Jois quotes:
Quoted message said:BJOG. 2003 Apr;110 Suppl 20:34-8. Links
Gender aspects of preterm birth.
Ingemarsson I.
Department of Obstetrics and Gynecology, University Hospital, Lund, Sweden.
Quoted message said:undifferentiated gonads formed either testes or ovaries. Studies in recent
Quoted message said:on the Y-chromosome is already transcribed at the 2-cell stage and triggers growth acceleration in
the XY embryos. This accelerated growth is believed to be important for the male embryo as it
allows complete testicular differentiation before the levels of oestrogenic hormones become too
high as pregnancy progresses. It is well known that the death rate is higher for male than for
female fetuses and that the increase is about 30% in chromosomally normal spontaneous abortions
(i.e. significantly higher than at birth). National figures from Sweden show that boys are more
likely to be delivered prematurely, accounting for 55-60% of all newborns between 23 and 32
gestational weeks. Neonatal deaths in these gestational weeks are also more common among boys. In
1993, the overall 1-year mortality rate (including all gestational weeks) in Sweden was 5.4% for
boys and 4.1% for girls. The difference in infant mortality (within 1 year) is most pronounced at
extremely early birth (23-24 gestational weeks) being 60% for boys compared with 38% for girls.
These are some of the most robust statistics in existence and were well-known in Darwin's time.
Indeed, he wrote the following in the "Descent of Man" (Chapter 8), with the last quoted paragraph
being the most important:
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In England during ten years (from 1857 to 1866) the average number of children born alive yearly was
707,120, in the proportion of 104.5 males to 100 females. But in 1857 the male births throughout
England were as 105.2, and in 1865 as
104. to 100. Looking to separate districts, in Buckinghamshire (where about 5000 children are
annually born) the mean proportion of male to female births, during the whole period of the
above ten years, was as 102.8 to 100; whilst in
N. Wales (where the average annual births are 12,873) it was as high as 106.2 to 100. Taking a still
smaller district, viz., Rutlandshire (where the annual births average only 739), in 1864 the male
births were as 114.6, and in 1862 as only 97.0 to 100; but even in this small district the
average of the 7385 births during the whole ten years, was as 104.5 to 100: that is in the same
ratio as throughout England.* The proportions are sometimes slightly disturbed by unknown causes;
thus Prof. Faye states "that in some districts of Norway there has been during a decennial period
a steady deficiency of boys, whilst in others the opposite condition has existed." In France
during forty-four years the male to the female births have been as 106.2 to 100; but during this
period it has occurred five times in one department, and six times in another, that the female
births have exceeded the males. In Russia the average proportion is as high as 108.9, and in
Philadelphia in the United States as 110.5 to 100.*(2) The average for Europe, deduced by Bickes
from about seventy million births, is 106 males to 100 females. On the other hand, with white
children born at the Cape of Good Hope, the proportion of males is so low as to fluctuate during
successive years between 90 and 99 males for every 100 females. It is a singular fact that with
Jews the proportion of male births is decidedly larger than with Christians: thus in Prussia the
proportion is as 113, in Breslau as 114, and in Livonia as 120 to 100; the Christian births in
these countries being the same as usual, for instance, in Livonia as 104 to 100.*(3)
Prof. Faye remarks that "a still greater preponderance of males would be met
birth. But the fact is, that for every 100 still-born females, we have in several countries from
134.6 to 144.9 stillborn males. During the first four or five years of life, also, more male
children die than females, for example in England, during the first year, 126 boys die for every 100
girls- a proportion which in France is still more unfavourable."* Dr. Stockton-Hough accounts for
these facts in part by the more frequent defective development of males than of
than the female; and variations in important organs would generally be injurious. But the size of
the body, and especially of the head, being greater in male than female infants is another cause:
for the males are thus more liable to be injured during parturition. Consequently the still-born
males are more numerous; and, as a highly competent judge, Dr. Crichton Browne,*(2) believes, male
infants often suffer in health for some years after birth. Owing to this excess in the death-rate of
male children, both at birth and for some time subsequently, and owing to the exposure of grown men
to various dangers, and to their tendency to emigrate, the females in all old-settled countries,
where statistical records have been kept,*(3) are found to preponderate considerably over the males.
Na. Stark also remarks (Tenth Annual Reports of Births, Deaths, &c., in Scotland, 1867, p. xxviii.)
that "These examples may suffice to show that, at almost every stage of life, the males in
Scotland have a greater liability to death and a higher death-rate than the females. The fact,
however, of this peculiarity being most strongly developed at that infantile period of life when
that the higher male death-rate is an impressed, natural, and constitutional
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Diploid heterogamy in mammals (XY males) is a very mild form of haplodiploidy, but the phenomenon
does put the heterogametic gender at some greater informational risk than the homogametic gender.
Whatever defects lie on the nonredundant X in males are expressed without hope of correction by a
"backup" copy residing on a now absent homologous chromosome.
There is also good evidence to support the contention that males have been evolved to be more
universally fragile and more error expositive than their conspecific females. Males in most metazoan
species succumb more readily than females to disease, trauma, exhaustion and starvation; suffer
higher embryonic
bear generally higher parasitic worm loads; live shorter lives or are driven from the population
after breeding, occasionally dying synchronously. Polygynous males rarely care for their young, thus
they become especially dispensible to the population in times of ecological stress and may be
actively discriminated against during such periods.
Male excess mortality in some mammals appears to be directly and programmatically derived from
androgenic hormonal levels, especially testosterone. Castrated human males live on average 13.6
years longer than unmodified men. Similarly, in feral Soay sheep (Ovis sp.), wether lambs (castrated
males) significantly outlive both ewe and ram lambs. In contrast, mortality in normal males due to
(aggressive, combative) masculine behaviours
normal rams 5:1. The loss of gonads not only markedly alters the aggressive nature of the males but
also diminishes behaviours that would otherwise promote high levels of physiological and
nutritional stress.
In contrast, in the birds, heterogamety is reversed. It is the female who now has an unpaired
chromosome (WZ) and is the gender who is put at greater informational risk. The effect of this
informational reversal appears to have
easily seen in the data taken from wild populations that appears at:
As mammalian populations age, the percentage of males drops. The pattern is precisely reversed in
birds. As birds age, the percentage of females decline and we are left with conclusion (using
Darwin's words) "that the higher female
alone."
Wirt Atmar
