We are researchers who work on sexual selection and mate choice. Ask us anything!
Hi Reddit! We are Tom and Ewan.
This AMA is part of #ImperialLates - free science events for all! Check out this week's programme here.
We are researchers at Imperial College London looking at how we choose our sexual partners and why - both as humans and in the animal kingdom. Our lab focuses on a number of topics across evolutionary biology and genetics, including mate choice in human and non-human primates, the evolution of sexual behaviour, speciation, and conservation genetics in various species
Do you resemble your partner and, if so, why?
Tom here. I work on human mate choice and explore patterns of 'assortative mating'. This is the tendency for mates to resemble one another in heterosexual and homosexual couples. Its occurrence is higher than would be expected under a random mating pattern. I ask why and I also look at the effect of this on reproductive outcomes. At the moment, I’m using a large database (Biobank) of around 500,000 people from the UK to answer two specific questions:
- First, I’m using the UK Biobank to test whether assortative mating is stronger in homosexual or heterosexual couples for socioeconomic, physical, and behavioural traits, but also for genetic ancestry (a more precise genetic measurement of what people usually call ethnicity). If there’s a difference, I’ll then try to understand why. This work is part of a wider series of projects being undertaken in my lab, headed by Vincent Savolainen, on the evolution of homosexuality in non-human primates.
- Second, I’m using genetic data from the UK Biobank to identify what we call “trios”, which are groups of three people containing two parents and their biological offspring. I’ll then look at whether the strength of assortative mating predicts reproductive outcomes for offspring, such as health in infancy and adulthood, or problems during pregnancy. The idea here is that matching for certain traits might increase parental genetic compatibility, ultimately helping offspring in various ways.
One of the overarching goals of these projects, especially the second one, is to explore ways in which natural selection might have affected assortative mating, offering some, albeit tentative, indication about whether we should expect the behaviour to occur in normal behaviour.
Sexual selection and evolutionary suicide
Ewan here. I’m an evolutionary geneticist and theoretician, and I build models that explore how choice in mates affects how populations evolve. We know that choice in mating partners affects the distribution of traits or characteristics in a population, so the evolutionary trajectories of many species are directly impacted by sexual behaviour. I use mathematical models to study this.
In particular, I look at the consequences of mate choice on genetic variation and population viability. For example, certain mating preferences in one sex can lead to the evolution of expensive traits in the other (such as colourful ornaments – think of a peacock’s tail). These traits can increase an individual’s mating success but at the expense of some other characteristic (such as the ability to avoid predation), which may lead to increased death rate and even extinction.
One class of sexual behaviours that have a particularly strong effect on population viability are those that generate ‘sexual conflict’. Because of their different reproductive biologies, males and females often favour very different strategies to maximise their fitness (ability to produce offspring). Sexual conflict arises when strategies evolve that are favourable in one sex but harmful to the other.
For example, in many species, males evolve behaviours which are harmful to females, such as harassment, or killing offspring sired by other males. These traits benefit males by coercing females into mating with them, thus increasing their own reproductive output, but simultaneously diminish that of the females they interact with. Clearly these kinds of behaviours have the potential to significantly reduce population viability because they decrease the total number of offspring that females can produce, and in extreme cases it is thought that male harm can become great enough to drive extinction – a case of ‘evolutionary suicide’!
However, the consequences of sexual conflict in populations can be very complex, as the existence of harming behaviours in males can favour the evolution of counter-adaptations in females, often called ‘resistance traits’, which mitigate the effects of male traits. In fact, one fascinating outcome of this can be a sexual “arms race”, as each sex sequentially evolves more and more extreme behaviours in order to overcome those evolving in the other!
Using mathematical models, I study how sexual conflict shapes which behaviours will be favoured by natural selection and the consequences of this for population demography, such as extinction risk.
Ask us anything! We’ll be answering your questions live 4-6PM UK time / 11AM-1PM Eastern time on Wednesday 10th February.
- Research on animal homosexuality and the bisexual advantage - https://www.imperial.ac.uk/news/190987/scientists-explore-evolution-animal-homosexuality/
- Overturning ‘Darwin’s Paradox’ - https://www.imperial.ac.uk/stories/overturning-darwins-paradox/
- Ewan Flintham’s Twitter page - u/EwanFlintham
- Tom Versluys’s academic homepage - https://www.imperial.ac.uk/people/t.versluys18