When males are not needed - 6 Minute English

Hello. This is 6 Minute English

from BBC Learning English.

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 - the

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.

But what type of animal was

Flora? Was she:

a) a python?, b) a zebra shark?,

or c) a Komodo dragon?

Hmm, 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, colonise 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

colonise 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 summer,

both female and male aphids

hatch out and start to

reproduce by mating.

So the aphids have the

best of 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 maximise 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) 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!