She's BAAAACK!!!

Some of you might have noticed that Gene Expression’s Spanish gypsy has been AWOL for a few months. I was cramming for finals March until May, and now I’m slogging through my math and science requirements. Anyway, I’ll still post from time to time. Here’s a brief one because I have math class tonight (AAAAAUUUGHHH!)

The Washington Post is waxing a la Book of Revelation about Cali’s budget crisis. Here’s the Post’s analysis:

” As in many other states, the shortfall is largely the result of the national economic downturn — which has been especially severe in Silicon Valley, an engine of California’s $1.3 trillion economy. Soaring health care costs for the poor and new expenses for homeland security are other contributing factors. Republicans here also contend that Davis, who was narrowly elected to a second term in November, has spent recklessly while in office and relied on accounting gimmicks to balance the budget last year.”

Gee, who do you think the poor could be? For most of my life, poor has been the polite term for ghetto blacks. Is the vocabulary of political correctness changing so that poor now means penniless, functionally illiterate Mexican illegal immigrant? Or will poor simply be anyone who with the rotten luck to be born on the wrong tail of the Bell Curve? I invite the etymological musings of all Gene Expressors.

Update from duende: Anyone notice the author’s surname? No wonder she’s hesitant to finger Latin American illegals as a budget drain.

Comment from Razib: As David has noted on the message board, the main reason for California’s budget shortfall is the high-IQ bureaucratic elite in Sacramento. “The poor” are in fact usually just tools, proximate elements, in the ultimate well being of the bureaucratic class.

Update from Godless: A few comments:
-I find the tone of this post unnecessarily pejorative. Unskilled illegal immigration *is* a big problem – but it is a problem caused by the mainly white businessmen who hire illegal immigrants under the table, by the mainly white mandarinate in Sacramento (as Razib commented), by the mainly white INS and Border patrol, and by the mainly white amnesty-dangling administration. Change the attitudes of those in power and you change illegal immigration. The Spanish-surnamed do not have this sort of power.

-I’m uncomfortable with the idea that ethnicity trumps all when it comes to balanced reporting – certainly there’s no shortage of non-Hispanic reporters that would softpedal the immigration data. Another point – we’re not sure whether the reporter’s family came in legally or illegally. As reported by Steve Sailer, those immigrants who’ve come in legally tend to oppose illegal immigration, because of understandable opposition to further wage competition. Finally, seeing as duende herself is of (European) Spanish ancestry (and likely has a Spanish surname)…shall we disregard her posts on the grounds of her surname alone? Unless she takes an ideological position to our liking, that is…

Addendum from Razib: Camille-err, I mean duende, is I believe black Irish….

What was M.E.?

My post about Mitochondrial Eve attracted a bunch of interest – thank you! – and several people asked a key question: what species was ME?

There is no direct evidence about ME at all – we have not found a fossil record of this particular individual.  We can infer logically that she must have existed, and we can deduce approximately how long ago she lived from the amount of variation in Mitochondrial DNA (mtDNA) among present humans – about 200,000 years ago.  This analysis also indicates the probable region in which she lived – East Africa.

From the age and region, we can deduce the species, see the following timeline:

modern human family tree

As you can see, homo heidelbergensis was the direct ancestor species for homo sapiens.  This species has been further divided into homo sapiens archaic and home sapiens modern; a distinction made based on recent fossil finds.  The earliest human skulls were recently found in Ethiopia, dated about 160,000 years ago.  ME was most likely homo sapiens archaic, although based on this date and region, it is possible she was an early homo sapiens modern.  [ thanks to Dennis O’Neil for the diagram ]

One fascinating point to make in this connection is that there is never a “first organism” for any species.  Much like ME itself, the crown of “earliest organism” for a species is retrospective, since speciation takes place over thousands of years and can only be discerned gradually.  The classic definition of species – organisms which can interbreed – is not as cut and dried as one would like; there are often cases where A can breed with B, and B can breed with C, but A cannot breed with C.

It is interesting to speculate on the early history of ME and her ancestors.  Was there a catastrophic event which eliminated many of ME’s competitors, funneling the genetic ancestry through a single line?  Perhaps ME migrated into a region which was spared from a climatic or other environmental event.  Or perhaps ME embodied a mutation which conferred immunity from a particular disease.  ME’s daughters and granddaughters might have followed a single evolutionary path, living together in the same region and contributing to a common gene pool.  Or perhaps one or more daughters split off, forming subspecies which ultimately died out.

The transition period from H. sapiens archaic to H. sapiens modern is about 50,000 years, or about 250,000 human generations.  Although that seems like a lot, this is actually a short timescale from an evolutionary standpoint.  The genetic changes over this period would be slight.

It is suggestive that ME apparently lived right at the earliest time where the fossil record indicates the transition from H. sapiens archaic to H. sapiens modern.  The family tree for ME must have contained thousands of branches which did not successfully make it to the present day, although we know from the very definition of ME that it does contain at least two which did!

Buy a spouse


  Bridewealth payment Inheritance system
Mating system No Yes Even Sons favored
Monogamy 62% 38% 42% 58%
Limited Polygyny 46% 53% 20% 80%
General polygyny 9% 91% 3% 97%
  Nonstratified Stratified
Society Polygynous Monogamous Polygynous Monogamous
Dowry Absent 624 99 263 45
Dowry present 1 2 5 27

I just bought John Alcock’s Animal Behavior for $5 at a used book store here in Montpelier (see my review of Triumph of Sociobiology by the same author). I was flipping through and found these tables in the chapter titled The Evolution of Human Behavior.

Alcock states that “bride-price,” the practice of the groom’s family paying that of the bride, occurs in societies where there is a shortage of women because wealthy men aquire many wives. In contrast, dowry tends to occur where there is a premium on high status males, in other words, societies where monogamy is enforced and even wealthy males are limited to one wife, who therefore gains all the accrued benefits. 66% of societies surveyed in the Ethnographic Atlas had some form of brideprice, while only 3% practiced dowry (the monogamous upper caste Hindu culture is the most famous of these). Also note that societies in with men can aspire to multiple wives tends to skew inheritance patterns-because sons are a far better investment in terms of returning grandchildren to the parents (at least among those with wealth to give!), while monogamous societies have more balanced reproductive outcomes and therefore patterns of giving to children of both genders.

Mitochondrial Eve

Of all the women who have ever lived, there was one woman who was special.  She was the common maternal ancestor of all women currently alive.  She was “Mitochondrial Eve”.

Consider the set of all women who have ever lived.  Each had exactly one mother.  Now shrink the set of all women to contain only mothers.  Each of them had exactly one mother.  Shrink the set again to contain only mothers of mothers.  Again, each of these women had exactly one mother.  Again, shrink the set to contain only mothers of mothers of mothers.  Continue doing this until you have a set with exactly one woman.  She is the maternal ancestor of all living women; she is Mitochondrial Eve.

We don’t know much about ME.  We do know that she had at least two daughters.  If she didn’t have any daughters she couldn’t be ME, and if she had only one daughter then her daughter would be ME.

mitochondriaThe reason this woman is called Mitochondrial Eve is interesting and significant.  Inside all living cells are structures called Mitochondria, which function as the “power sources” for the cell.  Evolutionary biologists believe that mitochondria were originally separate organisms similar to bacteria, which were “captured” by cells long ago.  Mitochondria have their own DNA, separate from the cell’s DNA.  All animals inherit their mitochondria and their mitochondrial DNA solely from their mother.  So Mitochondrial Eve is the sole ancestor to a long line of successful mitochondria, and her mitochondrial DNA (mtDNA) is found in all living humans.

Interestingly, geneticists believe that ME lived as recently as 200,000 years ago, based on the observed variation in mitochondrial DNA found in present-day humans.

When ME was alive, she was almost certainly not “the ME”.  There would have been other women alive at the same time who would have had different female ancestors.  It is only retrospectively, as a function of the women alive today, that ME is “the ME”.  Furthermore, in the future she may again no longer be “the ME”; the entire female line of one of her daughters may die off, leaving one of her daughters or granddaughters or great-granddaughters or … with the title.

I find it fascinating that it is logically provable that ME existed.  You may too, or you may be thinking “so what?”  But aside from being an interesting concept, akin to “the tallest living man”, what else about ME is interesting?  Well, the fact that mtDNA is inherited solely from one parent makes it a simple and interesting way to track variations in human populations.  It is both easier and more accurate than measuring variations in cell DNA.  Assuming that mtDNA mutates with a relatively consistent rate, and given that all living humans had one common mtDNA ancestor (ME), then measuring the average difference between mtDNA samples taken from human populations is a good way to measure the “evolutionary distance” between them.

mtDNA does not necessarily mutate with the same frequency as cell DNA, in fact, most human geneticists feel it probably mutates far less frequently, both because it is genetically “old”, and because it only reproduces by fission, leaving less opportunity for “crossing over”.  mtDNA therefore provides an interesting “fixed timeline” for comparing potential mutations and mutation rates in cell DNA.

I should mention that some have argued that mtDNA need not mutate with a relatively consistent rate, due to technical reasons involving the mechanisms of mitochondria formation within cells.  If it doesn’t it would make mtDNA variation less useful in genetic studies, but it would not mean there was no ME, contrary to arguments others have advanced.

Mitochondria are essential structures in cells, providing as they do the chemical machinery for generating energy.  We can surmise that at one time there was tremendous selective pressure on mtDNA, leading to the present high peak in the valley of fitness.  Because all living humans have a recent common ancestor, they all have similar mtDNA and similar mitochondrial function, and hence there is little selective pressure.  There is evidence to suggest differences in mitochondria may result in differences in human aging.  This would be an important finding if true, leading to much fruitful research, but would not affect selection in the slightest; what is important in selection is how many children you have and when you have them, not how long you live after you have them…

Other than satisfying the definition given above, what was special about ME?  Well – nothing!  She was in all likelihood an unremarkable woman, not especially different from her contemporaries in any significant way.  Her coronation as ME owes as much to luck as to genetic fitness or any other factor.  But just think how much the course of history would have changed had some accident befallen her!  This is the butterfly effect in evolution 🙂

{By a similar argument, there was one man who was Y-chromosome Adam, the common male ancestor of all men who are alive today…  It is astronomically unlikely that ME and YA were contemporaries, and even more unlikely that they knew each other or mated together.}

[ This post owes much to Daniel Dennett’s classic book, Darwin’s Dangerous Idea. ]

Comment from Razib: In Y: The Descent of Man the biologist Steve Jones asserts that of the tens of thousands of knights listed in The Doomsday Book (circa 1100) none has left a titled male descendent today.

Brights?

Richard Dawkins is trying to form some sort of movement to get atheists or non-theists called ‘brights’. His explanation:

A triumph of consciousness-raising has been the homosexual hijacking of the word “gay”. I used to mourn the loss of gay in (what I still think of as) its true sense. But on the bright side (wait for it) gay has inspired a new imitator, which is the climax of this article. Gay is succinct, uplifting, positive: an “up” word, where homosexual is a down word, and queer, faggot and pooftah are insults. Those of us who subscribe to no religion; those of us whose view of the universe is natural rather than supernatural; those of us who rejoice in the real and scorn the false comfort of the unreal, we need a word of our own, a word like “gay”. You can say “I am an atheist” but at best it sounds stuffy (like “I am a homosexual”) and at worst it inflames prejudice (like “I am a homosexual”).

Paul Geisert and Mynga Futrell, of Sacramento, California, have set out to coin a new word, a new “gay”. Like gay, it should be a noun hijacked from an adjective, with its original meaning changed but not too much. Like gay, it should be catchy: a potentially prolific meme. Like gay, it should be positive, warm, cheerful, bright.

Bright? Yes, bright. Bright is the word, the new noun

I don’t know whether he was off his rocker when he wrote this. I mean, I’m pretty smug about my scientific materialism too, but this sort of campaign makes us non-theists look like dweebs, really. But if you’re interested, here is the website. I wouldn’t mind getting into this for networking purposes and I don’t even disagree with the outreach objectives, but why such a smug name? It makes us look like … Christian evangelists.

FREUDIAN SLIP

There was an error in my note on ‘Family Connections’.

The novelist daughter of Lucian Freud is Esther Freud, not Bella Freud. Bella is a fashion designer.

For British readers, there is a profile of Esther in today’s Telegraph magazine. It mentions that the novelists Rose and Susie Boyt are Esther’s half-sisters. I’m not sure if they have the same mother or same father – Lucian Freud had (possibly still has) a very tangled love life.

Enough of Freuds already!

DAVID BURBRIDGE

Posted by David B at 04:23 AM

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Implications of chromosomal sex determination

Razib’s recent entry on the erosion of the Y chromosome got me thinking: what advantages does this method of sex determination have that allow it to persist despite the ongoing problem of Y chromosome deterioration? A little research suggests that it may help us mammals make larger evolutionary jumps than would be possible for other classes of vertebrates, which use other methods of determining sex (birds also use chromosomes for sex determination, but more on them later). To begin with, see here for a discussion of a recent Y-chromosome mutation that may have led to the creation of modern humans as a separate species. The paper also goes into some detail on how mutations of the Y chromosome provide a mechanism for evolutionary saltation that overcomes some of the objections raised by the gradualists.
This has interesting consequences. It implies that mammalian and bird evolution could follow the model of punctuated equilibrium while other creatures might be (mostly) stuck with gradual evolution.
Birds, however, have homogametic males (where humans and mammals in general have heterogametic males). As a result the risks associated with mutations to the non-recombining sex chromosome fall first on the females of the species, and consequently the costs are higher. Birds would seem therefore less able to make large evolutionary leaps, and I would guess that the amount of genetic variation throughout the class of birds (10,000 species or so) is less than that found in mammals (4,000 species). Examination of the phenotypes seems to support this idea.
Another question this raises is whether creatures must be able to manifest some minimal rate of species change or else risk extinction. There are a number of features that a species can have that allow for rapid mutation and selection:
– a large number of descendants (which also implies rapid elimination of bad variations)
– a short time interval between successive generations
– imperfect DNA replication mechanisms to increase various sorts of error rates
– the Y chromosome mechanism described above

Since mammals and birds don’t do well in the first two categories, and can’t afford the third feature given their investment in their young, I would guess that the development of their method of sex determination was a necessary precursor to the high-K reproductive strategies they use. Without it, the speciation or evolution rate for a high-K species would fall too low, and we would not have seen the great bursts of adaptive radiation that the mammals have shown.

Don't be too smart

The Executioner’s I.Q. Test is an article in The New York Times on IQ & the death penalty. Check this out:

For the court majority, and for organizations like the American Association on Mental Retardation, it is clear that mentally retarded people should be exempt from the death penalty because, as a group, they are prone to gullibility and have poor impulse control and limited abstract-reasoning abilities, all of which render them less responsible for their actions — or at least for their death-penalty crimes.

Does this mean that those in the top 3%, IQs above 130, should be held to a different standard? A higher standard for mitigating circumstances? 😉

POPULATION FALLACIES: PART 2

This is about birth rates.

The crude birth rate is the number of births per head of the population in a given period, usually a year. It is an objective statistic, and it is useful for some purposes, but it is seriously affected by the age structure of the population.

To avoid this problem what is usually quoted as the ‘birth rate’ is the Total Fertility Rate. This is the number of children that a women would have in her
reproductive life if at any given age she had the same fertility as an average woman of that age at present.

For comparative purposes the TFR is less misleading than the crude birth rate, but it is not sufficiently understood that the TFR can also be misleading in its own way. It is a statistical construct based on the experience of a heterogeneous population of women over a short period of time. It does not measure the fertility of any actual cohort of women in the past, and it does not accurately predict the fertility of any actual cohort of women in the future.

One problem is that the TFR will fluctuate according to temporary circumstances, such as economic recession. If in a particular year women are less likely to have babies because of (say) economic uncertainties, then the TFR may fall sharply, but it is likely to bounce back. More seriously, if there is a long term trend for women to have babies at a different stage of their reproductive life, this will distort the TFR upwards or downwards, and it may take a decade or more for the true picture (the actual lifetime fertility of a cohort of women) to become clear. Notably, if women are postponing having babies from their twenties to their thirties, this will immediately reduce the TFR, but the TFR will eventually rise again when they have the babies they postponed earlier.

So, for example, when you read that the TFR in Japan has fallen to 1.3, this doesn’t necessarily mean that any cohort of Japanese women will on average only have 1.3 children. Maybe they will, maybe they won’t, but at least part of the fall in the TFR is likely to be a temporary distortion due to a time-shift in the pattern of child-bearing.

TFRs for immigrant groups can also be very misleading, as they are often constructed out of the fertility experience of women of different ages, partly in their country of origin and partly in the host country, under different demographic regimes.

I’m not suggesting that TFRs are useless, just that it is important to understand their limitations.

DAVID BURBRIDGE

Move over Matt Ridley

About the author of the evol. psych. book Dr. Tatiana’s Sex Advice:

Olivia Judson is an evolutionary biologist and award-winning science journalist. She received her doctorate in biological sciences from Oxford University before joining the staff of The Economist, where she wrote about biology and medicine. She is presently a research fellow at Imperial College in London. [her undergraduate degree is from Stanford -Razib]

And now check this out….

Total package….

Listen to her here being interviewed about the book (type “Judson” under the guest text box).

Well, it seems looks matter when it comes to pop science. Remember Spencer Wells, author of The Journey of Man, why was it him in particular that emerged out of Stanford’s human population genetics lab?

Posted by razib at 03:39 PM

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