About This Project

“Evening men”, who go to bed and get up late, have more sexual partners and more extra-pair matings than “morning men”, who get up early and go to bed early. Evening people are often nicknamed "Owls", and morning people "Larks".

This is related to testosterone: evening types have a higher testosterone level. Does evening type signal good genes? To test this, we want to assess immunocompetence and sperm quality as surrogates of good genes and compare evening with morning types.

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What is the context of this research?

Men with high testosterone levels and a “later” sleep behavior have a higher mating success. We want to know if this is is this related to the good genes hypothesis.

https://en.wikipedia.org/wiki/...

Studies show relations between morningness and higher business (https://hbr.org/2010/07/defend...) and school success but also between eveningness and higher mating success (our previous study). But why is mating success higher in evening types? Is there a biological explanation? Is it related to evolution. Is it the "good genes"?

We want to assess surrogates of good genes and compare them between evening types and morning types. This will be set in relation with salivary testosterone as well as sleep behavior and a battery of questionnaires about sexual behavior.

What is the significance of this project?

These questions have never been tested before. We apply evolutionary theory (the good genes hypothesis) to human behavior. We try to emulate animal studies that showed relationships between testosterone, mating success and "good genes", but transfer the question to humans.

Three of our previous studies showed that this eveningness behavior is indeed related to a different sexual behavior.

When evening people have a higher mating success, this should be related to biological findings. So, the good genes might be an explanation. How can we test this? Good genes cannot be easily measured, so we need surrogates. Therefore, we measure sperm quality, testosterone and a marker of health.

We test correlations between eveningness and these measures.

What are the goals of the project?

We hope to get insight into the human mating system with a focus on sleep behavior (in the sense of morningness-eveningness) and to assess, if the higher mating success of evening types is related to their quality (health, sperm quality).

This work is of great interest. If we can show this relationship, we get new insights. Usually, morning people "rule the world" (http://www.standard.co.uk/life...), but the "winners" in evolutionary terms might be the evening people with a higher mating success.

This would show that different types (morning versus evening) have different profiles that are related to success in its widest sense.