Evolutionary psychology as we shall see, is tightly bound up with culture. To understand the evolution of culture we need first to explain how we developed our big brain. Without increased brain power it’s unlikely that human culture would ever have developed beyond the level of modern chimpanzees.

Whilst there is good evidence that our species (& its forebears) evolved ever larger brains the question of why they did so is much harder to answer. We do know that it must have resulted from selection pressures and that the process involved pre-existing traits but that’s about all. So far as I can tell there is no definitive evidence to explain the exact process. However there are a number of possibilities.

The following is a ‘just so’ story. It’s not even the only such story that has been proposed. It is, however the one that seems most plausible to me. It’s a speculative explanation for the currently known facts. Those facts undoubtedly will be added to as time goes on. As our understanding increases our explanations will improve. That’s the scientific process. We haven’t reached the end of our journey of discovery. After all, it is only 2019.

What is culture?

In this context ‘culture’ means shared beliefs, rituals, understandings and explanations. That’s not rocket science. It would be hard to imagine any sizeable human group that didn’t have at least some cultural traits. The real question isn’t why humans developed culture but why (and how) our ancestors evolved the ability to do so in the first place. It seems that many changes were necessary to make human culture possible:

Selection pressures and adaptations

• Habitat changed (our ancestors became increasingly well adapted for life in the open and less well adapted for life among the trees;
• Brain volume increased significantly;
• Technology developed and changed (from basic ‘processed’ tools such as flint spear points and arrowheads to axes, jewellery and even boats);
• Hunting changed (there is evidence of much larger game animals being butchered as the species evolved).

These things must have resulted from selection pressures favouring individuals best suited to cope with change. Collectively they represented significant advantages to those individuals who possessed even some, if not all of the necessary adaptations. The gene pool was changing.

It seems to me (at least at this early stage of my studies) that the most important selection pressures were:

• Group size;
• Communication and language needs;
• Need for larger amounts of food;
• Need for cooperation to sustain large groups;
• Need for co-operation to ensure the survival of larger groups;
• Need to develop shared ‘memes’ to facilitate cooperation;
• Need to develop explanations to foster group cohesion (and ‘out-group’ alienation).

Many of the ‘mental modules’ we’ll discuss later in the series are refined versions of adaptations resulting from these very pressures.

Existing traits available for natural selection via directional and sexual adaptative pressures seem likely to have included…

Rudimentary communication via mating ‘songs’ & dance

Studies of our closest genetic relatives, chimpanzees and bonobos show a tendency to communicate via a range of sounds and gestures – especially during courtship. Gibbons which pair for life advertise their relationships to others via song and studies have shown that they also have different calls (rudimentary language) representing different kinds of threat.

All these things represent viable precursors of language. Assuming, as seems likely, that similair abilities were present in our early hominim ancestors, we have the raw material for natural selection to work with.

But there’s a problem. For sophisticated language to develop the animal would need a big brain. However to build a big brain the animal needs plentiful protein. Obtaining plentiful protein requires effective, co-operative hunting of big game. Co-operative hunting of big game requires communication which requires a big brain. Which came first, the chicken or the egg? Catch 22!

This was a major quandary for evolutionists for many years. It seemed as though big brain development was impossible and yet it happened. We have the fossils to prove it. What we didn’t have was an explanation. But now we have….

Theory of mind

Cooperation requires ‘Theory of mind’. That means an awareness of self and of others. It also requires an understanding that others may see things differently from ourselves. Without these two insights teamwork (and effective, cooperative big game hunting) would’ve been impossible for humans. And yet for years it was believed that no other primate species exhibited even rudimentary theory of mind. Until…………..…..

Co-operation and empathy

Another set of primate studies revealed not only significant theory of mind but also remarkable co-operation, especially related to aggression, dominant coalition and access to ‘mating rights’. Not only that, studies involving bonobos demonstrate significant empathy – another major requirement for the development of culture as we humans would recognise it. Once again we see the rudiments of another of the elements needed for big brain and cultural development. We can assume that our pre-human ancestors possessed the same rudimentary characteristics before the big brain developed.

So how might these elements come together? The process isn’t quite so complicated as it first appears.

As our ancestors left the forests and ventured out into the grasslands the need for effective warning systems became pressing. Natural selection (predation) favoured the best communicators creating a directional pressure toward more and more sophisticated language.

Improved language facilitates cooperation (largely based upon shared ‘memes’ or ‘explanations of the world’) which in turn facilitates more effective hunting.

More effective hunting meant more protein which allowed better brain development leading to even better communication.

Dependency and parental investment

The mechanics of childbirth provided a new problem for the evolving apes. Bipedalism (walking upright) was necessary for survival out of the woodlands but it meant a narrow birth canal. That means that bipedal hominims need to be born before their brains are fully developed. Otherwise their heads will be too large for the birthing process. This results in extended periods of helplessness for newborns (a characteristic that exists in humans to this day). This creates a serious selection pressure. Only those babies that are well looked after survive.

This explains why, compared with most other primates, human males invest far more of their time, energy and resources in providing for and nurturing their young. Chimpanzee males, our closest relatives typically don’t even know which offspring are theirs. Human males generally do – and they participate. We are a ‘High Male Parental Investment’ (MPI) species.

The extended helplessness of human infants created a significant selection pressure. Empathic and co-operative males provided the best nutrition and protection. Females that selected effective providers and nurturers as mates were most likely to see their young make it to maturity and produce offspring of their own. Their genes will survive.

Consequently males and females are subject to directional and sexual selective pressure favouring empathy, high parental investment and cooperation. This selection pressure (over many generations) imbued our ancestors with the ingredients for social culture and the means to fuel a big brain. The big brain in turn built upon these qualities to facilitate even greater technologies, communication and social interaction. This remarkable combination of selection pressures and adaptations allowed our species to develop, step by step from small bands of hunter gatherers into the large societies with sophisticated cultures that we know today