I'm Neil.

And I'm Rob.

Do you think there are big differences between men and women, Neil?

Apart from the old stereotypes we sometimes hear

like, that men can't express emotions...

I suppose biologically

there are differences, Rob.

I mean, men and women's bodies are different.

Right, and it takes both a man and a woman to make a baby.

Well, that's true, in humans anyway.

But in this programme

we'll be hearing about creatures in the wild,

where the classic 'boy meets girl' love story doesn't apply.

Yes, we'll be meeting some female animals who don't need a male to make babies.

These creatures reproduce by parthenogenesis,

also called virgin birth.

This is the process where the female can reproduce without a mate,

a term used for an animal's sexual partner.

All animal species survive by making babies,

reproducing to make copies of themselves.

But amazingly,

the female of some species can do it all by herself!

But before that, it's time for my quiz question.

In Britain's Chester Zoo in 2006,

Flora laid eleven eggs that developed into healthy babies.

Her zookeepers were mystified

because Flora had only been kept with other females and had never been near a male.

What type of animal was Flora?

Was she a) a python, b) a zebra shark,

or c) a Komodo dragon?

Pythons are pretty unusual creatures,

so I'll say Flora was a python.

OK, Rob, we'll find out later if you're right.

Actually, it's not only reptiles who behave this way.

The females of many animal species are able to reproduce without sex.

By doing this they gain several advantages:

they can rapidly spread, colonize and control large areas,

and they don't waste time and energy looking for a mate.

But if a world without sex is so much better,

why bother with males at all?

Good question, Neil,

and one which BBC World Service programme, Discovery, asked evolutionary biologist, Chris Wilson.

Well, absolutely!

And there are other advantages,

I mean, if you're an all-female population,

you don't have to waste time searching and competing for mates,

there are no more sexually-transmitted diseases

and so it seems like the easiest decision

and yet,

less than one percent of all animal species are completely celibate,

and that's a huge fundamental puzzle in evolutionary biology

that we're still not entirely sure we understand

it's called sometimes the paradox of sex.

Despite the advantages of going without sex,

in reality fewer than one percent of all animals are celibate - live without having sex.

This begs the question,

why is sex so common when it seems so inefficient?

Chris calls this the paradox of sex.

A paradox is a situation which seems contradictory because it contains two opposite facts.

For example, the existence of males if we can reproduce without them.

As a male myself,

I have to say I'm feeling a little underappreciated right now, Rob!

Well, don't worry, Neil,

because it turns out there might be a use for males after all!

It seems the sex paradox has been solved by one of nature's most ingenious insects - aphids.

Here's ecologist, Amber Wright,

explaining how to the BBC World Service's Discovery programme.

See if you can hear the strategy American aphids use to reproduce.

The aphids we have in the US,

when spring comes around,

the eggs hatch and they'll be all female for several generations,

and then at the end of the summer,

they will hatch out males and females and mate,

and then create eggs that wait for next year,

kind of the best of both worlds.

Hedging their bets basically,

using cloning to rapidly colonize

and then using sex to mix up the genes.

In the spring, female aphids lay eggs which hatch,

break open, allowing the young to come out.

The young aphids that hatch are all female.

But later, at the end of the summer,

both female and male aphids hatch out

and start to reproduce by mating.

So, the aphids have the best of both worlds,

they enjoy the advantages of very different things at the same time.

Or to put it another way,

the aphids hedge their bets.

They follow two courses of action

instead of choosing between them.

By cloning themselves with 'virgin births' and reproducing sexually,

aphids maximize their chances of survival.

Gardeners around the world will be upset to hear that

those young aphids just love eating tomato plants!

But on the plus side,

it seems being male can be useful after all.

But not if you're Flora,

the female you asked about in your quiz question.

So, what type of animal was she?

Right, I asked whether the virgin Flora was...

a) a python, b) a shark

or c) a Komodo dragon.

I guessed a python.

Well, Rob, you're right that some female pythons can reproduce by themselves,

and sharks too.

But the correct answer is that

Flora was c) a Komodo dragon.

OK, let's recap the vocabulary,

starting with mate, an animal's sexual partner,

something you don't have if you're celibate - living without sex.

Animal eggs hatch or break open to let the young out.

And a paradox is a situation which seems contradictory

because it contains two opposite facts.

Species which reproduce parthenogenetically and sexually have the best of both worlds -

enjoy the advantages of very different things at the same time.

And if you hedge your bets,

you follow two courses of action instead of choosing between them so you don't miss out.

Well, that's all there's time for. Bye for now! Goodbye!