scholarly journals Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels around the time of conception

2007 ◽  
Vol 198 (1) ◽  
pp. 3-15 ◽  
Author(s):  
William H James
Keyword(s):  
Sex Ratios ◽  
Hormone Levels ◽  
Offspring Sex ◽  
Almost All

An attempt is made to summarize the evidence that the offspring sex ratios (proportions male at birth) of mammals (including man) are causally related to the hormone levels of both parents around the time of conception. Almost all of the cited studies were reported by non-endocrinologists. This being so, it would seem desirable to have comments of endocrinologists on this topic. The purpose of this article is to elicit such comment. Readers are requested to read the accompanying editorial (Clark & Davis 2008) to gain a better perspective of this hypothesis article.

Parental HLA Genes, Hormone Levels and Offspring Sex Ratios

1997 ◽  
Vol 47 (1) ◽  
pp. 60-60
Author(s):  
William H. James
Keyword(s):  
Sex Ratios ◽  
Hormone Levels ◽  
Hla Genes ◽  
Offspring Sex

FURTHER SUPPORT FOR THE HYPOTHESIS THAT PARENTAL HORMONE LEVELS AROUND THE TIME OF CONCEPTION ARE ASSOCIATED WITH HUMAN SEX RATIOS AT BIRTH

2008 ◽  
Vol 40 (6) ◽  
pp. 855-861 ◽  
Author(s):  
WILLIAM H. JAMES
Keyword(s):  
Breast Cancer ◽  
Hepatitis B ◽  
Present Note ◽  
Sex Ratios ◽  
Hormone Levels ◽  
The Past ◽  
Offspring Sex ◽  
Post Menopausal ◽  
Hormonal Treatments

SummaryDuring the past year, data have been published on the offspring sex ratios of people diagnosed with toxoplasmosis, hepatitis B, and pre- and post-menopausal breast cancer. It is shown here how these offspring sex ratios constitute further support for the hypothesis that mammalian (including human) parental hormone concentrations around the time of conception partially control the sexes of the resulting infants. If this interpretation were correct, then hormonal treatments might be considered for some or all of these conditions. It is intended that anyone who has read the present note and my two previous papers (James, 1996, 2004) should be aware of all the data relating to the hypothesis.

THE CATEGORIES OF EVIDENCE RELATING TO THE HYPOTHESIS THAT MAMMALIAN SEX RATIOS AT BIRTH ARE CAUSALLY RELATED TO THE HORMONE CONCENTRATIONS OF BOTH PARENTS AROUND THE TIME OF CONCEPTION

2010 ◽  
Vol 43 (2) ◽  
pp. 167-184 ◽  
Author(s):  
WILLIAM H. JAMES
Keyword(s):  
Causal Inference ◽  
Empirical Evidence ◽  
Sex Ratios ◽  
Nazi Germany ◽  
Hormone Levels ◽  
Offspring Sex ◽  
Firm Basis ◽  
Soviet Russia

SummaryThis note categorizes the evidence for the hypothesis that mammalian offspring sex ratios (proportions male) are causally related to the hormone levels of both parents around the time of conception. Most of the evidence may be acknowledged to be correlational and observational. As such it might be suspected of having been selected; or of having been subject to other forms of bias or confounding; or, at any rate, of being inadequate as a firm basis for causal inference. However, there are other types of evidence that are not vulnerable to these types of criticism. These are from the following sources: (1) previously neglected data from Nazi Germany and Soviet Russia; (2) fulfilled predictions; (3) genetics; and (4) a network of logically (mathematically) related propositions, for some of which there is overwhelming empirical evidence. It is suggested that this variety of evidence confers greater overall credibility on the hypothesis than would be the case if all the evidence were of the same observational/correlational status. This observational/correlational evidence is tabulated to illustrate its consistency.

Sequential alternation of offspring sex from successive eggs by female green anoles, Anolis carolinensis

2002 ◽  
Vol 80 (1) ◽  
pp. 77-82 ◽  
Author(s):  
Matthew B Lovern ◽  
Kelly M Passek
Keyword(s):  
Breeding Season ◽  
Sex Ratios ◽  
Female Offspring ◽  
Anolis Carolinensis ◽  
Sequential Alternation ◽  
Male And Female ◽  
Hormone Levels ◽  
Maternal Size ◽  
Offspring Production ◽  
Offspring Sex

We examined the relationships between maternal size, breeding season stage, and offspring sex at hatching for the oviparous lizard Anolis carolinensis. Specifically, we tested two hypotheses: (1) large females produce offspring with male-biased sex ratios and small females produce offspring with female-biased sex ratios; and (2) females, regardless of size, produce offspring with male-biased sex ratios early in the breeding season and female-biased sex ratios late in the breeding season. We found no support for either hypothesis. Rather, we found that individual females of all sizes and throughout the breeding season alternated offspring sex of sequentially laid eggs. Because female anoles also alternate the ovary that produces successive eggs, we tested a third hypothesis: females produce eggs of only one sex with each ovary. Both palpation to track which ovary produced which eggs, and unilateral ovariectomies, leaving females with only one functioning ovary, failed to support this hypothesis. Regardless of whether an ovary was removed, females were capable of producing both male and female offspring from either ovary. To account for this and potentially other unusual patterns of offspring production, we provide evidence that maternal hormone levels around the time of fertilization may affect offspring sex.

A new male-killing parasitism:Spiroplasmabacteria infect the ladybird beetleAnisosticta novemdecimpunctata(Coleoptera: Coccinellidae)

Parasitology ◽  
2006 ◽  
Vol 132 (6) ◽  
pp. 757-765 ◽  
Author(s):  
M. C. TINSLEY ◽  
M. E. N. MAJERUS
Keyword(s):  
Phylogenetic Analysis ◽  
Sex Ratio ◽  
High Efficiency ◽  
Sex Ratios ◽  
Egg Hatch ◽  
Hatch Rate ◽  
Male Killing ◽  
Offspring Sex ◽  
Novel Host ◽  
Males And Females

Whilst most animals invest equally in males and females when they reproduce, a variety of vertically transmitted parasites has evolved the ability to distort the offspring sex ratios of their hosts. One such group of parasites are male-killing bacteria. Here we report the discovery of females of the ladybirdAnisosticta novemdecimpunctatathat produced highly female-biased offspring sex ratios associated with a 50% reduction in egg hatch rate. This trait was maternally transmitted with high efficiency, was antibiotic sensitive and was infectious following experimental haemolymph injection. We identified the cause as a male-killingSpiroplasmabacterium and phylogenetic analysis of rDNA revealed that it belongs to theSpiroplasma ixodetisclade in which other sex ratio distorters lie. We tested the potential for interspecific horizontal transfer by injection from an infectedA. novemdecimpunctataline into uninfected individuals of the two-spot ladybirdAdalia bipunctata. In this novel host, the bacterium was able to establish infection, transmit vertically and kill male embryos.

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