Rapid responses are electronic comments to the editor. They enable our users
to debate issues raised in articles published on bmj.com. A rapid response
is first posted online. If you need the URL (web address) of an individual
response, simply click on the response headline and copy the URL from the
browser window. A proportion of responses will, after editing, be published
online and in the print journal as letters, which are indexed in PubMed.
Rapid responses are not indexed in PubMed and they are not journal articles.
The BMJ reserves the right to remove responses which are being
wilfully misrepresented as published articles or when it is brought to our
attention that a response spreads misinformation.
From March 2022, the word limit for rapid responses will be 600 words not
including references and author details. We will no longer post responses
that exceed this limit.
The word limit for letters selected from posted responses remains 300 words.
Hansen et al[1] raised a number of interesting issues. It is
unfortunate that space did not permit a review of the many phenomena
thought to lead to a small change in the sex ratio. These include diseases
such as prostatic cancer (more sons) and non Hodgkin's lymphoma (more
daughters).[2] Occupation also seems to lead to a change in the sex ratio
with doctors producing more sons than the rest of the population and
ministers of religion producing more daughters.[2] These findings have
been linked to the hormonal status of the parents which in turn has been
used by evolutionists to construct a theory linking social status in the
ancestral environment with the desired sex ratio of children for long term
reproductive success[3] We must be aware however that the flexibility of
evolutionary theory may undermine its credibility.[2]
Since the discovery of the effect of hormonal status on the sex ratio
of offspring there has been vigorous debate as to whether this is likely
to be a pre or post conception effect. Hansen and his colleagues leave
this point open, but if their data is taken at face value then it provides
evidence for a post conception effect. If periconceptual life events occur
in the first trimester then they have a greater effect on the sex ratio
than at any other time, with only 40.6% boys amongst the offspring. Stress
in the first trimester would seem to lead to the preferential loss of male
foetuses, presumably through spontaneous abortion. As the authors have
pointed out it is still possible that some of these stresses began before
the first trimester.
A limitation of the study is uncertainty in regard to the status of
the father, in terms of paternity and consequently in terms of paternal
stress around the time of conception. The sex of offspring is partially
controlled by the hormonal status of both parents. This is a substantial
loss of data.
An assumption made is that recorded life events correlate closely
with biological stress. In this linkage study only hospital related life
events were included but work and marital stresses are other
possibilities.[4] There may also be individuals who come through life
events without being physiologically stressed. Blood markers such as
testosterone or cortisol would therefore be helpful.
Colin Dewar
S.H.O. at the Crichton Royal Hospital,
Bankend Road,
Dumfries DG1 4TJ
1 Hansen D, Moller H, Olsen J. Severe periconceptual life events and
the sex ratio in offspring. British Medical Journal 1999;319:548-9.
2 James WH. The Hypothesised Hormonal Control of Mammalian Sex Ratio at
Birth - A Second Update. J. Theor. Biol. (1992) 155, 121-128. - Parental
Hormone Levels and the Possibility of Establishing that some Mammalian Sex
Ratio Variation is Adaptive. J. Theor. Biol. (1989) 140, 39-40.
3 Ridley M., 1993, The Red Queen, Penguin Books, London.
4 Hilgard ER, Atkinson RL, Atkinson RC. Introduction to Psychology, 7th
Edition, Harcourt Brace Jovanovich, Inc.
Response
Hansen et al[1] raised a number of interesting issues. It is
unfortunate that space did not permit a review of the many phenomena
thought to lead to a small change in the sex ratio. These include diseases
such as prostatic cancer (more sons) and non Hodgkin's lymphoma (more
daughters).[2] Occupation also seems to lead to a change in the sex ratio
with doctors producing more sons than the rest of the population and
ministers of religion producing more daughters.[2] These findings have
been linked to the hormonal status of the parents which in turn has been
used by evolutionists to construct a theory linking social status in the
ancestral environment with the desired sex ratio of children for long term
reproductive success[3] We must be aware however that the flexibility of
evolutionary theory may undermine its credibility.[2]
Since the discovery of the effect of hormonal status on the sex ratio
of offspring there has been vigorous debate as to whether this is likely
to be a pre or post conception effect. Hansen and his colleagues leave
this point open, but if their data is taken at face value then it provides
evidence for a post conception effect. If periconceptual life events occur
in the first trimester then they have a greater effect on the sex ratio
than at any other time, with only 40.6% boys amongst the offspring. Stress
in the first trimester would seem to lead to the preferential loss of male
foetuses, presumably through spontaneous abortion. As the authors have
pointed out it is still possible that some of these stresses began before
the first trimester.
A limitation of the study is uncertainty in regard to the status of
the father, in terms of paternity and consequently in terms of paternal
stress around the time of conception. The sex of offspring is partially
controlled by the hormonal status of both parents. This is a substantial
loss of data.
An assumption made is that recorded life events correlate closely
with biological stress. In this linkage study only hospital related life
events were included but work and marital stresses are other
possibilities.[4] There may also be individuals who come through life
events without being physiologically stressed. Blood markers such as
testosterone or cortisol would therefore be helpful.
Colin Dewar
S.H.O. at the Crichton Royal Hospital,
Bankend Road,
Dumfries DG1 4TJ
1 Hansen D, Moller H, Olsen J. Severe periconceptual life events and
the sex ratio in offspring. British Medical Journal 1999;319:548-9.
2 James WH. The Hypothesised Hormonal Control of Mammalian Sex Ratio at
Birth - A Second Update. J. Theor. Biol. (1992) 155, 121-128. - Parental
Hormone Levels and the Possibility of Establishing that some Mammalian Sex
Ratio Variation is Adaptive. J. Theor. Biol. (1989) 140, 39-40.
3 Ridley M., 1993, The Red Queen, Penguin Books, London.
4 Hilgard ER, Atkinson RL, Atkinson RC. Introduction to Psychology, 7th
Edition, Harcourt Brace Jovanovich, Inc.
Competing interests: No competing interests