Why Do Some Animals Change Sex?

CrowdScience

BBC

Science

4.8 • 1K Ratings

🗓️ 31 August 2018

⏱️ 28 minutes

🔗️ Recording | iTunes | RSS

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Summary

In humans if you have two X chromosomes you are female and if you have an X and a Y then you are male. It is textbook science. But CrowdScience listener Du in Singapore has done some extra homework and found a piece of intriguing fish research which suggests a different outcome, at least for one species – tilapia, a popular fish on restaurant menus worldwide and as it happens, the first fish to visit space. Whilst humans couldn’t exist without an X-chromosome, tilapia apparently, can. In fact, they are happy with just two Y chromosomes. The existence of this odd breed comes down to the tilapia fish’s ability to change from male to female. Nature has come up with an array of bizarre solutions when it comes to sex determination and what sets you on one genetic path or another. And like with the tilapia fish, the decision isn't always for life. Some species of fish, lizards and even birds sidestep the chromosome system and morph between the sexes to survive a changing environment. How can they have both genetic sex pathways latent within them? And why can’t humans do the same trick?

Presenter: Marnie Chesterton

Producer: Louisa Field

(Photo: A male Asian sheepshead wrasse courting a female featured in BBC’s Blue Planet II. Credit: Getty Images)

Transcript

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0:00.0	Take some time for yourself with soothing classical music from the mindful mix, the Science of
0:07.0	Happiness Podcast.
0:08.0	For the last 20 years I've dedicated my career to exploring the science of living a happier more meaningful life and I want
0:14.4	to share that science with you.
0:16.1	And just one thing, deep calm with Michael Mosley.
0:19.4	I want to help you tap in to your hidden relaxation response system and open the door to that
0:25.5	calmer place within. Listen on BBC Sounds. This is crowd science from the BBC World Service. I'm Marnie Chesterton.
0:36.0	This week we're taking another bite out of a topic we've visited before.
0:40.0	Sex. But this time it's with a twist.
0:44.0	Last year we made a crowd science episode about why we have males and females.
0:52.0	And as we made that program we came across some
0:55.2	intriguing animals that have the ability to alter their sex and we wanted more.
1:01.2	So on this episode prepare to meet the super male tilapia fish.
1:05.6	We had headlines, sex discrimination that can feed the third world. No sex
1:12.4	please be growing in the Sunday times. Super male
1:15.6	farm fish could feed millions daily telegraph. You know this was a really big
1:19.9	story at the time. And dive into the ocean for a fishy situation.
1:26.2	Her head expands and her chin gets longer.
1:38.0	A she has changed into a he. The question that originally set us on a journey of sexual discovery was sent in by listener do in Singapore.
1:45.0	He really wanted to know about a curious asymmetry in the system that makes us humans male or female.
1:52.0	Every baby is made of an ex-chromosome from the egg, from the mother.
1:57.0	The other half of your DNA is delivered by a sperm.
	...

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