Racial differences in lifespan and reproduction.

Black Baby Girls More Likely To Live When Born Very Premature.

ScienceDaily (Jan. 4, 2006) — Black baby girls born weighing 2.2 pounds or less are more than twice as likely to survive as white baby boys born at the same weight, when many preemies are still too tiny to make it on their own, University of Florida researchers have found.
Analyzing data from more than 5,000 premature births, UF researchers pinpointed a link between gender and race and the survival rates of babies born at extremely low weights, according to findings released today (Jan. 3) in the journal Pediatrics. It’s the first scientific evidence of a phenomenon doctors have observed for years, said Steven B. Morse, M.D., M.P.H., a UF assistant professor of pediatrics and the article’s lead author.

Baby girls of both races had the strongest advantage when born weighing less than 1,000 grams, about 2 pounds or as much as a quart of milk, Morse said. Girls had nearly twice the odds of surviving as baby boys did, and black infants also had a slight survival advantage over whites, the research shows. Overall, black baby girls were twice as likely to survive compared with white baby boys, 1.8 times more likely to survive than black boys and 1.3 times more likely to live than white baby girls.

I can’t find the chart, but the premature babies with the worst chance of survival are East asian boys. I’m guessing that the Mongoloid gestation period might be a day or so longer than European based on that.

Gestation  term varies by race.

Obstetric outcomes may differ amongst ethnic groups when managed in the same setting. A British study found significant differences in duration and outcomes of labour when comparing white, Asian, and black women.Shorter gestational length has been observed in certain ethnic groups. Two studies have estimated an average gestational length 5 days shorter in black pregnancy.One study noted that differences were more strongly associated with the mother’s rather than the father’s race. Racial differences have also been observed in the rates of preterm (33–37 weeks) and very preterm (<33 weeks) birth in black compared with white women. A UK study explored the factors associated with preterm delivery in different ethnic groups and found that gestation was shorter in UK Africans and Afro-Caribbeans even after correction for socioeconomic risk factors.

One hypothesis for shorter average gestational length amongst black infants is that earlier maturation of the feto-placental unit relates to the maternal pelvic size. A smaller pelvis benefits the mother in evolutionary terms in relation to posture and stability when running. However, a smaller pelvis is also associated with a higher incidence of both obstructed labour and maternal mortality. Indeed, Africans have been observed to have amongst the highest emergency caesarean section rates. In fetal terms it is advantageous for the fetus to have a large head because of the improved brain growth. Thus, this creates conflict in the maternal/fetal relationship. It therefore would be in the interest of the fetus to mature faster and deliver earlier to avoid the complications described.

It is well recognized that gross motor skills develop in black infants earlier than in their white counterparts.12 There is also evidence of earlier fetal maturation. The incidence of the fetal passage of meconium during labour is strongly related to gestational age, increasing from less than 5% at 34 weeks in white European women, to over 25% post EDD.13 Black infants are significantly more likely to pass meconium in utero at all gestational ages, indicating earlier maturation.14,15

Perinatal mortality rates also differ amongst ethnic groups. Black infants in the US experience overall higher mortality compared with white infants.16,17 In the UK, the highest perinatal mortality rates have also been seen in ethnic minorities.18,19 However, this oversimplifies the relationship between perinatal mortality and ethnicity. Black gestational age specific mortality has been observed to be lower than white infants amongst those born preterm.17,19 After 37 weeks, this pattern is reversed with higher perinatal mortality amongst black infants compared with white infants.16 These observations suggest black infants mature earlier compared with white infants hence their survival advantage if born preterm. By contrast, black infants born after 40 weeks gestation may be susceptible to complications of post maturity at earlier gestations than white infants.

The aim of this study was to compare gestational length amongst three ethnic groups in nulliparous women with singleton pregnancies and spontaneous labour.

Full item here.  http://ije.oxfordjournals.org/cgi/content/full/33/1/10

It doesn’t mention it here, but there’s a lot of ‘first human wave’ Australoid ancestry in South Asia. I wonder if aborigines have a shorter pregnancy too.

 

Pygmies Evolved to Be Shorter Lived.

Pygmies are technically defined as groups of people whose men are, on average, shorter than 155cm (or 5 feet and an inch for the Imperial-minded). Strictly speaking, the word is restricted to several ethnic groups of African hunter-gatherers, like the Aka, Efe and Mbuti. But the world is surprisingly replete with shorter-than-average groups who also bear the colloquial moniker of pygmies, including some from Brazil, Bolivia, South-East Asia and Papua New Guinea.

Batwa pygmies in UgandaTogether with Lucio Vinicius and Marta Lahr, she found that the true pygmies grew slightly more slowly than the undernourished Americans, their growth spurts ended much earlier, at age 12 rather than 15. Typically, groups who lack free-flowing calories grow slowly over a long time – the pygmies’ pattern matched the first part but not the second. The pygmies’ growth curves disproved the malnutrition idea, but their lifespan pointed Migliano towards a better explanation.

Early death

Pygmies around the world are short in life expectancy as well as height, with the average adult dying at 16-24 years of age. Only 30-50% of children survive to the age of 15 and less than a third of women live to see menopause at 37. Taller African groups like the Ache or Turkana have lower adult mortality and twice the average lifespan, and compared to them, the pygmies’ pattern is closer to that of chimps.

Migliano argues that their early deaths are the driving force behind both their small size and their shorter growth spurts. It pays pygmies to divert resources away from growth and towards having children as early as possible, to compensate for their limited years. Indeed, Migliano found that they reach a peak of fertility earlier than taller groups.

James Eder, an anthropologist at Arizona State University in Tempe, collected data in the 1980s showing that Batak women reached menopause as early as 28 or 29 years old.

“The most distinctive thing I could say about [the Batak], other than the superficial things, is this business about a pop where women are shutting down their reproductive cycling,” Eder said. “I found cases of women 28 years old who said they no longer experienced menstruation. Very few births were occurring to women more than 30 years of age,” he said.

Eder allowed Migliano to use some of his data but did not participate in her research.

Racial differences in twinning rate.

 The standardized fraternal twinning rates are approximately 3.7, 6.6, and 9.7 per 1000 for Asians, whites, and blacks, respectively.

Overall twinning rate: 

For Nigerians, 1/20

For Europeans, 1/78

For East Asians, 1/150

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