Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Male or female?

22.09.2015

According to a well-known theory in evolutionary biology healthy females should give birth to more males than females. A study funded by the Swiss National Science Foundation shows why this is not always true.

According to popular belief, whether you have a baby girl or boy is purely a matter of chance. And yet, a study published several years ago shows that mothers in stressful jobs, for instance, give birth to more girls than boys.

The correlation between such shifts in the offspring sex ratio and the mother’s overall state is something that evolutionary biologists are familiar with from other animal species. One influential hypothesis puts natural selection as an explanation for the imbalances observed.

Strong males with high reproductive success

The Trivers-Willard hypothesis states that it is beneficial for mothers to be able to adjust the sex of their offspring in response to their own state of health. Accordingly, a female in good condition should give birth to more male offspring.

This is because successful males have the potential to produce more children in their lifetime than successful females. By producing strong sons, healthy mothers increase the probability of their own genes being widely distributed. Conversely, low-ranking females who are not in such good shape are more likely to produce daughters, because the chances of giving birth to a future dominant male are poor.

“However, it’s not quite as simple as that,” points out biologist Peter Neuhaus sponsored by the Swiss National Science Foundation, based at the University of Calgary in Canada. Taking the example of a model with data from Columbian ground squirrels and Canadian bighorn sheep, Neuhaus – together with colleagues from the UK, the US, France and South Africa – has demonstrated in an article published in Nature magazine that optimal reproduction also depends on a series of other factors.

Dead before reaching sexual maturity

Bighorn ewes, for instance, give birth to only one lamb a year. Most females mate with the dominant ram, which means many of the other males don’t get a chance. Females in a good state often pass on their condition and so can be expected to “to make supermales”, as Neuhaus explains.

Nonetheless, the healthy females do not produce more male than female offspring. As the model demonstrates, other parameters, such as the fact that a large number of males die before reaching sexual maturity, play a central role in assessing reproductive potential.

But what have sheep got to do with mothers in jobs with some degree of stress? Nobody doubts that they have more girls, but Neuhaus advises caution: “Evolution is very complex. To understand how it works, you need to take into account as many factors as possible that could influence reproductive potential.”

(*) S. Schindler, J.-M. Gaillard, A. Grüning, P. Neuhaus, L. W. Traill, S. Tuljapurkar & T. Coulson (2015). Sex-specific demography and generalisation of Trivers-Willard theory. Nature online: doi:10.1038/nature14968

(Available for journalists as a PDF file from the SNSF: com@snf.ch)

Contact persons

Prof. Peter Neuhaus
Department of Biological Sciences
University of Calgary
Calgary, AB, T2N 1N4, Canada
Tel.: +1 403 220 8776
E-mail: pneuhaus@ucalgary.ca
Time difference: -8 hours

Dr. Susanne Schindler
Institut für Evolutionsbiologie und Umweltwissenschaften
Winterthurerstrasse 190
CH-8057 Zurich
Tel.: +41 76 295 36 85
E-mail: susanne.schindler@zoo.ox.ac.uk

Weitere Informationen:

http://www.snf.ch/en/researchinFocus/newsroom/Pages/news-150921-press-release-ma...
https://sschindlerblog.wordpress.com/2015/09/21/daughter-or-son-which-sex-to-pro... Susanne Schindler’s blog

Medien - Abteilung Kommunikation | idw - Informationsdienst Wissenschaft

More articles from Life Sciences:

nachricht Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory

nachricht How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>