Bloodthirsty Brains: Study Challenges Evolutionary Development of the Human Brain

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http://neurosciencenews.com/brain-evolution-development-4940/

The size of the average human brain has increased in size by about 350% over the course of human evolution.  Previously it was thought that this increase in size was the reason for the advancement of human intelligence.  However, new research has found that this may not be the only reason for this increase in intelligence.  While brain size has increased significantly, so has blood flow to the brain.  Research has found that blood flow to the brain has increased by 600%, and that this increases seems to correspond with the evolution of human intelligence. 

Previously studying the evolution of human cognition was limited to estimating brain size from discovered human skulls.  However, scientists say that cognition could be more accurately understood through the measure of cerebral metabolic rate.  Metabolic rate in the brain is proportional to cerebral blood flow rate, and for this reason scientists have turned to measuring the holes in the skull that the arteries supplying blood to the brain (the internal carotid arteries) would have passed through.  What they have found is that the size of the holes has increased over the past 3 million years.  The scientists were able to use these measurements to calculate the cerebral perfusion rate.

The results of this study indicate that the rate of perfusion in 11 species of hominin ancestors not only increases, but increases at a faster rate than brain size.  What this means is that the metabolic rate of human brains was increasing faster than brains size, and therefore was a greater contributor to the increase in intelligence.  This is because an increase in the blood supplies to the brain would allow for increased interneuron connectivity, synaptic activity, and cognitive function. 

I thought that this discovery was very interesting because it offers a more complete understanding of how human cognition and intelligence was able to evolve.  An increase in brain size did not seem like it could be the whole story, especially after learning in class that having a larger brain does not necessarily mean that you are more intelligent.  This article also made me think about the possible directions that the evolution of the human brain can take from here; it makes me wonder if in the future humans will have even more increase the blood flow to the brain.  This article also makes me wonder if there is another factor which could have contributed to this evolution since now we know it was not just an increase in brain size.

Comments

  1. Jared McGinleyDecember 7, 2016 at 11:54 AM

    No one commented on this!? That's a shame. Rachel, this is a really good article choice and provides some much-needed insight into understanding why humans have evolved to be so much more intelligent than other species. I appreciate this article choice and plan to look further into this topic so that I can see whether I should teach about it in future semesters.

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