Who are we? How did we get to be this way? These are two of the greatest questions facing our species. The answers are still emerging after decades of field research in linguistics and anthropology, evolutionary theory, psychology, and neuroscience. But one thing is clear. Humans act, think, and exist according to the parameters of the dark matter of their minds – the things that they do not know that they know – their "unknown knowns" to shamelessly appropriate the words of Donald Rumsfeld.

All scientists believe that at some level evolution is responsible for how we humans got to be the way we are. But evolutionary theory alone is not enough. While superficially, humans are alike in many ways, at the same time, we are a varied species, with enormous differences separating individuals even within the same cultures, shaped in profound ways by our life experiences.

The question that most interests me is whether evolution structured humans to be flexible or rigid in their behavioural connection to their environment. The belief in rigidity is evident in a variety of theories, from Noam Chomsky's universal grammar (all humans are born with the same core grammar), to E.O. Wilson's sociobiology (human behaviour is the result of organic evolution), to evolutionary psychology (evolution has created massively modular minds), among whose major proponents are John Tooby, Leda Cosmides, Steven Pinker and others. The rigidity hypothesis is ultimately the idea that all humans are born with shared universal knowledge. This hypothesis traces back to Plato and is further seen in the work of Descartes, Freud, Jung and many others.

Cognitive flexibility, the idea that humans are not born with shared universal knowledge, traces back to Aristotle and is seen in the work of Hume, Berkeley, Locke, Edward Sapir and many others. It is frequently claimed that Immanuel Kant bridged the gap between these two very different modes of thought about the human condition, but I believe that his work falls with a thud on the side of the believers in human cognitive rigidity. These days, for reasons difficult to fathom, the rigidity hypothesis is in vogue.

My own view is that humans are clearly a mixture of hard-wired, rigid neural limitations and abilities along with tremendous cognitive flexibility. For example, in their brilliant book, The Archaelogy of Mind: Neuroevolutionary Origins of Human Emotions, Jaak Panksepp and Lucy Biven make a compelling case that human emotions are deeply embedded into the vertebrate brain via millions of years of evolution. At the same time, they acknowledge that the ability to learn from, interpret, and be empowered by emotions is hugely flexible within and across species. Crucially, however, Panksepp and Biven point out in their book that evidence for hard-wiring above the cerebellum, in the cortex – arguably the seat of our creativity and the engine of our minds – is at best negligible.

The flexibility line of thought finds support in modern understandings of culture and apperception. To understand the significance of culture in shaping human beings, let's first define it:

"'Culture' is an abstract network shaping and connecting social roles, hierarchically structured knowledge domains, and ranked values manifested by individuals. It is dynamic and ever-changing, from person to person.

To give an example of just one of the components of culture, consider values and their ranking. Suppose two cultures value wealth and honesty simultaneously. But suppose as well that they rank them ('>>' means 'more important than') this way:

Wealth >> Honesty vs. Honesty >> Wealth

This different ranking means that even cultures which hold the same values can produce very different behaviours depending on how they rank those values. The child will learn to interpret their experiences and to set their goals based in large part on the ranked values that are demonstrated to them, talked about, and rewarded. These values and their rankings are shared as languages are acquired, by children constructing their identities as part of their caregivers' community.

Alongside this view of culture, in my recent work I make the case that "self" emerges, as both Leibniz and the Buddha would have claimed, from the sum total of my experiences, interpreted via my cultural values, along with my individual interpretations of those values. The self is the remembered series of apperceptions. And human nature is the union of apperceptive memories and values – the latter being further analysed into biological values (thirst, hunger, health) and cultural values (family, body shape, types of intelligence, and so on).

In this model, humans and cultures are both flexible. There is no need to appeal to a form of biologically-programmed rigidity à la evolutionary psychology to account for similarities between societies. Those result from the need to cope with a similar world and similar biologies. I refer to this model as "dark matter of the mind" – the acquisition and maintenance of