human longevity has plateaued at 115-120 years.

As for progress in physical height, after the conspicuous gains over the 1896-1996 period noted above, over the past 20 years or so the tallest populations among high income countries have shown no evidence of growth. Even among elite athletes, average height has plateaued; for instance, over the past 30 years the average height of NFL athletes has remained constant at 187 cm.

In sum, these data show that in the most recent decades notwithstanding further progress in nutrition, medicine, science and technology, the three traits discussed above have ceased to increase. It might be the case, therefore, that ‘modern societies have allowed our species to reach its limits. We are the first generations to become aware of these limitations’. (Marck et al, 2017, p.7).

If Marck's conclusion is correct, the cultural and social implications of this state of affairs are far reaching: the best our species can hope for is to bring the potential of individuals living in the less wealthy countries progressively close to the one more often enjoyed by high income countries; as for the latter, these societies should aim at keeping most of their citizens as close as possible to the upper limit of the species. An objective, incidentally, which could prove very difficult to reach, given the enormous stresses that overpopulation, massive resource depletion, large scale pollution and climate change are likely to posit for all world communities in the coming decades.

One may finally add that this sense of diminishing returns for our efforts seems also increasingly shared by many people in wealthy countries such as the United States, and is often embodied in the feeling, unexpected for North Americans, that the future of their children may not be as promising as the one they came to expect while growing up. But this stems largely from economic considerations, changes in the structure of the workforce and other sociological and technological developments that belong to a related though somewhat different order of considerations. Moreover, whereas many Westerners may be feeling - and to a degree experiencing - a measure of decline in their socioeconomic well being, other societies and nations, including colossi such as China and India may be undergoing opposite developmental trends.

The notion that humankind is rapidly approaching - or perhaps already has - the upper limits of its potential both cognitively and physiologically, is probably disturbing to many of us modern, who cherish the notion that, despite many drawbacks, we are destined for continuing progress. This notion was fostered by the faith in human reason and ability that characterized at least part of the Enlightenment, the broad philosophical and socio-political movement which powerfully shaped the modern era.

It is worth recalling in this connection that the ancient world mostly lacked such a view. Indeed, a common belief in the Greek-Roman world, as exemplified by the Greek Hesiod in his poem Works and Day, and by the Roman Ovid in his Metamorphoses, surmised that an originary golden age had been followed by eras of progressive decline and involution. An alternative view – rooted in a cyclical view of time and shared by many cultures: Greek and Babylonian, Eastern and Native American, posits that humanity goes through an endlessly repeating cycle of birth, growth, decline, and extinction.



Beyond Sapiens?

That’s it, then? Are we forever imprisoned within our biological limits?

As noted, yet another version of promissory materialism is being offered to counter this prospect. In its terms, the limit imposed by our biological evolution can be substantially transcended by cultural evolution, based principally upon the expectation of dramatic breakthroughs in biomedical science and technology.

A notable example of this viewpoint is the work of historian and futurist Yuval Noah Harari (2014), which has attracted the attention of the luminaries of Silicon Valley.

He concurs that Homo sapiens is subjected to severe biological constraints. But, he argues, this needs be the case no longer. Our species is on the verge of breaking through the strictures of natural evolution through what he calls ‘intelligent design’. The main tools through which this plan will come to fruition are biological engineering, cyborg engineering, and the engineering of inorganic life.

Biological engineering would rely extensively - though not solely – upon genetic engineering. Our growing ability to modify genes could result, in the more futuristic scenarios, in the creation of individuals with capabilities of various order which could vastly outpace those of our species, As he writes, "genetic engineering and other forms of biological engineering might enable us to make far reaching alterations not only to our physiology, immune system, and life expectancy, but also to our intellectual and emotional capacities." (2014, p.342).

Cyborg engineering would lead to beings that combine organic and inorganic parts, a foreshadowing of which is represented by the bionic ears and eyes currently under development.

The third way to change life is via the creation of entirely inorganic beings, an example of which is a component of the Human Brain Project - initiated in 2013 and financed by the European Union to the tune of hundreds of millions of euros - , which seeks to recreate a whole human brain in a computer by emulating through its electronic circuitry the complete neural networks that characterize this organ. If this project - reportedly in serious difficulties (Theil, 2015) - were met with success, this would mean, as Harari notes, that life, presumably including conscious life - would have broken away from its embodiment in the confining organic realm and into a more encompassing inorganic medium. This line of research if successful – a very big if – could lead to machines which could act, think, and talk like a human being. This in turn could be just the initial step in a new intelligently driven – whether by humans of by machines – evolutionary process whose outcomes are difficult to envisage.

Of course, as sagely noted by Yogi Berra, “'It's tough to make predictions, especially about the future”...

Needless to say, all these extraordinary developments may well never materialize – our limited cognitive abilities may well not permit it in the end –, or in much lesser dramatic fashion than envisioned in these scenarios. It is very instructive, in this regard, to go back to the beginning of artificial intelligence - several decades ago - and to review its pioneers' grandiose predictions and promises of then imminent breakthroughs, that many decades later are far from being approximated.

But let us assume that some at least of these revolutionary developments were to come to pass. Interestingly, there is a basic agreement between some of the ‘progressivists’, and those who are much less sanguine about a marvel filled future.

Whether you believe that Homo sapiens is about to reach its maximum potential and must rest content with staying close to that level; or trust instead that the science and technology it has spawned at the apex of its potential may lead to an altogether new variety of evolution, including that of the genus Homo: under both scenario, Sapiens has peaked. We may never be able to create something which exceeds our inherent limits. Or perhaps we will: but in the latter case, the new entities initially hatched by our ingenuity will be very different - for better or for worse - from us. Not only physically but also cognitively, and emotionally.

This latter scenario, therefore, is even more radically negative about the future of people like you and me: not only have we Sapiens peaked: we may eventually cease to exist. Or perhaps those who will refuse - or perhaps cannot afford - to change will be at best relegated to the role of a secondary, inferior species, a relic of the era of pre-intelligent evolution.

Would you want that?



Chalmers, D.J. (1995). Facing up to the Problem of Consciousness. Journal of Consciousness Studies, 2, 200-219.

de Grey, A. (2003). Foreseeable and more distant rejuvenation therapies. In Aging Intervention and Therapies, ed. SIS Rattan. 379-395. Singapore: World Scientific Publishers.

Flynn, J. R. (1987). Massive IQ Gains in 14 Nations: What IQ Tests Really Measure. Psychological Bulletin, 101 (2),171-191.

Flynn, J. R. (2009). What Is Intelligence: Beyond the Flynn Effect (expanded paperback ed.). Cambridge: Cambridge University Press.

Fogel, R. W. (2004). The Escape from Hunger and Premature Death, 1700-2100: Europe, America, and the Third World. New York: Cambridge University Press.

Harari, Y. H. (2014). Sapiens: A Brief History of Humankind. McClelland and Stewart.

Horgan, J. (1996/2015). The End of Science. Reading: Addison-Wesley.

Marck, A., Antero, J., Berthelot, G., Saulliere, G., Jancovici, J-M., Masson-Delmotte, V., Boeuf, G., Spedding, M., Le Bourg, E., Toussaint, J-F. (2017) Are we reaching the limits of Homo sapiens? Frontiers in Physiology, 8, 1-12.

Oeppen, J., and Vaupel, J. W. (2002). Broken limits to life expectancy. Science, 296, 1029-1031

Popper, K. R., and Eccles, J. C. (1983). The Self and its Brain. London: Routledge and K. Paul.

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Rozing, M. P., Kirkwood, T. B. L., and Westendorp, R. G. I. (2017). Is there evidence for a limit to human lifespan? Nature, 546, E11-E12.

Shiels, M. S., Chernyavskiy, P., Anderson, W. F., Best, A.F., Haozous, E. A., Hartge, P. (2017). Trends in premature mortality in the US by sex, race, and ethnicity from 1999 to 2014: an analysis of death certificate data. Lancet, 389, 1043-1054.

Sundet, J.; Barlaug, D.; Torjussen, T. (2004). The end of the Flynn effect?: A study of secular trends in mean intelligence test scores of Norwegian conscripts during half a century. Intelligence, 32, 349-362.

Teasdale, T.W., Owen D. R. (2005). A long-term rise and recent decline in intelligence test performance: The Flynn Effect in reverse". Personality and Individual Differences. 39(4), 837–843.

Theil, R. (2015).

© 2018 John Paul Quester


Camille Harris from SF Bay Area on January 20, 2018:

Thanks, Paul - you're right. I hadn't actually considered that. So, by that logic, two contemporaneous modern human species would be able to produce fertile offspring. Back to the drawing board...I may write an article about it. Thanks for the inspiration!

John Paul Quester (author) from North America on January 15, 2018:

Hi Camille,

Thanks for your questions. But I am not able to answer them. I will just note that - as you may already know - recent evidence shows that two different species of humans, Sapiens and Neanderthal, interbred. Indeed, most European and Asians carry about 2% of Neanderthal DNA.

Camille Harris from SF Bay Area on January 14, 2018:

Hi John,

Your article touches on a question I've been pondering for some time:

When will we KNOW (definitively) there's a species beyond Sapiens?

(How much genetic difference is required? Would it be the inability to produce fertile offspring from our pairing (Homo Sapiens + the new human species)?)

What do you think?

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