The Pith: In evolution if you want to win in the long run you don’t want all your eggs in one basket, even if that’s the choicest basket. Sh*t happens, and you better have some back up strategies.

Diversity is a major question in evolutionary biology. In particular, why is there so much diversity, so that the tree of life manifests a multitude of morphs? Might there not be some supreme replicator which emerges from the maelstrom to conquer all before it? This is actually the scenario which unfolds in much of science fiction, with monomorphic grey goo eating everything in its path (a more aesthetically differentiated variant of the super-species emerges in Brian W. Aldiss’  Helliconia Winter). As it is, life on earth does not seem to be converging upon an optimum phenotype for all individuals. In contrast, it seems to be going in the opposite direction broadly speaking (thinking on billion year scales), with the shift from the monotony of communal cyanobacteria to the riotous diversity of tropical forest biomes and coral reefs.

There are many ways you might be able to explain this diversity. Temporal and spatial heterogeneity produces perpetually shifting selection pressures, resulting in transient morphs one after the other. Negative frequency dependent selection, whereby the fitness of a phenotype runs up against its own success. This dynamic is one of the drivers of the Red Queen Hypothesis; the evolutionary arms race in some cases witnessing the resurrection of old techniques against which defenses are no longer recalled. Then there is the possibility that the lack of natural selection as an efficacious evolutionary force could allow for the diversification of phenotypes through  random drift. Finally, it may simply be that the gusher of mutation is powerful enough that novelty overwhelms selection and drift’s attempt to pare it back.

A new paper in Nature offers up another possibility. It does so by examining the fact that biological diversity remains operative even within a homogenized chemostat. A chemostat in this context refers to a controlled environment where inputs and outputs are balanced to maintain constant equilibrium conditions for a bacterialculture. Therefore, an unbeatable strategy should emerge in this medium perfectly tailored to the environmental constants, resulting in a homogeneous biota to match. Empirically this is not what occurs. So some explanation is warranted.

Metabolic trade-offs and the maintenance of the fittest and the flattest:

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My post earlier today prompted a few emails about the bizarre result that a substantial minority of Americans accept that the sun goes around the earth. The General Social Science variable is EARTHSUN, and it asks:

Now, does the Earth go around the Sun, or does the Sun go around the Earth?

The answers are “Earth around the Sun,” “Sun around the Earth,” and “Don’t Know.” A substantial minority of Americans answer #2. What’s going on here? This isn’t something limited to America. The same question has been asked internationally. I’ve underlined the geocentrism/heliocentrism question below:

I apologize for the small font. What you’re seeing though is that substantial minorities, on the order of 1/7th to 2/5th of people in the regions above give the wrong answer on whether the earth goes around the sun, or vice versa. Is geocentrism rampant? No, I don’t think so. My explanation is that many people don’t think scientifically habitually, so scientific facts aren’t background priors which pop up reflexively. On surveys which require a rapid first-blush reaction you may give the “intuitive” result, and only later realize that your answer was of course wrong. If you sat down and talked to most of the Americans who answered that the sun goes around the earth and showed them a solar system model and asked them about it I think they would be able to give the correct answer once properly primed in such a fashion.

Below is a side show generated from the GSS which measures reflexive geocentrism by demographic. I’ve combined the categories in the vocabulary test where N < 100 with their adjacent values. Remember that it is on a 0 to 10 scale, and correlates 0.70 with general intelligence. The educational category is broken down by the highest attained qualification.

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Whenever Zack Ajmal posts a new update to the Harappa Ancestry Project he appends some data to his ethnic database. This sends me to Wikipedia, because how many people are supposed to know what a “Muslim Rawther” means? Well, if you are a Muslim Rawther, and perhaps from Southern India, you would. But South Asian ethno-linguistic categories and hierarchies are notoriously Byzantine, and I have difficulty making sense of them. This isn’t too surprising in my case, as my family’s background is relatively mixed in the very recent past (e.g., Hindus and Muslims, and people of various caste backgrounds), so we’re not the sort who can go at length about our pure ancestry and all that stuff. Unfortunately, Wikipedia isn’t always useful, because the people editing the entries on particular South Asian ethnic groups are often people from those ethnic groups, so you get a lot of extraneous information, and a particular slant on how awesome and high achieving the group (also, sometimes there’s funny stuff about how notoriously good looking that particular caste!). On occasion there are other sources which are informative. For example, Zack has several individuals from the Tamil Nadar caste. I know a little about this group because 1) I have a friend whose family is Nadar (he’s American, so saying he’s an American Nadar is pretty worthless), 2) The New York Times profiled the group last fall.

When Zack noted that a group termed Tamil Vishwakarma had submitted entries, I went to Wikipedia. That was the first time I’d heard of the group. This is what I found:

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As I noted in my recent post on Malcolm Gladwell’s Outliers, Gladwell ignored the possibility that traits with a genetic component, other than IQ, might play a role in determining success. His approach reminded me of a useful paper by Samuel Bowles and Herbert Gintis from 2002 on the inheritance of inequality. Bowles and Gintis sought to explain the observed correlation between parental and child income (a correlation of around 0.4) by examining IQ, other genetic factors, environment, race and schooling.

As an example of the consequences of the transmission of income. Bowles and Gintis cited a paper by Hertz which showed that a son born to someone in the top decile of income had a 22.9 per cent chance of attaining that decile himself, compared to a 1.3 per cent chance for someone born to parents in the bottom decile. Conversely, a child born to parents in the top decile had only a 2.4 per cent chance of finishing in the lowest decile compared to over 31.2 per cent for those born to bottom decile parents.

As Gladwell did, Bowles and Gintis started their examination with IQ. To calculate the inheritance of income through genetically inherited IQ, Bowles and Gintis considered the correlation between parent IQ and income, the heritability of IQ from parent to child and the correlation between IQ and income for the child. Breaking this down, Bowles and Gintis used the following steps and estimates:

1. The correlation between parental income and IQ is 0.266.

2.If the parents’ genotypes are uncorrelated, the genetic correlation between the genotype of the parents and of the child is 0.5. This can be increased with assortive mating (people pairing with people more like themselves) to a maximum of one (clones mating). Bowles and Gintis use 0.6.

3.The heritability of IQ is 0.5.

4. The correlation between child income and IQ is 0.266.

Multiplying these four numbers together gives the intergenerational correlation of income due to genetically based transmission of IQ. I think there is a mistake in the calculations used by Bowles and Gintis, as they find an intergenerational correlation of 0.01, where I calculated 0.02. This leads to genetically inherited IQ variation explaining 5.3 per cent of the observed intergenerational correlation in income. Regardless of the error, this is a low proportion of the income heritability. (After I wrote this post I did a google search to find if someone had spotted this error before – and they had – on a earlier Gene Expression post on this same paper.)

I would have used some slightly higher numbers, but pushing the numbers to the edges of feasible estimates, such as increasing the correlation between income and IQ to 0.4, the genetically based correlation between parent and child IQ to 0.8 and the degree of assortive mating so that parent-child genotype correlation is 0.8 only yields an intergenerational correlation of 0.10. Genetically inherited IQ would account for approximately 26 per cent of the observed intergenerational correlation.

Unlike Gladwell, Bowles and Gintis then asked what role other genetic factors may play. By using twin studies, which provide an estimate of the degree of heritability of income (using the difference in correlation between fraternal and identical twins) and the degree of common environments of each type of twin, Bowles and Gintis estimated that genetic factors explain almost a third (0.12) of the 0.4 correlation between parent and child income. Loosening their assumptions on the degree of shared environments by identical twins compared to fraternal twins (i.e. assuming near identical environments for both identical and fraternal twins) can generate a higher estimate of the genetic basis of almost three-quarters of the variability in income.

From this, it seems that genetic inheritance plays an important role income transmission between generations. The obvious question is what these factors might be. I expect that patience or ability to delay gratification must play a role, although I would expect that there would be a broad suite of relevant personality traits. I would also expect that appearance and physical features would be relevant. Bowles and Gintis do not take their analysis to this point.

The authors finished their analysis with some consideration of other factors, and conclude that race, wealth and schooling are more important than IQ as a transmission mechanism of income across generations (although as the authors noted, they may have overestimated the importance of race by not including a measure of cognitive performance in the regression). That conclusion may be fair, but as they had already noted, there is a substantial unexplained genetic component.

This highlights the paper’s limitation, as once the specific idea that heritability of IQ is a substantial cause of intergenerational income inequality has been dented, the identification of other (but unknown) genetic factors leaves open a raft of questions about income heritability. Using Bowles and Gintis’s conservative estimates, we still have 25 per cent of income heritability being put down to genetic factors without any understanding of what these traits are and the extent of the role they play.

In their conclusion, Bowles and Gintis touch on whether policy interventions might be based on these results. They are somewhat vague in their recommendations, but suggest that rather than seeking zero intergenerational correlation, interventions should target correlations that are considered unfair. They suggest, as examples, that there are large majorities supporting compensation for inherited disabilities while intervention for good looks is not appropriate.

One thing I find interesting in an analysis of heritability such as this is that over a long enough time horizon, to the extent that someone with a trait has a fitness advantage (or disadvantage), the gene(s) behind the trait will move to fixation (or be eliminated) as long as heritability is not zero. The degree of heritability is relevant only to the rate at which this occurs and only in a short-term context. The obvious question then becomes (which is besides the point of this post) whether IQ currently yields a fitness advantage. Over a long enough time period, variation will tend to eliminate itself and Bowles and Gintis would be unable to find any evidence of IQ heritability affecting income across generations.

**This a cross-post from my blog Evolving Economics, which is my usual blogging home.

Bowles, S., & Gintis, H. (2002). The Inheritance of Inequality Journal of Economic Perspectives, 16 (3), 3-30 DOI: 10.1257/089533002760278686

The Audacious Epigone has a post up, Republicans are more scientifically literate than Democrats or independents are, where he reviews pro vs. anti-science attitude by party in the General Social Survey. He concludes that in fact Republicans are more scientifically literate across the issues than Democrats. Jason Malloy saw this trend four years ago in the GSS, and to some extent so have I. One point to keep in mind is that a few specific politicized scientific issues are very much the outliers in exhibiting tight partisan valences in opinion.

So another question: are conservatives more scientifically literate than liberals? If scientific literacy correlates with being Republican, and being Republican correlates with being conservative, shouldn’t scientific literacy correlate with being conservative? Not necessarily. Such correlations are not transitive. Generally what I’ve seen in the survey data is that Republicans tend to be more pro-science than conservatives. I think part of it is the voting by economic position which has become less stark in our culture, but still remains a force. In any case, my table to accompany AE’s is below. I used his variables:

ASTROSCI, SCIBNFTS, EXPDESGN, ODDS1, HOTCORE, RADIOACT, BOYORGRL, LASERS, ELECTRON, VIRUSES, CONDRIFT, EVOLVED, EARTHSUN, SOLARREV, EATGM, ICESHEET, SCITEST5, GRNTEST1, GRNTEST5.

For political ideology, it’s pretty simple: POLVIEWS(r: 1-3 “Liberal” ; 4 “Moderate”; 5-7 “Conservative”)

The percentages given are the correct science answer, or the more pro-science answer. If you want to know my criteria for that, don’t ask, just go to the General Social Survey website and enter in the variables above, and you’ll see the results and understand clearly how I categorized things.

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I’m going to promote a comment:

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In 2006-2007 I worked at a firm which had its own web application, and “web 2.0” was a big term in the marketing materials. This article in DealB%k, Is It a New Tech Bubble? Let’s See if It Pops, made me wonder what happened to that term.

Here’s Google Trends:

Since it doesn’t show up in my total content aggregator (RSS), and I don’t know how to author filter Movable Type posts easily, I thought I would point to my guest posts over at the Sepia Mutiny weblog:

Speaking of a demonstration in Pakistan….

The decline of Hindi among American brown folk

A civilization of regions

Do that Guju you do!

The undersampled 1 billion (genetically that is)

If you don’t know about the blog, here’s the Wikipedia entry. I’ve been commenting on that site since its inception in the summer of 2004, as two friends were co-founders.

Addendum: I push all the stuff in my total content aggregator to my twitter account, Gene Expression Facebook page (though this includes GNXP.com posts not by me), and my Facebook page. I’ve also got a NetworkedBlogs page which you can subscribe to or something. Probably other things I’ve forgotten about to be honest (e.g., here’s my Talk Islam author page. Don’t contribute there anymore).  Also, I should mention that Razib on Books has its own domain, razibkhanbooks.com. Everything posted there is pushed into the total content aggregator, and the “posts” will usually be pointers to this weblog anyhow, but here’s the specific feed if you care (someone inquired, so someone cares!).

Reader “Diogenes,” with ADMIXTURE in hand, and way more knowledge of archaeology than I can comprehend, now has a blog. Why am I starting a blog…:

I named my blog Artemis since I believe the “Neolithic” which shaped our world for the last 10,000 years is now ending. Demeter’s shackles are broken.

I’m starting my own Project playing with ADMIXTURE and other programs. I’m not a scientist (even though I work in a field related to biology), but I’ll try to substantiate my thoughts whenever possible.

His interest seems to be the Neolithic Revolution/Evolution in Europe.

1) First, a post from the past: 10 questions for Jim Crow. Arguably the doyen of modern population geneticists. Take a look at who he’s had as graduate students or post-docs, and there’s a high probability there is someone you know of, you’ve met, or you know of by reputation (at least if you have some association with pop gen).

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