Is there such a thing as human nature?

It's not uncommon to hear "human nature" trucked out to explain all sorts of phenomena from war to human nurturing and cooperation. How scientifically valid are such claims? Is there such a thing as human nature? If so, what is it? In this episode of the P-Value, the first in our philosophy of biology season, we ask where there is a scientifically respectable notion of human nature?

Transcript

The P-Value Episode 2.1: Is there such a thing as human nature? 

Writing in the 3rd Century BCE, Chinese Confuscian philosopher, Xunzi (“Shun-ze”) argued that our inborn human nature is evil, selfish, anarchic and antisocial. It is, he claimed, culture, reflection, and conscious activity which makes us good. Without these things we are slaves to our own selfish desires. In short, in his view our human nature is something to be overcome or shaped. 

Not all Confuscian philosophers of the period held such a view, Mengze (“mungze”) or Mmencius disagreed. According to him, human nature is fundamentally good, which, like a sprouting plant, only requires the right environment to flourish. Our nature is in his view something we must nurture, rather than a burden to be overcome.

During the same period, Ancient Greek philosophers, Plato and Aristotle were offering remarkably similar views on human nature. Like Xunzi and Mengze, they also emphasised the essentiality of human nature. They postulated an intrinsic or immutable property or properties displayed by every human that were considered definitive of membership of humanity as a natural kind.

Although Aristotle, Plato, Xunzi and Mengze were writing over 2000 years ago, we see the same sorts of essentialist and normative views on human nature expressed today. Evolutionary psychologists such as Steven Pinker, for example, attribute a central explanatory role to human nature in understanding both our history and our future. According to Pinker our success as a species owes much to the role played by culture in mediating the impacts of our innate inner dispositions. Unlike Mengze and Xunzi’s views, Pinker emphasizes that there are both virtuous and less virtuous aspects of our psychology: our inner demons (such as our disposition to ideology, revenge and aggression) and our inner angels (such as reasoning, morality, empathy). Despite the obvious divergences from Xunzi and Mengze, Pinkers means of responding to our nature are remarkably similar. Our inner angels, he argues, must be nurtured, whilst our inner demons must be endured and overcome. Pinker is not alone. It is not unusual to hear aspects of human behaviour, from aggression and war to nurturing and motherhood, described as a matter of “human nature”.

What is “human nature” though? While it has intuitive appeal, is it something that has scientific rigor? How much store should we put in claims about human history and behaviour which rely heavily on the concept?

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Welcome to the P-value opening.

In this episode of the P-Value we explore the question “is there such a thing as human nature?”

Many philosophers of biology have responded to this question in the negative—human nature, they say, is nothing but a superstition and claims which rest on it are on shaky conceptual ground. It is, they say, an out-dated, folk notion without robust grounding in biological reality. 

Whilst we might take umbrage with the particulars of a view like Steven Pinker’s, the idea that there is nothing to human nature raises lots of challenges for everyday practice. The concept of “human nature” is at the heart of lots of normative discussions around moral value, personhood and blameworthiness. So, who is right? Is human nature bunk? Or is there something salvageable to the concept? 

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To assess the scientific merit of the idea of human nature, it is important to consider what we mean by the term in the first place. What is being claimed when we talk about “human nature”?

In the Western philosophical tradition, the idea that there is some special feature of humanity, some “essence” which makes us who we are has been very influential. What that essence is varies depending on the scholar. Kant picked out rationality. Christian thinkers point to a God-given soul. For Luther human nature rested on the capacity for private property. Setting aside those views reliant on some sort of supernatural basis for human nature, most naturalistic approaches share in common a commitment to essentialism. 

Essentialism is a claim about what it is that makes something it is, it’s metaphysics. For example, we might ask what is it that makes a piece of clay, a piece of clay, rather than a rock? Or a penguin, a penguin, rather than some other bird? Or a human, a human, rather than some other species. Knowing the answer to these questions helps us carve up the world into categories and is seen by many to be integral to many of our practices such as explanation and prediction.

For essentialists, the thing that makes something what it is, is, at least for natural kinds like species, a matter of having the right essence—an intrinsic feature or features. This essence is is typically thought to play two roles: one classificatory, and another explanatory. It is the intrinsic feature or features of an entity which are both definitive of membership of the kind of thing in question, and are the cause of the observable qualities characteristic of the kind. For example, in the case of a piece of gold we might say that the essence of goldness involves a certain type of arrangement of atoms. That arrangement is both definitive or classificatory of the kind—all and only those things which are gold have it—and it explains the special properties—the lustre, the hardness, the colour—of any piece of gold. 

In the history of Western thought, when people have talked about human nature they often have something like this sort of essence in mind—an innate property or properties—whether it be language, reason or consciousness—that are claimed to be uniquely necessary and sufficient to be human, and moreover, claimed to explain the special properties of members of the human kind, whether that be ecological domination, moral value or intelligence. Let’s call this the essentialist view of human nature. 

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In the 1980s philosophers such as David Hull and Michael Ghiselin drew on the empirical literature on biological species and debates about the nature of species as kinds, to argue that human nature is but a superstition. Specifically, they argue that at very least we cannot read off some empirically or scientifically respectable notion of human nature from how biologists divide up the living world into species. Essentialism about human nature is, they say, in conflict with evolutionary biology because it is not possible for evolution to produce a situation in which a species displays a universal, immutable, innate property which is also unique (and thus able to define species membership). Let’s call this the Taxonomic objection against human nature.

The Taxonomic objection against human nature derives from a more general critique of essentialism about biological species showing that essentialism conflicts with key aspects of Darwin’s theory of evolution by natural selection. Assuming human nature is a matter of cashing out what it is to be a member of the human species, they say, then it cannot be essentialist. 

The first reason they offer is that essentialism about species is in conflict with the ubiquity of variation within naturally evolving systems. As Darwin famously pointed out, evolution by natural selection occurs when we have three conditions met—offspring must resemble their parents, there must be variation in the traits that members of populations have, and that variation must result in differential survival and reproduction of individuals. Ultimately, when we have those three conditions met, we see change in the traits within populations over time. Genetic mutation, recombination and drift are the fundamental sources of such variation and they are ubiquitous to life. To return to humans, what this means is that even in the unlikely case that there was a really strong selective pressure on our species which resulted in some trait becoming a complete universal, the ubiquitous forces of mutation, recombination and drift would inevitably result in variation. So, even in the unlikely case that all and every human did have some universal trait, it would be a fragile and unusual state of affairs which would not persist. In this, universal traits or properties are a poor basis for species membership (unless we want species to be much more fine grained things than they are scientifically taken to be), and also seem a poor basis for something as socially significant as human nature is taken to be.

 A second way essentialism conflicts with Darwinian evolutionary biology is in its expectation that variation between species will be discontinuous. It is fairly universally agreed that there is just one tree of life. These shared origins means that we share many genes and traits, even with quite distant species. Furthermore, common environments see evolution generate similar solutions to the same problems across even quite distant taxa–consider for example the streamlined shape of sharks and dolphins. This again pushes against the idea that there could be some unique property or properties that only humans have and no other species could have. Not only is it unlikely that we would see a trait that all members of a species hold universally, but also it is unlikely that were such a trait to arise that it would be entirely discontinuous with all other traits in the tree of life. Species have fuzzy boundaries and so too will humanity, so the argument goes. 

It is worth noting that the one tree of life argument here, does not entirely rule out the possibility of a uniquely human trait—indeed, the long history of scientists looking for the big difference between us and other apes, from language to fire to rationality, suggests that for many scientists it is a live possibility. It is important however to be aware that essentialism about human nature requires that to be a member of the human species you must have that unique trait. Thus, when we look at many of the more plausibly unique human traits such as language and rationality, the essentialist account has the unpalatable and counter intuitive result that many people—those unable to speak, the very young and the very old—would fail to be members of humanity. This seems a very bad consequence indeed and one we should wish to avoid at all costs.

The realisation that essentialism is incompatible with evolutionary theory, has seen philosophers and scientists discard the idea that what makes a particular organism a member of a particular species is its unique essence. Instead, we have to look elsewhere for species membership. One popular view is that species are simply genealogical lineages. Membership of a species is simply membership of a particular historical lineage rather than the presence of a particular set of properties and thus species are essentially vague entities. This means that from a biological perspective to be human means simply to be part of the lineage of Homo sapiens, rather than having any particular properties. Thus, so say the advocates of the taxonomic case, biological species don’t offer us a respectable route to an essentialist account of human nature.

 The sense that we have a unique or special set of properties which make us human in someway is, on this view, but an illusion, partly borne out of the fact that many of our closest relatives, Neanderthals, the Denisovans, the Australopithecines, are extinct. Where they around today we would see that the boundaries between our lineage and others is as vague as the boundaries between many other species and their closest relatives. 

Not all agree with the conclusion Hull and Ghiselin draw from the taxonomic objection though. In the fifty years since they published their critiques of human nature, various philosophers have tried to revive or save human nature from the conceptual scrapheap. We shall turn to this next. 

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In his 2008 article “A plea for human nature” philosopher of cognitive science, Edouard Machery, argues that whilst Hull and Ghiselin are right to advocate the abandonment of essentialist approaches to human nature on taxonomic grounds, there is an alternative approach to human nature available to us which is compatible with modern evolutionary biology. 

Machery argues that rather than seeing necessary and jointly sufficient properties for humanity, human nature is better understood as being composed of the properties humans tend to possess as a result of the evolution of their species. Just like an ornithologist or herpetologist putting together a field guide of bird or snake species defines them via their typical observable properties, we can, says Machery, do the same for humanity. Human nature on this nomological or field guide account is thus a matter of picking out the properties humans tend to possess such as bipedalism, biparental investment and language. 

Significantly, this view turns on its head the usual relationship between human nature and explanations. On the essentialist approach, it is our essential human nature which underwrites various generalisations about humanity such as “all humans are selfish at heart” or “all humans are nurturing”. In contrast, on the field guide view of human nature, human nature doesn’t explain the generalisations, it is a mere summary of those generalisations which can then be used for various empirical purposes such as prediction and explanation.

This flipping on the head of the typical essentialist picture, allows the fieldguide view to avoid the taxonomic critique as it does not posit any immutable, unique, or universal human properties, merely typical properties. So, whilst language might be taken to be a part of human nature—it is after all the sort of thing an alien naturalist landing on our planet would surely put into the field-guide of Earth’s species as one of the human species characteristic traits—membership of the species doesn’t require language. Similarly, that other species might share characters with humans is fine, so long as there is some cluster of traits which can be used to reasonably reliably delineate us from other species. Membership of the species comes down to historical lineage (or some other species concept). 

In this sense Machery’s approach decouples human nature from our biological species concept, whilst also offering a naturalistic and, he says, valuable notion of human nature that can be used in science. It is a notion that can warrant generalisations about humans and what humans tend to be like such as the generalisations used in thinking about typical human behaviours in psychology. 

One worry we might have is that this view is overly profligate. There are many things many if not all humans share, for example, “a belief that water is wet” but they don’t seem like the right kind of thing to put in the human nature basket. Human nature seems to require properties which are not merely accidental or external in origin and this belief seems more like that. We might try to look to evolution to avoid this conclusion—only properties that are causally the product of natural selection are relevant to human nature— but we can reasonably produce some causal chain for “the belief water is wet” (or indeed any belief) with evolution in it because our belief making faculties themselves arose through evolution. 

Machery says whilst this much is true, what we must focus on is those traits which are the direct product of evolutionary processes. My belief that water is wet might indirectly be due to selection for a belief-making cognitive apparatus but the belief itself has not got an evolutionary history. It has not been subject to selection, nor has persisted and been inherited across generations in the right way. Something like language, in contrast, is the product of an evolutionary history. 

Whether or not Machery’s approach really saves human nature is debated. This is just the tip of the iceberg. If you want to learn more, I recommend checking out Elisabeth Hannon and Tim Lewens edited volume “Why we disagree about human nature” or Grant Ramsey’s newly released Cambridge Element “Human nature”.

That’s it for the P-Value for this week. I will be back next week thinking about genes and whether your genes make you who you are. 

Bye for now.