Saturday, November 24, 2012

Obama: White America's bogeyman?

Total fertility by race, 1980-2010 (source). Is the end of White America being hastened by the Obama presidency? Or is it actually being postponed?

Both the right and the left are trumpeting the Obama presidency as marking the end of White America. In a harshly worded column, conservative Ann Coulter argues that Obama and the Democratic Party are deliberately changing America’s demographics: 

If the same country that voted in 1980 had voted in 2012, Romney would have won a bigger landslide than Reagan did.

Most Americans don’t realize that, decades ago, the Democrats instituted a long-term plan to gradually turn the United States into a Third World nation. The country would become poorer and less free, but Democrats would have an unbeatable majority!

Under Teddy Kennedy’s 1965 immigration act, our immigration policy changed from one that replicated the existing ethnic population to one that strictly favored unskilled immigrants from the Third World. Since 1968, 85 percent of legal immigrants have come from what is euphemistically called “developing countries.” (Coulter, 2012)

Clearly, the 1965 immigration act was key to this demographic revolution. Just as key, however, were successive legislative changes, and increasingly lax enforcement, that progressively raised the levels of both legal and illegal immigration. Also key were differences in fertility rates. Non-White fertility stayed high long after White fertility had fallen during the 1960s and 1970s.

This demographic revolution, however, had the backing of both parties. Yes, the 1965 immigration act was ratified by a Democrat president, but it won the votes of most Republican lawmakers. Supporters included then congressman Gerald Ford (R) and then congressman Robert Dole (R). In fact, there was more opposition from Democrat lawmakers:

The House of Representatives voted 326 to 70 (82.5%) in favor of the act, while the Senate passed the bill by a vote of 76 to 18. In the senate, 52 Democrats voted yes, 14 no, and 1 abstained. Of the Republicans 24 voted yes, 3 voted no, and 1 abstained. (Wikipedia, 2012a)

After 1965, there came successive moves to increase the overall intake, and these moves were likewise Republican-backed. In fact, they were signed into law by Republican presidents. In 1986, Reagan proclaimed an amnesty that not only provided about three million illegal immigrants with citizenship but also set off a baby boom: 

Between 1987 and 1991, total fertility rates for foreign-born Hispanics increased from 3.2 to 4.4. This dramatic rise was the primary force behind the overall increase in the state’s total fertility rate during this period. Were it not for the large increase in fertility among Hispanic immigrants, fertility rates in California would have increased very little between 1987 and 1991. (Hill, 2002, pp. 27-28)

Bush Sr. signed into law the Immigration Act of 1990, which raised the annual legal intake of immigrants from 500,000 to 700,000 (Wikipedia, 2012c). And like his son, he declined to enforce sanctions against employers of illegal immigrants. By the time of Bush Jr., total immigration, both legal and illegal, was running at over one and a half million a year (Camarota, 2007). Far from ending illegal immigration, Reagan’s amnesty had set off a new wave of “undocumented workers” from south of the border. By 2007, the U.S. was home to an estimated 12.5 million illegal immigrants—more than four times the number that Reagan had amnestied (Wikipedia, 2012d)

Throughout this period, fertility rates continued to be much higher among America’s non-white minorities than in the majority White population. For whatever reason, Blacks and Hispanics were not participating in the economic and cultural changes that had reduced White fertility.

The other Obama revolution

The collapse of the Bush Boom led not only to the election of Barack Obama in 2008 but also to a sharp downturn in illegal immigration. Net illegal immigration may now be negative (Passel et al., 2012). Total immigration has fallen to levels unseen since the 1980s.

Non-White fertility has likewise fallen. Hispanic fertility in particular fell from a high of 2.86 children per woman in 2006 to 2.35 in 2010. The same period saw fertility declines in other population groups, with White Americans showing the smallest decline (Martin et al., 2012, see above chart). Preliminary data indicate that this convergence is continuing. In 2011, Hispanic fertility fell to the replacement level of 2.2:

[Fertility rates were] down 6 percent for Hispanic women and 2 percent for non-Hispanic black, whereas the rate for non-Hispanic white women was essentially unchanged. The GFR for AIAN [American Indian and Alaskan native] women was down 2 percent in 2011, whereas the rate for API [Asian and Pacific Islander] women rose 1 percent. The 2011 rates for non-Hispanic black and Hispanic women in 2011 were the lowest ever reported for the United States. (Hamilton et al., 2012)

If current trends continue, all of the major population groups will have fallen to about the same fertility rate by the time Obama leaves office. White Americans may even hold first place, their fertility being buoyed up by groups like the Mormons, the Amish, and the Hassidic Jews. Such a situation will be unprecedented in U.S. history.

One might object that these trends reflect the current hard times. True, but good times aren’t coming back any day soon. American economic growth will be sluggish for at least the next decade and any attempt to do better will abort spectacularly, like the end of the Bush Boom. Because the U.S. is now a mature economy, it can no longer grow at the rates we once saw during the postwar era and now see in many developing countries.

In addition, the decline in non-White fertility doesn’t seem to reflect only economic factors. Black American fertility was already falling during the 1990s and 2000s when economic conditions were much better, aside from a rise when Bush Jr. was pushing to expand minority home ownership. The same cultural factors that previously affected White fertility are now affecting all Americans, specifically a growing desire by women to marry later and limit their number of children.

What if a Republican had been in office?

Is this demographic reversal Obama’s doing? Would it have happened anyway? We can best answer these questions by asking what a Republican president would have done, like McCain in 2008 or Romney in 2012.

First, the level of legal immigration would have been raised—that was in Romney’s platform. Second, there would have been some sort of amnesty, not the same as Obama’s proposal but very similar number-wise. Some 12 million illegal immigrants would have become eligible for an “earned path to citizenship” and any children born on American soil would have automatically gained U.S. citizenship.

Third, there would have been efforts to spur another round of high economic growth through easy credit and deregulation, like the Bush Boom of the past decade.  Such a boom would have done little to raise the average worker’s wage, while doing a lot to spur another influx of low-wage labor for work in construction, agriculture, and services … to mow the lawns of the rich and to build them ever more monster homes.

Finally, a Republican president would have sought to limit access to abortion, perhaps even seeking to overturn Roe vs Wade. There would almost certainly have been a move to cut off Medicaid funding for abortion and birth control.


Regardless of what happens, White Americans are headed for minority status, but that process now promises to be longer and more drawn out than previously thought … thanks to the Obama presidency. Is this a case of his party naively acting against its own interests? Not really. Most Democrats aren’t “anti-White.” That’s a trope that certain dog-whistling Republicans are pushing. Most Democrats just want to see all Americans get the same deal—the same standard of living, the same quality of life, and the same freedom, including reproductive freedom.

Is that a naïve goal? Perhaps. But is it more naïve than the Republican goal of unlimited economic and demographic growth? If pre-2009 trends had continued, the U.S. population would have soared to almost half a billion by mid-century (Beck, 2010; Camarota, 2007).

Political choices aren’t always clear-cut. Yes, Romney is light-skinned, but that’s no guarantee that he cares about the future of White Americans. His interests coincide more with those of the corporate donors who keep the Republican Party afloat.  Yes, Obama is dark-skinned, but he may still be a better choice for White folks worried about their future.  To be sure, the Democratic Party is likewise influenced by corporate donors both directly and indirectly (via NPOs that are nonetheless corporate-funded), but it also has internal factions, like the union movement, that oppose the globalist project of outsourcing to low-wage countries and insourcing low-wage labor. Other factions, notably the environmentalists, are critical of unlimited growth. Finally, the different ethnic factions within the party don’t form a monolithic bloc; infighting will happen, and one faction or another will make appeals for support from White Americans.

Clearly, both parties leave much to be desired. In politics, however, one sometimes has to choose between the terrible and the less terrible. As White Americans descend to minority status, they will have to learn to live by their wits.


Anon. (2012). The USA’s Total Fertility Rates by Race, 1980 to 2010, Hail to you, October 7

Beck, R. (2010). Immigration by the numbers – off the charts,

Camarota, S.A. (2007). 100 million more projecting the impact of immigration on the U.S. population, 2007 to 2060, Centre for Immigration Studies

Coulter, A. (2012). Demography is destiny, Human Events, November 18, 2012

Hamilton, B.E., J.A. Martin, & S.J. Ventura. (2012).  Births: Preliminary Data for 2011, National Vital Statistics Reports, 61(5) October 3

Hill, L.E. (2002). Understanding the Future of Californians’ Fertility: The Role of Immigrants, Public Policy Institute of California, San Francisco

Martin, J.A., B.E. Hamilton, S.J. Ventura, M.J.K. Osterman, E.C. Wilson, & T.J. Mathews. (2012). Births: Final Data for 2010, National Vital Statistics Reports, 61(1) August

Passel, J., D. Cohn, & A. Gonzalez-Barrera. (2012). Net Migration from Mexico Falls to Zero—and Perhaps Less, Pew Hispanic Center, April 23

Wikipedia (2012a). Immigration and Nationality Act of 1965

Wikipedia (2012b). Immigration Reform and Control Act of 1986

Wikipedia (2012c). Immigration Act of 1990

Wikipedia (2012d). Illegal immigrant population of the United States

Saturday, November 17, 2012

The mysterious Ainu

Ainu men and Ainu woman, 18th century painting by Kodama Sadayoshi (source)

The Ainu of northern Japan have long been a puzzle. With their bushy beards, profuse body hair, large sunken eyes, and robust facial features, they look more European than East Asian. Yet genetic studies have shown no particular link to Europeans, at least no more than for East Asians in general: 

Omoto (1972, 1972) computed genetic distances among various populations of the world, and by constructing a phylogenetic tree he concluded that the Ainu population may have originated in East Asia, in spite of their unique morphological characters somewhat resembling West Eurasians. (Jinam et al., 2012)

This conclusion has been confirmed by a new study using close to a million single nucleotide polymorphisms. Genetically, the Ainu are closest to the Ryukyans, the inhabitants of Japan’s southernmost islands, and then to the Japanese themselves (Jinam et al., 2012).

So is the physical similarity to Europeans just a matter of chance? Convergent evolution? No, it may be that the Ainu have just not changed as much physically as other East Asians. They may thus preserve more of the original appearance that ancestral Eurasians once had before the last ice age split them into East and West Eurasians some 20,000 years ago (Rogers, 1986). This may also be why Kennewick Man (an ancient skeleton found in Kennewick, Washington and dated to 8410 BP) looks more like a European than a present-day Amerindian. Kennewick Man might have been closer to that proto-Eurasian population.

This point is sometimes hard to grasp. Real evolutionary change—the kind that shapes physical appearance—involves only a tiny fraction of the genome. The rest of the genome will change little in a new environment with a new set of selection pressures, either because it has little or no adaptive value (i.e., junk DNA) or because it has the same adaptive value in a wide range of environments.

So the evolutionary changes that made other East Asians look different from the Ainu involve relatively few genes. At other genes, the two groups are genetically indistinguishable. We likewise see genetic overlap between many sibling species that are nonetheless anatomically distinct. The same disconnect exists between genetic and anatomical data when we look at dog breeds … or human populations.

But why have the Ainu been so evolutionarily conservative? Why has time stood still for them? They probably didn’t undergo the severe selection pressures that shaped the appearance of other East Asians, notably selection for Arctic adaptations like the epicanthic eye-fold. Keep in mind that the Japanese archipelago enjoyed a relatively mild climate during the last ice age. As a “refugium” it did not impose the harsh selection pressures that mainland Asia imposed on its human populations. 


Jinam, T., N. Nishida, M. Hirai, S. Kawamura, H. Oota, K. Umetsu, R. Kimura, J. Ohashi, A. Tajima, T. Yamamoto, H. Tanabe, S. Mano, Y. Suto, T. Kaname, K. Naritomi, K. Yanagi, N. Niikawa, K. Omoto, K. Tokunaga, & N. Saitou. (2012). The history of human populations in the Japanese Archipelago inferred from genome-wide SNP data with a special reference to the Ainu and the Ryukyuan populations, Journal of Human Genetics advance online publication 8 November 2012; doi: 10.1038/jhg.2012.114

Omoto, K. (1972). Polymorphisms and genetic affinities of the Ainu of Hokkaido. Hum. Biol. Oceania, 1, 278–288.

Omoto, K. (1973). The Ainu: a racial isolate? Israel J. Med. Sci., 9, 1195–1215.

Rogers, R.A. (1986). Language, human subspeciation, and Ice Age barriers in Northern Siberia. Canadian Journal of Anthropology, 5, 11‑22.

Saturday, November 10, 2012

Are women changing color?

Tanned arm (source). Underarm skin color used to be a reliable measure of constitutive pigmentation (skin color before tanning). Is it still?

After puberty, girls become lighter-skinned than boys. This sexual differentiation has been shown to be hormonal in origin by a digit ratio study (Manning, Bundred, and Mather, 2004), by studies on normal, castrated, and ovariectomized individuals (Edwards & Duntley, 1939, Edwards & Duntley, 1949; Edwards et al., 1941), and by a twin study of boys and girls at different stages of puberty (Omoto, 1965). In addition, women are lighter-skinned than men in a wide range of human populations, although the sex difference is smaller in very light-skinned and very dark-skinned populations (Frost, 2007; Madrigal & Kelly, 2006).

This sex differences is reversed, however, in a recent study of subjects from Ireland, Poland, Italy, and Portugal: 

Surprisingly, we find in our cohort that males have lighter skin pigmentation (lower M) than females in all four European countries. (Candille et al., 2012)

All of the subjects were post-puberty (largely in their early to mid-20s) and the measurements came from the upper inner arm, a site relatively unaffected by tanning. So what happened?

First, a different kind of instrument was used to measure skin color:

Our results in populations of European ancestry contradict earlier anthropological studies that have concluded females are more lightly pigmented than males in most populations (reviewed in [2]). One potential reason for the conflicting results is the different instruments used. In early studies, which used the Evans Electric Limited (EEL) and Photovolt broad-spectrum spectrophotometers, skin pigmentation estimates may be confounded by the hemoglobin level to a greater extent than for the DermaSpectrometer used in the present study (Candille etal., 2012)

The Candille et al. research team didn’t measure skin color at all wavelengths of visible light. They focused on those wavelengths that melanin absorbs. Previous researchers had studied the overall visual difference between male and female skin, which is due as much to differences in hemoglobin as to differences in melanin. In short, men are browner and ruddier than women.

It is misleading, then, to state that the male subjects had lighter skin pigmentation. Hemoglobin too is a skin pigment.

Nonetheless, it’s still surprising that the women had more melanin than did the men, and this was on the upper inner arm—a body site relatively unexposed to tanning. That finding does contradict earlier studies. According to the earliest major one on human skin color:

It is generally known that women are lighter colored than men. From our studies it is apparent that this is due to the female skin containing less blood and melanin (Edwards & Duntley, 1939)

The study also found that this sex difference was smaller over much of the body surface, apparently because women exposed more of it to the sun:

The skin of women is generally poorer in melanin than that of men (fig. 16). However, because of their manner of dress, women of the white races show a comparatively higher pigmentation of the shoulders, upper chest and upper extremities (Edwards & Duntley, 1930)

For this reason, most subsequent researchers have measured skin color at the upper inner arm, this site being relatively unexposed to the sun and thus providing a better measure of constitutive pigmentation.

The study’s authors, Edwards and Duntley, went on to study castrated and ovariectomized subjects to understand how the sex hormones affect skin color. Although testosterone had a stronger impact than did estrogen on skin pigments (both melanin and hemoglobin), the absence of these hormones did not eliminate all of the sex-specific characteristics of male and female skin. The two researchers concluded:

Our observations show that ovariectomy does not entirely change the basic peculiarities which distinguish the female from the male skin. Similarly, the male castrates previously studied had maintained to some extent, their differences from the female. In both sexes, therefore, we can assert that sex differences are basically due to genic influence. This base line of pigmentary characteristics is then modified by the presence of the sex hormones. Unlike the situation in many other animals, where reactivity to the hormones is localized in special areas, the human skin reacts probably in its entirety (Edwards & Duntley, 1949)

This “genic influence” is now known to be the prenatal hormonal surge that determines whether an individual will develop as a boy or a girl. “Presence of the sex hormones” would be better described as “circulating sex hormones”—the individual’s current hormonal status. This is the conclusion of Manning, Bundred, & Mather (2004) in their digit ratio study:

We find that 2D:4D and female ‘constitutive’ pigment scores are negatively related. Since women with light skin tend to have high ‘feminised’ digit ratios, and there is evidence that the 2D:4D ratio is positively related to prenatal oestrogen levels, it seems that oestrogen may have an early organisational effect on skin pigment in women. The absence of a relationship between 2D:4D and skin colour in men suggests that other factors, such as prenatal testosterone, may obscure the in utero effects of oestrogen.

Other studies have focused on the sexual differentiation of skin color at puberty. All of them conclude that female skin loses melanin at puberty:

Though both the boys and the girls of the two populations show a decline in the melanin content of the skin when passing through adolescence, yet the decline in the pigment is so much pronounced in the girls that it reverses the sex differences in skin pigmentation. The boys, who were lighter in skin colour than the girls at younger ages (i.e. below 13 years), become darker than the girls at advanced age (at least up to 16 years) (Kalla, 1973).

In the above study, skin color was measured on the upper inner arm at a time of year (December-January) when tanning was minimal. Kalla (1973) concluded that the external environment could not have caused this sexual differentiation, the only possible explanation being “the puberty changes of the endocrine status.”

This was likewise the conclusion of Mesa (1983):

[…] the remarkable changes in pigmentation that occurred during the pubertal period (and which are related to hormonal changes) are a major factor in the differences (between the sexes and between the [upper inner] arm and the forehead) that were found at older ages and, also, in the differences observed in the adult population.

So how can we explain the recent findings by Candille et al. (2012)? Perhaps underarm skin color is no longer a reliable measure of constitutive pigmentation, i.e., color of untanned skin. Removal of underarm hair has become the norm in recent years, especially among European women. This has led to concern about tan lines in the underarm region and a consequent desire for “full body tanning,” as described below by one e-columnist:

How to Tan Underarms in a Tanning Bed

By Lauren Wise, eHow Contributor

A tanning bed provides a quick, easy, natural looking tan to a man or woman's body. The bed nearly triples your tanning time with the extra strong rays it provides. Unfortunately, since it is difficult to move around in a tanning bed, it is hard to tan every angle and crevice of the body, in particular the underarms. It is easy to change this by alternating your movements within the tanning bed throughout the session.


Candille, S.I., Absher, D.M., Beleza, S., Bauchet, M., McEvoy, B., et al. (2012). Genome-Wide Association Studies of Quantitatively Measured Skin, Hair, and Eye Pigmentation in Four European Populations. PLoS ONE 7(10): e48294. doi:10.1371/journal.pone.0048294

Edwards, E.A. & S.Q. Duntley. (1949). Cutaneous vascular changes in women in reference to the menstrual cycle and ovariectomy, American Journal of Obstetrics and Gynecology, 57, 501-509.

Edwards, E.A. & S.Q. Duntley. (1939). The pigments and color of living human skin , American Journal of Anatomy, 65, 1-33.

Edwards, E.A., J.B. Hamilton, S.Q. Duntley, & G. Hubert. (1941). Cutaneous vascular and pigmentary changes in castrate and eunuchoid men, Endocrinology, 28, 119-128.

File:Skin tanning.JPG

Frost, P. (2007). Comment on Human skin-color sexual dimorphism: A test of the sexual selection hypothesis, American Journal of Physical Anthropology, 133, 779-781.

Kalla, A.K. (1973). Ageing and sex differences in human pigmentation, Zeitschrift für Morphologie und Anthropologie, 65, 29-33.

Madrigal, L. & W. Kelly. (2006). Human skin-color sexual dimorphism: A test of the sexual selection hypothesis, American Journal of Physical Anthropology, 132, 470-482.

Manning, J.T., P.E. Bundred, & F.M. Mather. (2004). Second to fourth digit ratio, sexual selection, and skin colour, Evolution and Human Behavior, 25, 38-50.

Mesa, M.S. (1983). Analyse de la variabilité de la pigmentation de la peau durant la croissance, Bulletin et mémoires de la Société d'Anthropologie de Paris, t. 10 série 13, 49-60.

Omoto, K. (1965). Measurements of skin reflectance in a Japanese twin sample, Journal of the Anthropological Society of Nippon (Jinruigaku Zassi), 73, 115-122.

Wise, L. (2012). How to Tan Underarms in a Tanning Bed, eHow style

Saturday, November 3, 2012

Are the cads outbreeding the dads?

Whom will she choose? (source)
There has been much talk about two findings from a recent study: (a) boys reach puberty at different ages in different ethnic groups and (b) boys are reaching puberty earlier now than in the recent past.

The first finding is in line with previous studies:

[…] we found significant differences in the age of onset of stage 2 genital and pubic hair growth between African American boys as compared with white and Hispanic boys and transition to testicular volumes ≥4 mL (but not 3 mL). The meaning of this finding is unclear, as no existing studies inform differences in mean testicular size at given ages, by race/ethnicity, and sexual maturity stage; or in racial/ethnic differences in the rate of advancement through the Tanner stages over time. (Herman-Giddens, 2012)

The second finding is new:

We observed that onset of secondary sexual characteristics in US boys as seen in office practice appears to occur earlier than in previous US studies and the 1969 British study commonly used for pubertal norms. […] White boys in our study entered stage 2 genital growth 1.5 years earlier than the British boys (10.14 vs 11.60 years of age).
[…] These data are consistent with recent trends from other countries, such as Denmark, Sweden, Great Britain, Italy, and China. For example, urban Han Chinese boys achieve a testicular volume of ≥4 mL (13% by age 9) and spermarche earlier than studies conducted several decades ago; Danish boys achieve a testicular volume  ≥3 mL more than 3 months earlier now than 15 years ago. (Herman-Giddens, 2012)

The authors put the cause down to “exposure to chemicals, changes in diet, less physical activity, and other modern lifestyle changes and exposures.” In an article for CNN, the lead author elaborated:
"The changes are too fast," Herman-Giddes said. "Genetics take maybe hundreds, thousands of years. You have to look at something in the environment. That would include everything from (a lack of) exercise to junk food to TV to chemicals." (Wilson, 2012)

Yes, new genetic variants take time to appear through mutation. But variants for early puberty already exist in the population. Natural selection has only one thing to do: increase the proportion of people with those variants. And that can happen with each passing generation.

In any given population, almost all variability in male pubertal timing is genetic. This was the conclusion of a Swedish twin study: 

The heritability was 0.91 for age at onset of growth spurt and 0.93 for age at peak height velocity in this Swedish cohort of male twin pairs. Of interest is that these heritability estimates are almost the same as those reported from a Belgian twin study; that is, 0.93 and 0.92, respectively. Lower heritability estimates, 0.49 and 0.74, respectively, were found in a Polish twin study. (Silventoinen et al., 2008)

There is thus plenty of genetic variation for selection to act on. No need to wait for new mutations. But why would there be natural selection for earlier male puberty?

One reason is that early puberty is genetically linked to other sexual characteristics. In particular, a class of X-linked androgen receptor alleles is linked in males to aggression, impulsivity, sexual compulsivity, and lifetime number of sex partners and in females to paternal divorce, father absence, and early menarche (Comings et al., 2002). It is likely that these alleles also influence male pubertal timing, but research on this point is lacking—apparently because it is difficult to find a marker for pubertal maturation among boys that is as salient as age at menarche among girls (Ge et al., 2007). Early male puberty thus seems to be part of a “package,” or more precisely a reproductive strategy, that affects the way men go about finding a mate. Natural selection may favor one strategy or another, depending on the current cultural environment.

Is natural selection now favoring the “cads” over the “dads”? That might be what’s happening. As sexual relationships become less stable and shorter-term, women will ignore men who are oriented towards stable, long-term relationships.  This was the conclusion of a study directed by Kruger et al. (2003) at the University of Michigan's Institute for Social Research:

In the study, 257 women in college were asked to read passages from Scott's novels. Each read a paragraph describing a dark hero and one describing a proper hero. Then the women were asked which type of man they would prefer for a relationship.
As predicted by the cad-dad theory of human mating strategies, the women preferred the proper heroes for long-term unions. When asked which character they would like to see their future daughters choose, they also selected proper heroes. But when asked who appealed to them most for short-term affairs, the women turned to the dark heroes: the handsome, passionate and daring cads (Duenwald, 2003).


Comings, D.E., D. Muhleman, J.P. Johnson, & J.P. MacMurray. (2002). Parent-daughter transmission of the androgen receptor gene as an explanation of the effect of father absence on age of menarche. Child Development, 73, 1046-1051.
Duenwald, M. (2003). For a good time, well, don’t call dad, University of Nebraska-Lincoln, Anthropology, Raymond Hames

Ge, X., M.N. Natsuaki, J.M. Neiderhiser, & D. Reiss. (2007). Genetic and Environmental Influences on Pubertal Timing: Results From Two National Sibling Studies, Journal of Research on Adolescence, 17, 767–788.

Herman-Giddens, M.E., J. Steffes, D. Harris, E. Slora, M. Hussey, S.A. Dowshen, R. Wasserman, J.R. Serwint, L. Smitherman, & E.O. Reiter. (2012). Secondary sexual characteristics in boys: Data from the Pediatric Research in Office Settings Network, Pediatrics, 130, e1058-e1068.

Kruger, D.J., M. Fisher, & I. Jobling. (2003). Proper and dark heroes as DADS and CADS. Alternative mating strategies in British Romantic literature, Human Nature, 14, 305-317.

Silventoinen, K., J. Haukka, L. Dunkel, P. Tynelius, & F. Rasmussen. (2008). Genetics of pubertal timing and its associations with relative weight in childhood and adult height: The Swedish Young Male Twins Study, Pediatrics, 121, e885-891

Wilson, J. (2012). Boys – like girls – hitting puberty earlier, October 23, CNN