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!