Building The Genetic Bridge

Now that scientists have decoded the genome for humans and all great apes, we can now start to identify all of the functional genes that make us different.  One such gene was discovered recently: MIR941-1 (Hu et al. 2012).  This gene encodes human specific microRNA that is not present in our closest relatives, or any other known mammals.  And it may be the start to building a complete understanding of what functionally separates our genetic structure from the rest of the animal kingdom.

What Does It Do?

MIR941-1 regulates cellular differentiation and neurotransmitter signaling.  Specifically, it plays a role in human-specific cognitive functions like language and speech, and it also affects pathways that increase the human lifespan.  What is most interesting is that when there is a problem with the brain region producing miR-941 microRNA, people display “mental retardation, developmental delay, as well as speech and language defects.” (Hu et al., 2012).

Exercise Caution

To clarify, this is not the gene responsible for human intelligence.  In all likelihood there is not one-single gene that gives us the cognitive capacity we enjoy over other animals.  Uncovering the complex genetic relationships and pathways that make us human will be a very long process, and will likely include the discovery of other genes similar to MIR941-1.  But it is still an important discovery because it shows us that scientists now have the data and technology to start “building the genetic bridge” that separates humans from great apes.

All too often, the popular scientific media exaggerates the importance of interesting genetic discoveries, because they want to break a simplistic story of the one gene that makes us special.  FOXP2 was a gene that was described in this way back in 2003.  Jerry Coyne gives a fantastic explanation of how this was done with the discovery of miR-941 on his blog Why Evolution Is True.  A basic rule of thumb would be to never believe any post that claimed there was a very basic Mendelian inheritance pattern between a few genes and our uniqueness.  As evolutionary scientists have discovered over the past few decades, genes that are related to cognitive functioning very rarely display this type of pattern.  More research should reveal other genes that play an important role in our uniqueness from the great apes, but is exciting to know that we have identified one key gene and region of the brain that seems to play a very important role.

When Did It Appear?

Future research on this specific gene should also help us understand more about our evolution as a species.  At the moment, we know that the gene appeared very rapidly between 6-1 million years ago.  This is critical because it is the period of human evolution when our ancestors evolved from early stem hominins to ancestral Homo.  Unfortunately, it does not tell us anything about when this critical gene became fixed, and consequently, what species first acquired it.  Understanding this development in more detail may help us to understand a great deal more about the evolution of human language.  Theories in the 1980s and 1990s posited that human language emerged during the Upper Paleolithic, a mere 40,000 years ago (Diamond, 1994; Klein, 1995).  However, more recent anatomical (Nishimura, 2002), cultural (Bar-Yosef, 2002), primatological (Dunbar, 2001), and genetic data (Enard et al., 2002) has revealed that the first modern humans that emerged 200,000 years ago, likely had what we would call modern human language.  The discovery of MIR941-1 could push that date back even further.  If a gene that plays a unique and specific role in enabling human language and speech existed as early as 1 million years ago, it is likely many ancient hominids had more complex language abilities than do contemporary great apes.

Concluding Thoughts…

This discovery is extremely interesting.  It could represent the start of our attempt to understand all of the genes that are functional and unique to our species.  However, genetics is very complicated, and it should not be viewed as the gene that separates us from the great apes.  Future research will need to be conducted to both better understand the significance of the role MIR941-1 has in modern day human populations and our ancestors.  Future research will also be needed to better understand what other genes play a role in our cognitive abilities.  It is an exciting time to study human origins – as I’m sure it always has – and hopefully always will.

References:

Bar-Yosef, O.  2002.  The Upper Paleolithic Revolution.  Annual Review of Anthropology, 31, 363-393.

Diamond, J. (Ed. Campbell, and William Schopf, J.)  1994.  The Evolution of Human Creativity.  InCreative Evolution?! (pp. 75-82).  Los Angeles: Jonas and Barlett Publishers.

Dunbar, R.  2001.  Brains on Two Legs: Group Size and the Evolution of Intelligence.  In Tree of Origin: What Primate Behavior Can Tell Us about Human Social Evolution (173-191).  London: Harvard University Press.

Enard, Przeworski, Fisher, Lai, Wiebe, Kitano, Monaco, and Paabo, S. 2002.  Molecular evolution of FOXP2, a gene involved in speech and language.  Nature, 418, 869-872.

Klein, R.  1995.  Anatomy, Behavior, and Modern Human Origins.   Journal of World Prehistory, 9(2), 167-198.

Hu, H.Y., et al. 2012.  Evolution of the human0-specific microRNA miR941.  Nautre Communications 3, Article number: 1145 doi: 10.1038/ncomms2146

Nishimura, T.  2002.  Comparative morphology of the hyo-laryngeal complex in two steps in the evolution of the descent of the larynx.  Primates, 44, 41-49.

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About Cadell Last
Hello. I'm probably drinking coffee and reading.

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