Human brain and evolution

In my recent discussions with some of my friends I have repeatedly come upon this insight that the human brains have remained unchanged for over 30,000 years (at least) i.e. the hunter gatherer humans, Harappan peoples, Huns, Romans etc. have had the same brains with the same cognitive abilities as we did. I find this idea to be amazing because it has a lot of implications on how we currently view and understand things. I came across this idea first from this Kurzgesagt video talking about human origins. They say that we could go back approximately 50,000 years ago, kidnap a human baby and raise it without noticing any difference in today's world. But, some research into this makes this more interesting.

Evolution of anatomically modern humans ASH have been estimated to be over 300,000 years ago, with latest estimates of humans showing gracile features from around 50,000-30,000 years ago. This report by the Max Planck Institute of Evolutionary Anthropology pushes back the origin of modern humans by 100,000 years to over 300,000 years ago, i.e. fossils with the same facial characteristics as modern humans have been documented from this time. While the body of the modern humans have been identified, researchers citing a newer finding say that the modern human brain continued to evolve along with the Homo Sapiens lineage and that only fossils less than 35,000 years ago show the same cranial shape as that of humans today.

Information about humans from very long ago is typically confirmed using various paleo-archaeological methods, the most common among them being:
— measurements obtained from hominid findings
— genetic analysis of both remains and present day humans
— evolutionary observations from other animals

These are typically combined with anthropology, linguistics, geography and environmental studies to form a more complete picture.

Further, it is known that humans are still evolving. Genetic mutations in humans continue to occur, some of which lead to long term changes in the species. One such mutation related to brain size has been identified in certain populations from around 5,800 years ago. These indicate that human brain size (cranial volume) has actually reduced. This nice article describes how our brains are changing in different ways. While humans today have slightly smaller brains, it is difficult to ascertain if there have been any changes in intelligence itself. There have been attempts to explain this reduction in brain size with various theories. Some of them as described in the above article are:

1. Global warming and the reduction in the polar ice caps lead to a warmer planet and thus pushed all animal life to reduce body size that also lead to a reduction in the brain size.
2. Increasing social complexity lead to task specialisation that in turn reduced the need for individual humans to expend energy in trying to maintain a bigger brain.
3. It has been observed that domestication leads to a smaller brain. Domesticated dogs have a smaller brain than their wolf ancestors but show intelligence on different levels. The idea is that human could have domesticated themselves leading to a smaller brain in the process. One of the aspects of this is also reduced aggression, with humans today supposedly being far less aggressive than humans 10,000 years ago. Reduced aggression coupled with co-operation and communication lead us to what we are today.

Irrespective of what caused the reduction in brain size, we can therefore gain the following main insights:

1. Modern day humans with a similar and stable genetic and anatomical structures can be found up to 30,000 years ago.
2. There have been very small changes in human brain size from around 5800 years ago. Humans 10,000 years ago had slightly bigger brains that we do today, but it is difficult to ascertain if there have been any changes in intelligence and that is because intelligence itself is difficult to define.
3. Stable genetic mutations have been observed in certain populations of humans over the past 5,000-10,000 years. These mutations such as those involving blue eyes, lactose intolerance, sickle cell anaemia etc. have been observed but we do not know yet if they are stable evolutionary changes because of the long time frame necessary for evolutionary changes to occur.
4. It is safe to assume that, on average, humans up to 5,000 years ago (after reduction in brain size) had similar brains as we do today. That time is the beginning of civilisations, organised religion and kingdoms, approximately 5,000 years after humans started farming and built cities.

Now I think that implication of these insights are what is most interesting^. They are:

1. People back then (5,000 years ago) had the same brains, and hence the same thoughts, feelings, cognitive abilities and emotions as we did. They possibly interacted with each other in very similar ways. The only things that have changed are the availability of a range of information and technologies.
2. Valid principles, concepts and methods established back throughout human history, when based on observations of human brain and behaviour might then still hold true. This would include social systems, religions, administrative policies and psychological tactics.
3. Empirical knowledge based on the hitherto unchanged human brain and behaviour would still be valid.

I found this realisation quite humbling. To think, that the main thoughts of a Roman soldier standing guard in a remote German outpost would have been those of food and a warm bath or that the ancient Harappan peoples approached difficult problems with the same cognitive tools as we have today. This could also mean that observations made by thinkers such as the Buddha on the human behaviour and how to cope with them would scientifically still be applicable today. What could this mean for modern psychology?

^ Here I make a relatively harmless assumption (I think) that brain and behaviour are closely linked, and that similar brains lead to similar behaviours. While this is true in general, it is important to say that we do not know in detail all the variables that are involved. Could the behaviour of humans a few thousand years ago be completely different from that of today due to some external environmental factors that we do know of?

tags: #culture #history