grammer-schoolTheresa May wants to bring back grammar schools, there's a problem, and to explain what that problem is, consider us, Homo sapiens, and why segregation in any form goes against our nature.

We are social animals; we are designed to live in groups. Indeed, there is strong evidence that our brain developed the way it did to facilitate living in groups.

Anthropologist Robin Dunbar reckons that the optimal size for a group of humans is 148, they call it the Dunbar Number, the cognitive limit to how many people we can hold a stable relationship with.

And Dunbar reckons that speech evolved as a form of social grooming, holding together a community. This contrasts with other great apes which rely on traditional grooming for that purpose. Dunbar says that when we started to live in bigger groups we needed something else to promote group cohesion; so language evolved, and as it did the size of the groups we lived in grew too.

But in order to facilitate group living, evolution has hardwired certain characteristics into us. We tend to comply with the group, it's a rare individual who goes against accepted social norms. But this pressure to comply is so great that we can end up holding views and beliefs that may seem quite strange, even alien, to people from outside that group with a different culture. Sometimes the views that we develop from living in a group can even feel repugnant to outsiders.

Take an example of this, something called group polarisation. Studies show that if you put a group of mild risk takers together, then that group exaggerates this risk-taking tendency and a culture for reckless gambling emerges. The same applies, but in reverse, with a group made of people who are mildly risk averse, the group ends up paralysed with indecisiveness.

Groups exaggerate.

When you try to segregate children by ability, you are often segregating by ambition and drive, even though these characteristics can develop at different stages in a person’s development. So if you form a group of people who are all highly driven, focused on success and ambitious, then those characteristics become the overall driver of the group. Its culture creates an upwards spiral.

When you form a group of people who are less driven, and may even be made up of people who feel as if they have failed, the result can be a group mentality that frowns on excellence and celebrates a poor work ethic as applied to academic study.

People who may well have become quite capable of excelling in the future can become swept up in this cultural ethos, and can be held back from fulfilling potential, maybe forever.

There are different types of intelligence. Some people have oral skills and can talk persuasively, but are incapable of expressing their ideas in a written form. For some, it is the opposite. Some people are more empathetic, others more logical in their reasoning.

All these skills are important, but if grammar schools end up lumping people together who have certain characteristics the end result can be disastrous for both groups, starving each of diversity in attitudes, beliefs and skill types, creating one group: the achievers, who may become locked into a narrow mindset and become out of touch with wider society; while those who fail to get into the grammar school group can be locked into an attitude of self-fulfilling low expectations, and will, in any case, be robbed of the opportunity of gaining what Malcolm Gladwell calls 10,000 hours of experience that is so critical for success.

Not only would the re-introduction of the grammar school system be disastrous for those who do not get into grammar schools, especially late developers who are denied the chance of fulfilling potential, but it may even have a negative impact on those who go to grammar school.

Both society and the economy would be poorer. If anything, we need greater exposure to different ideas, beliefs and attitudes at schools, not less.