Feelings of attachment are the product of neurotransmitters such as serotonin and oxytocin in the brain.

The evolutionary history of the human brain can be seen in its three subsections.

The demystification of human emotions by science is not a recent thing. As early as 450 BC, the Western world’s first physician, Hippocrates, proposed that emotions – such as love – are a product of the brain.

Even though Hippocrates’ hypothesis turned out to be correct, it took more than 2000 years before scientists began to closely examine the brain and the effect it has on human behavior.

Today, thanks to the scientific discoveries of the past few decades, our knowledge of the brain has far exceeded that which even the prescient Hippocrates could have predicted.

One such discovery is that of how the human brain evolved over the millennia.

In order to survive, our ancestors had to adapt to their changing environments. This included changes in their brains, which helped them to survive in new climates and conditions.

For example, our distant ancestors were forced by climate change to move from the forest habitat to the dry savannah planes. In order to survive in this harsh environment, their brains had to adapt to out‑smart predators and find food. Gradually, step by step, adaptation by adaptation, our established brain structures were transformed.

What evidence do we have to support this theory?

The human brain’s evolutionary history can be found in its three subsections.

The oldest of these, the Reptilian Brain, sits at the top of the spinal cord and controls our most basic bodily functions and impulses.

Next is the Limbic Brain, situated around the reptilian brain. Here you can find such famous components as the amygdala, which plays a major role in the production of fear.

The development of the limbic brain has been crucial for the evolution of mammals. In contrast to reptiles, it enables them to feel attachment towards their young. As a result, mammals – unlike reptiles – form close social groups, will protect children or mates and play with each other.

The newest and largest section of the human brain is the Newest Brain – or Neocortex. The Neocortex is behind such qualities as reasoning, planning and speaking, and allows us, for example, to make decisions based on careful thinking rather than instinct.

As you’ll see in the following blinks, this three‑part brain schema helps us to understand why our behavior in relationships is often surprising.

Feelings of attachment are the product of neurotransmitters such as serotonin and oxytocin in the brain.

Emotions such as love or attachment feel so powerful and wonderful that we often think they must be the product of something as equally profound and mysterious.

Unfortunately, this isn’t true. Love and attachment are, like all feelings, the product of chemicals in the brain, called neurotransmitters.

There are three important neurotransmitters that influence our sense of attachment.

The first is serotonin and its role includes relieving feelings of anxiety and depression.

In some people, serotonin can even reduce the traumatic effects of grief and heartbreak when they lose a person with whom they felt a close attachment.

And for people in unhappy relationships, who can’t let go because they fear the feelings of loss, increasing their levels of serotonin – for example, by means of anti‑depressant meditations such as Prozac – can help them to finally make the break.

The second neurotransmitter responsible for attachment is oxytocin.

This chemical is present in high quantity during childbirth and is therefore responsible for the bond between mother and child. However, it also plays a role in the emotion of attachment throughout life too.

In a study of two species of prairie dog – the vole and the montane vole – Thomas Insel observed that, in adulthood, voles are monogamous: they mate for life and spend much of their day sitting side by side. In contrast, the montane vole, is a much less social creature: their display of attachment behavior is minimal, as they practice promiscuity and often abandon their young.

What could be behind such wildly different behavior?

Insel’s major insight was that the answer could be found in the brains of the two species – and the only difference he found between them was the level of oxytocin.

In the next blink, we’ll take a look at the third important chemical: opiates.