Below I note that sex matters when it comes to evolution, specifically in the case of how sexual reproduction forces the bits of the genome to be passed back and forth across sexes. In fact, the origin of sex is arguably the most important evolutionary question after the origin of species, and it remains one of the most active areas of research in evolutionary genetics. More specifically the existence of males, who do not bear offspring themselves but seem to be transient gene carriers is a major conundrum. But that’s not the main issue in this post. Let’s take the existence of males as a given. How do sex differences play out in evolutionary terms shaping other phenotypes? Consider Bateman’s principle:

Bateman’s principle is the theory that females almost always invest more energy into producing offspring than males, and therefore in most species females are a limiting resource over which the other sex will compete.

Female ova are energetically more expensive, and scarcer, than male sperm. Additionally, in mammals and other live-bearing species the female invests more time and energy after the point of fertilization but before the young exhibit any modicum of organismic independence (the seahorse being the exception). And, often the female is the “primary caregiver” in the case of species where the offspring require more care after birth. The logic of Bateman’s principle is so obvious when its premises are stated that it easily leads to a proliferation of numerous inferences, and many data are “explained” by its operation (in Mother Nature: Maternal Instincts and How They Shape the Human Species the biological anthroplogist Sarah Hrdy moots the complaint that the principle is applied rather too generously in the context of an important operationally monogamous primate, humans).

But the general behavioral point is rooted in realities of anatomy and life-history; in many dioecious species males and females exhibit a great deal of biological and behavioral dimorphism. But the direction and nature of dimorphism varies. Male gorillas and elephant seals are far larger than females of their kind, but among raptors females are larger. If evolution operated like Newtonian mechanics I assume we wouldn’t be theorizing about why species or sex existed at all, we’d all long ago have evolved toward perfectly adapted spherical cows floating in our own effluvium, a species which is a biosphere.

Going beyond what is skin deep, in humans it is often stated that males are less immunologically robust than females. Some argue that this is due to higher testosterone levels, which produce a weakened immune system. Amtoz Zahavi might argue that this is an illustration of the ‘handicap principle’. Only very robust males who are genetically superior can ‘afford’ the weakened immune system which high testosterone produces, in addition to the various secondary sexual characteristics beloved of film goers. Others would naturally suggest that male behavior is to blame. For example, perhaps males forage or wander about more, all the better to catch bugs, and they pay less attention to cleanliness.

But could there be a deeper evolutionary dynamic rooted in the differential behaviors implied from Bateman’s principle? A new paper in The Proceedings of the Royal Society explores this question with a mathematical model, The evolution of sex-specific immune defences:
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Fascinating post by Bayes, Phylogenetics, cultural evolution and horizontal transmission:

For some time now, evolutionary biologists have used phylogenetics. It is a well-established, powerful set of tools that allow us to test evolutionary hypotheses. More recently, however, these methods are being imported to analyse linguistic and cultural phenomena. For instance, the use of phylogenetics has led to observations that languages evolve in punctuational bursts, explored the role of population movements, and investigated the descent of Acheulean handaxes. I’ve followed the developments in linguistics with particular interest; after all, tracing the ephemeral nature of language is a daunting task. The first obvious road block is that prior to the invention of writing, the uptake of which is limited in geography and history, language leaves no archaeological record for linguists to examine. One particular note I’d like to make is that when Charles Darwin first formulated his theory of natural selection, he took inspiration from linguistic family trees as the basis for his sketch on the evolutionary tree of life. So it seems rather appropriate that phylogenetic approaches are now being used to inform our knowledge regarding linguistic evolution.

Like many other attempts applying evolutionary thinking in culture, phylogenetic approaches are, at times, met with contempt. This stems from assertions that cultural evolution and biological evolution differ greatly in regards to the relative importance of horizontal transmission….

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I guess the general points to take away from this post are: 1) Do not necessarily assume horizontal transmission is dominant in shaping culture; and, 2) Even with certain levels of reticulation, it does not necessarily invalidate a phylogenetic approach in investigating cultural and linguistic evolution.

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Earlier I pointed to the possibility of biophysical constraints and parameters in terms of inheritance shaping the local trajectory of evolution. Today Olivia Judson has a nice post [link fixed] on how the existence of two sexes in many species results in a strange metastable tug-of-war in terms of phenotypic evolution:

In sum, the traits that make a “good” male are often different from those that make a “good” female. (Note: I’m only talking about “good” in evolutionary terms. That means a trait that improves your chance of having surviving offspring.) Since many of these traits have a genetic underpinning, male and female genes are thus being sculpted by different forces.

But — and this is the source of the tension I mentioned — males and females are formed from the same underlying set of genes. After all, in humans, whether you’re a boy or a girl comes down to whether you have a Y chromosome or not: boys do, girls don’t. The rest of the genes occur in both sexes.

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I stumbled onto this New York Times Magazine The Brothers Emanuel, from 1997. Zeke, Rahm and Ari Emanuel have all become even more accomplished over the past 13 years. But I was surprised to discover that they had a younger sister, and that her life prompted the brothers to reflect on the influence of genetics and environment on life outcomes. Here’s the relevant portion:

Today, the brothers argue just as passionately about the role that environment and genetics played in the life of their sister, who in recent years has been on and off the welfare rolls that Rahm worked so hard to cut. Benjamin Emanuel met his daughter when he gave her a well-baby checkup and discovered that she had suffered a brain hemorrhage at delivery. The baby’s future was unclear; Shoshana’s birth mother, a young woman of Polish Catholic background, asked Dr. Emanuel if he knew someone who wanted her child. ”But I couldn’t find placement,” Benjamin Emanuel says. After a week of debate between both parents and sons – Marsha Emanuel had always wanted a girl – the Emanuels themselves took Shoshana in. ”What are you going to do?” Benjamin Emanuel says philosophically.

Intellectually, Shoshana developed normally – like her brothers, she graduated from New Trier, one of the most competitive high schools in the country – but she needed four operations and years of physical therapy to give her 85 percent use of her left side. She had a difficult adolescence, and today Marsha Emanuel, at the age of 63, is raising Shoshana’s two illegitimate children. (None of the Emanuels will talk about Shoshana in detail, and she declined to be interviewed for this article.)

The conversation the brothers continue to have about Shoshana is also, of course, a conversation about themselves. Were Zeke, Rahm and Ari simply successful products of Jewish middle-class parents who valued education and hammered them with expectations? How much of their drive came from their immigrant father? Certainly each Emanuel brother derives a large part of his identity that of the others. No one else, it seemed, mattered as much. ”The pressure is that you were judged by the family,” Ari says. ”Our family never cared about the kid down the block.”

Ari Emanuel also seems to have some opinions about I.Q.:
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I notice that not too many people seem to have switched from the old feed to the new. Part of the issue is that many people have subscriptions which they never check or have forgotten. But in case you’re reading this on the old feed, that’s because the techs are currently pointing the old feed to the new. But at some point this will not occur, and you’ll need the new feed. So if you haven’t, please switch to:

http://feeds.feedburner.com/GeneExpressionBlog

Danke.

(thanks to Edmund for reminding me)

Ed reviews a new paper on the fall of the Angkor civilization. He concludes:

Of course, a changing environment was far from the only reason behind the fall of Angkor. By the time the droughts kicked in, the city was already weakened by social, economic and political strife. Buckley simply thinks that the climate simply sealed the city’s demise. In fact, others have suggested that some force may have pushed the local people to move from inland agriculture to maritime trade. Buckley says that this transition coincides neatly with the aftermath of the first drought.

An economic historian might term the droughts which Angkor was subjected to an “exogenous shock.” Basically an outside factor which slams into an equilibrium system periodically (I assume that super-droughts would exhibit a poisson distribution but readers more climatically savvy can correct me). On the other hand, there are parameters which are endogenous to the system; consider the institutional frameworks which regulate social relations and distribute economic surplus.
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John Hawks has an excellent post rebutting some misinformation and confusion on the part of Colin Blakemore, an Oxford neurobiologist. Blakemore asserts that:

* There was a sharp spike in cranial capacity ~200,000 years ago, on the order of 30%

* And, that the large brain was not deleterious despite its large caloric footprint (25% of our calories service the brain) because the “environment of early humans was so clement and rich in resources”

Hawks refutes the first by simply reposting the chart the above (x axis = years before present, y axis = cranial capacity). It’s rather straightforward, I don’t know the paleoanthropology with any great depth, but the gradual rise in hominin cranial capacity has always been a “mystery” waiting to be solved (see Grooming, Gossip, and the Evolution of Language and The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature). Blakemore may have new data, but as they say, “bring it.” Until then the consensus is what it is (the hominins with the greatest cranial capacities for what it’s worth were Neandertals, and even anatomically modern humans have tended toward smaller cranial capacities since the end of the last Ice Age along with a general trend toward smaller size).

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Matt Yglesias muses on the possible influence of Isaac Asimove’s Foundation series on the way he looks at the world. Interestingly, Paul Krugman admits his debt to this series as well in getting him interested in economics. Unlike Robert Heinlein or mentor John W. Campbell Asimov was a political liberal. It is not uncommon for nerdy males, who are disproportionately represented in the pundit-class, to go through a science fiction phase in their youth. It would be interesting to see how interests in various authors tracked their current political positioning (I’d bet money that Poul Anderson is more popular with people who work at the Cato Institute).

Note: William Sims Bainbridge’s Dimensions of Science Fiction explores the various demographic trends which characterize the science fiction subculture. Politically there’s a bimodal distribution between liberals and libertarians, with more traditional conservatives such as Jerry Pournelle being the exception.

It is famously noted that when Charles Darwin published The Origin of Species he had no plausible theory of inheritance to drive his hypothesis. Specifically, one of the major issues of the “blending” model whereby the phenotypes of the parents average out in the subsequent generation is that such mixing eliminates the variation which is a necessary precondition for natural selection. At the same time that Darwin was revolutionizing our conceptualization of how the tree of life came to be, Gregor Mendel was preforming the experiments which solidified his eponymous theory of inheritance. Though ignored in his own day by ~1900 Mendelism reemerged and offered a relatively parsimonious abstraction which could explain why variation was not eliminated through the fusion of sexual reproduction. The discrete genes themselves were simply rearranged every generation in a digital manner, a genotype was translated into a phenotype, rather than the more analog model of phenotypic mixing which underpins a blending theory.* The fusion of genetics and quantitative evolutionary biology resulted in population genetics (see The Origins of Theoretical Population Genetics), while the cross-fertilization with ecology, natural history and paleontology eventually crystallized into what we would term the ‘Neo-Darwinian Synthesis’ by the middle of the 20th century.

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I am consciously aware that the “Idiot’s Guide” series are not parodies. But when Josh Roseneau introduced me to The Complete Idiot’s Guide to Understanding Intelligent Design I simply assumed that this was a parody or gag-gift. This illustrates the lack of unity of cognitive process. On the one hand as I note above I was aware of the reality that this was a well-known brand of introductory books, but my prejudice against Creationists and Intelligent Design folk, and my perception that they’re stupid, led to me infer reflexively that this was an ironic parody. After all, it seemed mean to point out that those looking to understand Intelligent Design may be somewhat duller, on average, than those who would find the enterprise laughable.
 
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A follow up to the post below, see John Hawks, Selection’s genome-wide effect on population differentiation and p-ter’s Natural selection and recombination. As I said, it’s a dense paper, and I didn’t touch on many issues.

Last week Nature published a paper which may have found a new ‘branch’ of the hominin evolutionary bush which may have been coexistent which modern humans and Neandertals. I recommend The Atavism, Carl and John Hawks on this story. Interesting times.

The following passage is from the epilogue of The Real Eve: Modern Man’s Journey Out of Africa by Stephen Oppenheimer:

In this book I have offered a synthesis of genetic and other evidence. Everything points to a single southern exodus from Eritrea to the Yemen, and to all the non-African male and female gene lines having arisen from their respective single out-of-Africa founder lines in South Asian (or at least near the southern exit). I regard the genetic logic for this synthesis as a solid foundation, and I have based the rest of my reconstruction of the human diaspora upon it. Obviously, the ‘choice’ of starting point (mine or theirs) determined all the subsequent routes our ancestors and cousins took. Tracing the onward trails is only possible as a result of marked specificity in regional distribution of the genetic branches The geographic clarity of both male and female gene trees is a big departure from the fuzzy inter-regional picture shown by older genetic studies. The degree of segregation of lines into different countries and continents is in itself good evidence that once they got to their chosen new homes, the pioneers generally stayed put, at least until the Last Glacial maximum forced some of them to move. This conservative aspect of our genetic prehistory also provides a partial explanation for the fact that when we look at a person, we can usually tell, to the continent, where their immediate ancestors came from, and underlies differences that some of us still call ‘race.’

Oppenheimer wrote the above in the early aughts, as his book was published in 2003. Much of this is generally in line with the ‘orthodoxy’ of the day. I believe that Oppenheimer’s assertion that there was one southern migration out of Africa by anatomically modern humans has gained some advantage over the alternative model of two routes, northern and southern, over the past ten years (Spencer Wells’ The Journey of Man sketches out the two wave model). Other assertions and assumptions have not stood the test of time. In particular, I would contend that generally the ‘conservative aspect of our genetic prehistory’ can no longer be taken for granted. Specifically, it seems likely now that much occurred after the Ice Age and during the Neolithic.

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Daniel Gross has a piece out on the rise of the cash economy, Cash Is King I found this section interesting, though not surprising:

…During the go-go years, it was common to hear theorists talk about the “discipline of debt.” On paper, high debt loads force managers (and homeowners) to make tough, swift decisions to stay solvent. Default, and you lose the company (or the house). But in reality, rather than scrimp, overextended borrowers are more likely to walk away from mortgages, or push companies into Chapter 11 bankruptcy protection. Americans are now discovering that cash exerts a superior discipline. The real discipline of cash may be that it causes executives, consumers, and investors to think twice—and to think about the long-term consequences—before spending. The need for instant gratification is part of what created the current mess.

There’s theory, and then there’s reality. I really don’t know if cash is so much better at enforcing discipline, but I’m sure theorists can invent a new rationale for why it is superior to debt financing in maximizing economic utility. Economic behavior is the most amenable in the social domain to theorizing, but too often it seems to fall prey to false certainty and after the fact rationalization of the status quote as the timeless equilibrium. This of course does not mean that we should not think logically, or deduce inferences from what we know a priori. Rather, in the social domain we should be extremely self-aware of our uncertainty as to the validity of our inferences based on the lessons of history. For example, there’s an obvious straightforward possible social consequence in regards to the spread of cash envelope usage, more break-ins. The greater utilization of relatively concrete paper currency* and its consequent drawbacks will probably make us more cognizant of the benefits of more abstract financial tools such as revolving credit card accounts (e.g., you lose cash, you’re screwed, you lose your credit card, you’re insured).

* Paper currency is itself a relatively new invention over the scope of human history

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