How humans emerged in their present form

This page does not fit in with the thinking of some religious movements and you may prefer to pass it over if you are a Creationist.

Otherwise, over 60 million years ago, the dinosaurs ruled the globe.

Mammals, from whence humans came, kept a low profile at that time and they were of small build. They were able to survive underground, through many nuclear winters, after the dinosaurs became extinct. As far as is known, the Earth received a direct hit from a large asteroid and this created a mass extinction event. It had global impact on life and rock formations (and is known to geologists as the” K/T event”).

At even earlier times, 100’s of millions years before, mammals did not exist and reptiles ruled the roost – in the seas and, later, on the land. Mammals still possess an ‘inheritance’ from our reptilian ancestors – namely, our brain stem and our cerebellum. This reptilian brain, in the darker shade, below, still keeps us functioning without conscious thought; our breathing and heart and sleep patterns are monitored and regulated 24/7.

In other parts of the website, I have referred to the reptilian brain and the early mammalian brain as the ‘older, and not so smart sibling’. These are labelled in a diagram, below,  that helps to identify the ‘reptilian’ brain, from the early mammalian brain, and our modern human brain (labelled by me as the’ ‘smarter and younger sibling’).

source: Kaja Nordengen Your Superstar Brain

That early mammalian brain, and its reptilian base, evolved over tens of millions of years until, around:

4 million years ago: early hominids, now a class of mammal, started to walk on two legs. These hominids possessed a brain weighing less than a kilo.

2 million years ago: homo habilis began working with tools.

1 million years ago: homo erectus saw the brain gaining weight to about 1 kilo; with enough capability to manage fire and develop hunting techniques.

Less than 1/2 million years ago: homo sapiens, modern man emerged with further development of the brain, then weighing almost 1.5 kilos There is evidence of ‘thinking’ and creativity.

Only a little over 100 thousand years ago, homo sapiens, the modern human, began to provide concrete evidence of abstract or symbolic thought culminating in evidence of jewellery-making appearing less than some 50 thousand years ago.

As far as we can tell, that ability evolved to permit the complex erection of structures such as the Pyramids less than 5 thousand years ago. There is argument about these dates as there is some suggestion that other ‘mass extinction’ events swept aside earlier evidence of creative communities of humans.

… but size did not matter! Other mammals, dolphins and cows, have a brain of similar size to humans but the human brain shows an ability to innovate. For instance, the brain of the Blue Whale is around 8 kilos, considerably bigger than our own (but it does have to manage a body weighing some 170 tons!)

When it comes to creativity and innovation, what seems to make the difference are the number and size of the neurons in the brain. I am told there are some 86 billion neurons in a modern human brain, with 16 billion located in the cerebral cortex (the ‘smarter and younger sibling’). It is in the number and location of our neurons that human beings stand out from other animals.

It would appear that we owe our success, as a species, to our ability to handle difficult situations and to make friends (that is, to keep our friends close, and our enemies even closer). Stephen Porges is clear that this ‘social engagement system’, as he called it, emerged from changes to the Vagal system, an ancient control mechanism. He labelled that social engagement system the Ventral Vagus as it worked in and around the upper part of our body.

By contrast. the more ‘primitive’ Dorsal Vagus, operating in the lower body, and behaving more like the ‘reptiles’, can help us in a time of crisis. Tomanage those times of severe threat, we depend on strategies that a reptile could use efficiently e.g. slow rates of breathing. Sadly, mammals, particualrly humans suffer side effects that are problematic and contribute, at least in part, to our tricky responses ot trauma.

Elsewhere, I have discussed the detailed workings of different brain parts,  For the present, suffice it to say that one key area that has much impact on our modern behaviour is the amygdala. This limbic nucleus,  and the Vagus nerve,  play a key role in deciding whether – in an instant – we will fight, fly, freeze or faint in order to stay alive in the face of threat. It is the impact of these aspects of a nervous system that play a large part in our survival and in sustaining emotional and bodily regulation in the face of threat. Called on too frequently, and the amygdala starts to play up.

Much of this website is devoted to small, safe experiments intended to make us more aware of the behaviour generated by this ‘not so smart and older sibling’. If I had one intention in constructing this website, it would be:

  • to help others become more aware of the changes they can make to help themselves in a time of crisis, and
  • to discriminate those things that are beyond our immediate control, and
  • to practice the art of responding to the difference between the two.

Return to:


What is a Nudge

Fight, Fight and Freeze