Sunday, September 28, 2014

Neanderthals - Real Human Differences and Stereotypes

That's right - I am 2.1% Neanderthal.  There have been some fascinating developments in human paleogenetics in the past decade including the characterization of genomes other hominins including the Neanderthals and the Denisovans from old remains.  It casts a different light on some of the stories based on stereotypes from the past.  For example, the common view of Neanderthals were that they were strong, but not very intelligent or sophisticated beings.  As as result Homo sapiens could easily outcompete these brutes and as a result modern day man is the only surviving species.  It was quite a surprise to learn that after the Neanderthal genome had been characterized portions of it could be identified in the modern human genome and that ancient DNA may have a role in the HLA (human leukocyte antigen) genes that play a central role in immunity.  There is the related question about whether incorporating the DNA of a new species could lead to certain autoimmune problems.   That fact compounded my interest in this area that was originally piqued by the first NatGeo Genographics project.  That project gave confirmation and graphics to the fact that at some point or another about 60-70,000 years ago, our ancestors walked out of the Rift Valley in East Africa and began their migrations around the globe.  Some of those folks migrating north through Europe encountered Neanderthals and Denisovans along the way.  Contrary to the conventional story that humans "outcompeted" them, they mated and produced offspring.

A quick review on relevant taxonomy.  From zoology, the naming convention is Genus and species.  Modern humans are Homo sapiens.  Considering this convention there were about 16 different species of the genus Homo and apart from Homo sapiens all of the others are extinct.   That includes Neanderthals (Homo neanderthalensis) and Denisovans.  In historical terms, at one time or another there was more than one Homo genus walking the earth.  Looking at a graphic from the Smithsonian suggests that Homo sapiens, Homo floresiensis,  Neanderthals (Homo neanderthalensis), and Denisovans were all walking the Earth sometime in the time zone about 20-30,000 years ago.  Genetic technology has revolutionized this area of morphology based research.  There is a lot of speculation but no good conclusions about why Homo sapiens is the only surviving species.

I don't know if they still teach this in Medical School but in all of my major rotations I was taught to describe the patient in the first sentence by age, sex, and ethnicity based on outward appearance.  There were various rationales provided for that opening sentence but even in medical school (now a long time ago) they did not make a lot of sense to me.  Of course there were cultural and political influences on these descriptions.   The "38 year old black male..." became the "38 year old African-American male..." at some point and back again depending on the politically correct term of the time.  It was all very unscientific, but many physicians seemed to think that it was a more medically precise way to talk about the patient and condense relevant information about that patient.  I did not have to consider anything beyond "male-female" versus "man-woman" to decide that my notes would never start with these words.  The only facts that I capture in my opening lines is the actual age of the patient and whether they are a man or a woman.  Male and female are non-specific terms and don't reflect the fact that I am talking about a human being.  You could say that this is an old convention, but I still see it as present in most medical records that I review.  In fact, it has stretched so that in some cases the characterization of white people has progressed from White to Caucasian to European, even though the person in question and their family has not set foot in Europe in over three or four generations.  I guess I also missed the politically correct convention that white folks were now "European Americans" and yet I have seen that frequently in medical records.

I read a paper in Science about 20 years ago that there were no genetically significant differences based on race or skin color.  It what seemed like a surprisingly simple statement, the authors pointed out that all humans are much more genetically related to one another than to non-human primates.  Genetic differences based on skin color and facial features were trivial to non-existent.  If you look at it that way that opening line:  "24 year old Hispanic female..." becomes little more than an unscientific stereotype.  Why include it in the medical record?  Some might say that it provides the opportunity for the delivery of culturally appropriate health care.  If that is the case, I would suggest including a more accurate description of the patients culture (as described by them) rather than presuming their culture based on their physical appearance or a check off on a standard intake form.  Scientific rather than stereotyped descriptions of people should be the standard.

A related issue is how much people actually know about themselves and their family of origin.  On the average, most of the people I talk with about their family histories know the high points for about 3 generations.  Physicians are typically focused on heritable diseases but most third and fourth generation Americans in this country don't know much about how their families migrated to the US and where they were migrating before that.  The first humans migrated out of the Rift Valley in East Africa about 70,000 years ago.  That is 2800 generations ago, maybe more if we need to correct for the short longevity of prehistoric man.  The fact that we are all Africans to start with and that so-called racial differences were a byproduct of the migration is a huge fact that nobody talks about.  It has far reaching implications and it is why I like to talk about it.

The other issue is what happened to the Neanderthals?  The story used to be that the Neanderthals were typical cave men.  They were squat muscular, and not very bright.  Their fate was considered to be extinction because they were outclassed and outcompeted by Homo sapiens.  Paleogenetics has led to those assumptions being challenged.  An excellent Nova special called Decoding Neanderthals captures some of the surprise and excitement of some of the first scientists who discovered Neanderthal DNA in the human genome.  That program also looks at how inferences can be made about prehistoric beings based on both the archaeological evidence and the genetic evidence.  In the case of archeology, the complexity of Neanderthal flint tool technology was investigated.  They had a method of making flint tools with a broad sharp edge that could be resharpened.  It was termed Levallois technology and the complexity suggests a higher level of intelligence than is commonly assumed.  The second Neanderthal technology that was discovered was using a type of pitch on some of their implements.  To manufacture this early epoxy required mastery of a thermal process again suggesting advanced intelligence.  The final piece of evidence is the presence of the FOXP2 gene.  This gene is responsible for speech and language in humans.  There are FOXP2 variants, but when the Neanderthal DNA was decoded, it contained a copy of the FOXP2 gene identical to modern humans.  That technology and the fact that Neanderthals were also social beings makes it a little more difficult to explain how they were "outcompeted" by Homo sapiens.  I have not seen any theories about how that competition might have included direct incorporation of large numbers of Neanderthals directly into the Homo sapiens population.  What are the numbers of Neanderthals who could have been incorporated into the population given the current DNA percentages?  I suspect that it could have been large.   

 To use an example from my own ancestors, I constructed a table looking at the stated ethnicities of my grandparents.  My maternal grandparents had been in the US for a generation longer.  My paternal grandmother still spoke and read her native language.  My maternal grandfather knew just small bits of Swedish.  He taught me a prayer in Swedish but did not know the translation and neither do I.  Small customs usually having to do with celebrations and food persisted to a small degree but on the balance my family was Americanized.  Comparing the stated ethnicities of my grandparents to DNA markers results in a couple of matches, but as many question marks.

Will there come a time when genetics will allow for better probability statements about who might inherit what disease?  Given the fact that my haplotypes occur in less than 1% of the current NatGeo database of over 650,000 subject - maybe.  But that depends on a lot more study and a medical record descriptor about presumed ethnicity has very little to do with it.  There is a related issue about how the science of paleogenetics can be politicized like any other branch of science.  Chris Stringer wrote an excellent commentary about this in Nature.  He observed a trend speculating that some genomes were more "modern" than others based on their content of "ancient" DNA.  He summarizes this well in two sentences:

"Some of us have more DNA from archaic populations than others, but the great majority of our genes, morphology and behavior derives from our common African heritage.  And what unites us should take precedence over that which distinguishes us from each other."

The current evidence also seems to suggest that the migration out of Africa is only part of the story.  The identical FOXP2 gene found in both Neanderthals and modern humans, suggests a common ancestor long before the African migration.  There are currently 7 billion people on earth.  The processing power of the human brain means that there are 7 billion unique conscious states.  It should not be too difficult to imagine that isolated groups of humans in in recent times will result in different  appearances, customs and practices.  The all too human characteristic of promoting the interests of these groups even to the point of warfare against others seems to be a common element of human consciousness.

A more widespread appreciation that these distinctions are by convention only might moderate a tendency for groups to see themselves as different or "better" than other groups of modern humans.  That leap of consciousness will hopefully happen in future generations.

George Dawson, MD, DFAPA

Supplementary 1:  One of the most striking aspects of this project is the economics of it all.  Over 680,000 people willing to pay $200 apiece for this information.  Researchers take note.  This may be a new way to fund research and generate large amounts of data at the same time.  You probably need a willing department head,  IT department, and IRB.  There is also a question of collaboration.  Is there any correlate between mental illnesses and the genomes of the Neanderthals and Denisovans?  If I have a well characterized sample of research subjects with a specific problem does it make sense to look at that issue?

Supplementary 2:  There are currently only 19 references to the issues of ancient DNA in Medline at this time.  Seems like another good area for research.

Supplementary 3:   My old high school biology text was ahead of its time in another way.  I remember that it predicted that the human race would eventually appear to be uniform due to increased mobility and intermixing of different races.

Supplementary 4:  The infographic at the top of this post was generated by the National Geographic Genographic Project based on my DNA sample.

Supplementary 5:  The evidence of bias against Neanderthals in popular culture is significant.  My first thought was the Geico commercials based on the premise: " three pre-historic men who must battle prejudice as they attempt to live as normal thirty somethings in modern Atlanta".  Even the Wiki piece refers to them as "Neanderthal-like".  Wikipedia has interesting references on this page and also a separate page entitled "Neanderthals in popular culture."

Supplementary 6:  Updated NatGeo infographic accessed on April 9, 2016.  NatGeo knows how to make a world class infographic.  Note that the sample size has gone from 678,632 to 742,652.  The remaining details are about the same but there is more updated information on the web site.


1:  Stringer C.   Evolution: What makes a modern human.  Nature. 2012  May 2;485(7396):33-5. doi: 10.1038/485033a. PubMed PMID: 22552077.

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