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What It Means to Be a Human

Humans are surprisingly difficult to pin down as an evolved species.

From Darwin onwards, scholars struggled to define our species. There are two leading theories but neither seems workable. One sees human psychology as shaped by evolution and stuck in the past. The other defines us as a cultural species who learn how to be human from scratch.

The Evolutionary Psychology Approach

Evolutionary psychologists claim that people living in all societies behave similarly and emphasize genetic causes for this. Men are more interested in casual sex, more physically aggressive, and more willing to take risks compared to women, for instance. Likewise,jealousy is a leading cause of spousal homicides everywhere and young adults are perceived as most sexually attractive.

From an observational perspective, such claims ring true. Accounting for them is more problematic. Evolutionary psychologists asserted that, during our more than two million year history, we became adapted to a hunter-gatherer way of life that favored such behavioral, and psychological, attributes. Genes that predisposed us to such traits were favored by natural selection.

But developmental genetics does not support this: genes cannot encode behavioral or psychological programs (1).

We must also bear in mind that the environment changed dramatically many times over the past two million years, in terms of climate, subsistence economy, and social structure. Moreover, ancestral humans were very different in terms of body size, brain size, anatomy, and thermal physiology, not to mention breeding system and social complexity.

Humans encompassed many different species, including Australopiths (i. e., “ape men” like fossil Lucy), Homo habilis, Homo erectus, Homo sapiens, and the many dead-end species still being discovered. The “environment of evolutionary adaptedness” is a tall tale because each species encountered varied environments.

If evolutionary psychologists focus on supposed adaptations to past conditions, cultural determinists define human beings in terms of information that is received via social learning in the lifetime of the individual.

The All-Cultural (Blank Slate) Approach

To a cultural determinist, we are defined not by our genetic heritage but by what we learn as members of a community. Examples include languages, religions, subsistence practices, and tool manufacture. This approach to defining humanity is also problematic.

If socially learned information defines us, what is information? Is it the verbal response to some item on a questionnaire, such as, “I approve of premarital sex”? Or. does it consist of changes in our brain cells that take place when such information is acquired? Or, is it a packet of information that is capable of being replicated? Theorists have not been able to nail down a definition that inspires widespread consensus.

Factually speaking, social learning is not peculiar to humans. Indeed, social learning is probably a feature of all social vertebrates (2).

Perhaps for this reason, anthropologists insist upon the cumulative quality of human social learning as our defining feature.

The argument is that human societies contain much more information than can be mastered by any one individual (3). This point is underlined by the information age where the volume of data is increasing at a phenomenal rate but it has not always been true.

In simpler societies, individuals can actually master most of the technological expertise, and other transmissible knowledge in their society. Moreover, historical study of artifacts, such as arrowheads, finds that their designs are transmitted across generations, rather than being spread horizontally across populations (or “diffused” 4). This means that cumulation of social knowledge is quite recent, most likely arising after the Agricultural Revolution.

So if we want to define humans as unique in having cumulative socially learned information, we would have to exclude most hunter gatherers from the category of humanity.

The main scientific problem with the cultural species approach is that it sets humans apart from the natural world by claiming that we are shaped by a specific society rather than by natural selection. Evolutionary psychologists argue that although mismatched to our current environments, we are adapted to a (fictitiously uniform) ancestral one.

Presented with two bad alternatives for defining our place in the natural world, it is reasonable to look for a better alternative, namely that humans, like all other species, are adapted to their current environment.

A Species Well Adapted to Modern Conditions?

There are many different ways in which animals become adapted to their current environments but evolutionists over-emphasize genetics because this fits most easily with Darwinian theory. Research suggests that genetic determinism has little to do with complex behavior although there are certainly genetic effects on temperament and personality.

Even simple adaptive behaviors are not genetically transmitted. Moose do not come into the world being afraid of wolves, their natural predator – they have to learn this, from their mothers and from experiences (4).

Even if one restricts the focus to genes, humans (and other species) can become adapted to varied local conditions with remarkable rapidity. One intriguing example involves alcohol intolerance in people from rice-growing regions of Asia. With rice farming, it was all too easy to make large quantities of alcohol that posed a significant risk of alcoholism that was better resisted by individuals who were alcohol intolerant and therefore left more offspring (5). Then there is the evolution of lactose tolerant adults in places where dairy farming was widely practiced. Such changes occurred within the last 5,000 years or so.

The pace of human adaptation has been even more rapid since the industrial revolution. Some obvious differences include increased stature (by up to 20 %), rising IQ scores (about 30 points in developed countries), increased life expectancy at birth (by about 100 %), increased standard of living in terms of hours work needed for subsistence, and the decline of both marriage and fertility - to about a third of agricultural levels (6). Such changes are not due to gene selection, of course. Nor are they all beneficial (increases in allergic diseases, obesity, diabetes, etc.). Yet, all are a reaction to environmental change.

What it means to be human is very much of a moving target. Both the leading narratives are so far out of touch with reality that they look like badly scripted science fiction movies. We need to investigate adaptation to contemporary conditions – and go beyond cultural, or genetic, determinism that explains little about what it means to be human.


1 Carroll. S. B. (2005). Endless forms most beautiful: The new science of evo devo and the making of the animal kingdom. New York: W. W. Norton.

2 Richerson, P. J., and Boyd, R. (2004). Not by genes alone: How culture transformed human evolution. Chicago: University of Chicago Press.

3 Mesoudi, A. (2011). Cultural evolution: How Darwinian theory can explain human culture and synthesize the social sciences. Chicago: University of Chicago Press.

4 Berger, J., Swenson, J. E., & Persson, I. L. (2001). Recolonizing carnivores and naïve prey: Conservation lessons from Pleistocene extinctions. Science, 291, 1036-1039.

5 Henrich, J. (2015). The secret of our success: How culture is driving human evolution domesticating our species and making us smarter. Princeton, NJ: Princeton university Press.

6 Floud, R., Fogel, R. W., Harris, B., & Hong, S. C. (2011). The changing body: Health, nutrition, and human development in the Western world since 1700. Cambridge, England: NBER/Cambridge University Press.