Dave Hone

So there's a branch of sexual selection called mutual sexual selection, and the black swans are an example of this.

The classic sexual selection is, yeah, your peacocks and your lions and things like this.

Males are bigger and more flamboyant and whatever it is, and they're doing all the competing.

But you get mutual sexual selection, and this is really common in a whole bunch of things that people are familiar with but don't know.

Loads of seabirds.

Starlings, the common starling that we have in Europe and has been introduced into the US.

Parrots, various other things where basically males and females invest similarly in rearing the offspring.

And so the idea generally, both with Handicap and Sexy Son, but particularly with Handicap, is the idea is the males are proving their worth.

They're basically saying, I'm the biggest, strongest, healthiest.

I've got the best genes.

I should be the father of your offspring.

They go around showing off and then mate with as many females as possible, while the females then do all the work and make the nest and look after the chicks or rear them or give birth or whatever it may be.

Yadda, yadda, yadda.

And so the idea with mutual sexual selection is, well, what if there's not much food around?

Things like puffins, penguins in the Arctic, where the male sits with the egg and the female toddles off, gets food, and then comes back two months later or whatever it is.

On their own, they can't rear the offspring.

They have to have a male investment.

Well, now...

suddenly the male's now putting loads of effort in.

So the male's now in the same position that a female would be in under the normal conditions.