Reification is alright by me!

By Razib Khan | May 8, 2012 1:01 am

Long time readers know that I’m generally OK with reification as long as we don’t take it too seriously. And we do that all the time. An “object” is really only an “object” in a human-sense. Reduced down to particle physics it is an altogether different entity. But on the human-scale asserting that a chair is indeed a chair, rather than cellulose, etc., (or now, polymers), and further down basic macromolecules, is a useful “fudge.” Similarly, I’m generally skeptical of the idea that we have a clear & distinct model for what a “species” is. The framework is very different when you’re talking about prokaryotes, as opposed to plants, as opposed to mammals. The question is not species, but what utility or instrumental value does the category or class species have?

For most of the stuff I’m concerned with, the messy shapes of reality which are the purview of biological science, we are all fundamentally nominalists in our metaphysic. We may accept that we’re idealists in the sense of cognitive or evolutionary psychology, but human intuition does not make it so. The categories and classes we construct are simply the semantic sugar which makes the reality go down easier. They should never get confused for the reality that is, the reality which we perceive but darkly and with biased lenses. The hyper-relativists and subjectivists who are moderately fashionable in some humane studies today are correct to point out that science is a human construction and endeavor. Where they go wrong is that they are often ignorant of the fact that the orderliness of many facets of nature is such that even human ignorance and stupidity can be overcome with adherence to particular methods and institutional checks and balances. The predictive power of modern science, giving rise to modern engineering, is the proof of its validity. No talk or argumentation is needed. Boot up your computer. Drive your car.

All this is to preface my explanation of my post below, “Finding Fake Roots.” Some readers & commenters were a bit confused or unclear at what I was getting at. Here in a nutshell is the problem as I see it: in Finding Your Roots Henry Louis Gates Jr. shifts back and forth between uniparental phylogenies, more contemporary model clustering assessments of genetic relatedness and relationships, and natural history. The map above illustrates human migrations as they were commonly depicted in the mid-2000s during the peak of uniparental lineages. By uniparental, I mean the direct maternal line, as defined by mtDNA, and the direct paternal line, as defined by Y chromosomes. These two methods were easy to conceive as a phylogentic tree, because that’s what these two genomic regions are. There’s no recombination; mixing & matching between parents. You get your Y from your paternal lineage (if you are male), and your mtDNA from your mother. These neat phylogenetic trees of mtDNA and Y chromosomal lineages were then easily transposed to a spatial and temporal scale. Ergo, nice cartographic infographics like the one above.

But all good things come to an end. With “SNP chips,” which allow researchers to type individuals across hundreds of thousands of markers, we now are at the stage where we can move beyond the direct maternal and paternal lines. Rather than just one line of descent, we get a full picture of one’s ancestors. To the left are my daughter’s result from 23andMe. As I have noted before, I’m 99% sure there’s a problem with their results for people with particular mixed ancestries (my half East Asian/European friends get good results, so I assume it’s a reference population problem). She is about 40 percent South Asian on ADMIXTURE, and that makes sense since I’m 80-90 percent South Asian (the balance is East Asian, which is not surprising due to my family’s origin). But let’s put that to the side. What are these results telling us? These algorithms are powerful. But we always need to be very careful about imposing our own frame upon them. They are excellent at gauging genetic relatedness, but they are not so excellent at telling us our history.

To the left is my best guess at “my history.” I’m 80-90% South Asian. That’s pretty clear, and will show up on any clustering algorithm with explicit models. It will also be clear on a PCA, where South Asians can shake out as their own independent dimension. But 10,000 years ago South Asians as we understand them genetically probably did not exist. By probably, I’m about 95% sure. The genetic analyses which support this proposition are abstruse, but they make sense of a great deal of other data. The South Asian genetic cluster is a real one, but it is compound formed within the last 10,000 years of two very distinct populations. Just because it is a hybrid does not mean that one should automatically reduce it to its antecedents. Many “real” populations originate as hybrids. Similarly, I think that there is a high chance that Europeans, as we understand them today, did not exist 10,000 years ago. Rather, modern Europeans as well may be a compound of various populations which expanded demographically, and synthesized with each other, between the end of the Ice Age and history.

In my post below some commenters argued that obviously implausible inferences from a thin set of reference populations are acceptable considering Henry Louis Gates Jr’s target audience. But that really wasn’t my main point. Rather, it was that he was eliding the distinction between uniparental markers, and the clusters generated by modeled based ancestry assignment algorithms, and ascribing the phylogenies of the former to the latter. It is important to note that categories like “Europeans” are only approximations. But they’re damn good approximations today! Nevertheless, note the qualification of time: they may have basically no meaning at some point in the recent past. They’re powerful when it comes to precisely partitioning modern variation, but they don’t tell us the history of that variation.

When constructs lead us to a false perception of reality, we’re using them incorrectly. We shouldn’t blame the abstractions. Rather, we should blame humans. Ourselves.

CATEGORIZED UNDER: Anthroplogy
  • Nihaya Khateb

    I suppose that these DNA scales are just an indicator for our basic genetic structure. But in this model they could not tell us nothing about our emmergent feateurs that come out as a result of recombination and cross-over. Take for example someone genetic scale: He is 60% european and 40% South-Asian, still this could not tell anything about his real features, is his brain european? or Asian? onley apparent physical features could be obvious, but mental features that are the most important characters are not indicated in this scales. So, theoritically we could reduce humans to their genome components but it could tell noyhing about his real mental and cognitive features.
    Because of the human out-bred over the history, it’s obvious that it is very difficult to find pure genetic “races”. However, populations that insest to in-bred and isolate themselves for many generations from the other populations they are relatively pure “races” and is very easy to tell their features even the mental ones from their DNA scales.

  • Kaviani

    People should be required to read this before any other posts on race or social constructs we take for granted with regard to identity or biology. Excellent.

  • http://www.textonthebeach.com Seth

    Informative post. The last few sentences are more or less what I try to get across to the hyper-relativists, the people who have misread Kuhn too many times. However, I don’t think there are many of them left in the humanities and social sciences today. Rather, what you have are calls for “ethical constructs,” which is to say, models and abstractions that only support or fit in with a particular politically correct vision of society.

    Hence, Gates’s show is all about deconstructing race, not about exploring the nuances of scientific models. See also the reaction to this study of black students GPAs. Most critiques weren’t about the design or methods of the study; the critics said that, whether or not the study captured something empirical, it should not have been published because it inflates racial tension.

  • ryan

    I might think the 10k bp map should also have little chicken pox in a lot of different places and somewhat less dense hives in the Middle East and South Asia

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    #4, agreed. i think i got 85 percent though.

  • Sandra

    I am glad to see the honesty on this site,regarding the DNA/the Gates programming.I was beginning to understand DNA more fully,when I decided to contact Ancestry.com and Family Tree.Mistake on my part! I am now confused about my MtDna results. I had tested with both companies and via telephone,told that I am “rare”. This cannot be true since I am Haplogroup H. H is not rare and with this statement,I was told by both companies that since I am 72g,263g,it’s the 72g that makes me “rare”.When I pressed them for an explanation,one could not be given by either Ancestry.com or Family Tree. I am now wondering if this DNA testing is a fraud just to get people’s money or that the “experts” really are not what they claim.I do wish that someone could give me an answer,but I suppose that will not happen. This site is very interesting.Thank you.

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

ADVERTISEMENT

See More

ADVERTISEMENT

RSS Razib’s Pinboard

Edifying books

Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »