Carole Hooven, Ph.D.

So I got interested in testosterone because this is one thing I could grab onto that links very clearly humans, chimpanzees, every other mammal in terms of males having much higher levels than females.

And it's not just mammals.

There are other forms

of steroid hormones that other species have, but this is pervasive and just a very powerful way to understand proximately, that means what's happening here and now in the organism, why the sexes are different.

And then there are these deep evolutionary pressures that have to do with reproductive strategies

for organisms that produce sperm versus organisms that produce eggs.

And so then I ended up reapplying to Harvard and getting into the grad program there.

And I did my dissertation on testosterone and sex differences in cognition.

the way we think and process information and I had men watch sexy videos and also videos of dental surgery and collected their saliva and measured their testosterone in the lab and then I just stayed on at Harvard mostly just teaching.

So vertebrates, most vertebrates will have testosterone or something very, very close to testosterone.

Yep.

So sharks I don't know about specifically.

First of all, males are not always bigger than females.

Males will do whatever they need to do generally to compete for mates.

And in many species, it's not to be larger.

Also, there are differences in the ability to defend a territory or defend mates in air and water and land.

And that's really an interesting way to understand some male competitive strategies.

But generally, when...

In the species, if the female is just as aggressive, often it's maternal aggression and not necessarily mate competition.

Maternal aggression tends to be mediated more by estrogen than testosterone, even in hyenas, which are...