Why Y Chromosomes Might Disappear

Is it possible that Y Chromosomes might actually disappear from genetic code? What would happen to species as we know them? We're generally taught that chromosomes determine an animal's sex, but turns out, it is way more nuanced than that. Learn what's going on in this new episode of SciShow, hosted by Rose Bear Don't Walk!

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Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever:

Chris Peters, Matt Curls, Kevin Bealer, Jeffrey Mckishen, Jacob, Christopher R Boucher, Nazara, charles george, Christoph Schwanke, Ash, Silas Emrys, Eric Jensen, Adam, Brainard, Piya Shedden, Alex Hackman, James Knight, GrowingViolet, Sam Lutfi, Alisa Sherbow, Jason A Saslow, Dr. Melvin Sanicas, Melida Williams
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Sources:

[uplink-on-yt]

My Y chromosome isn't small. It was just cold, that's all.

[xeros]

i swear, platypus was just a beta test enviroment for random traits, that somehow made it to live build by mistake.

[arcaneusumbra]

Bold of everyone to assume we'll still be human as we know it by that time

[danielmetcalf]

"On top of being semi-aquatic, egg-laying mammals of action..." is a nice little Perry the Platypus easter egg you laid there ❤️

[kurczaczak]

Traveling ten thousand years in the future would be fascinating. Traveling ten million years in the future would be terrifying

[PJoriginal]

I'm surprised they didn't talk about animals like clownfish who can change sex on the fly. IIRC If the female dies, the male changes into a female

[zenmart]

I remember hearing once that “if there is one thing the history of evolution has taught us it's that life will not be contained. Life breaks free, it expands to new territories and crashes through barriers, painfully, maybe even dangerously, but, well, there it is.”

[Planet-of-the-Gibbons]

Thanks. I had heard about this Y Chromosome disappearing thing, and like many people with low knowledge on biology, I thought it meant the extinction of human males in the far future! Misconceptions need good explanations like this to go away.

[Viewer]

"Sex that develops based on temperature"
This gives a whole new meaning to "You're hot" and "We're cool"

[ZeusTheIrritable]

Are we certain that the platypus wasn't dropped here by some alien civilization just to troll us?

[vegatwice]

Humanity has a knack for predicting wrong things with too much confidence

[Ming]

A platypus, something that god decided to make instead of a griffon. God: Hmm, eagle/lion... Naw let's just make Duck/beaver.

[kcoovi]

Imagine being the last guy with an XY chromosome meanwhile, everyone else around you moved to a new sex-determination system

[coldsobanoodle]

There is another interesting species that has lost the Y chromosome in males known as the Amami spiny rat. Of course they have a different sex determining factor in place in the absence of SRY from the Y chromosome.
In males there is a gene that turns on zinc finger proteins in order to turn the undifferentiated gonads into testes.

[dreyhawk]

Two other interesting genetic setups are 1) several aquatic creatures change sex when needed, like Clownfish where each school is headed by a matriarch. When she dies the dominant male changes to female and takes her place. And 2) Some reptiles reproduce without contributions from a partner. Mourning Geckos are especially known for this as there are no males at all. The gecko reproduces by Parthenogenesis. It's been seen in some other lizards and some snakes. This is why I love science! There are so many variables and permutations. It never gets boring!

[arga]

Fun fact, if a XY human is missing the SRY gene they develop as a female and they are able to give birth, completely indistinguishable form other XX females
However if an XX human gains the SRY gene they develop as a male however they are infertile because the production of sperm is encoded in different genes within the Y chromosome, which they don't have.
EDIT: There seems to be some confusion, XY humans who lack an SRY gene are not hermaphrodites, transgendered, futanari etc.
They are indistinguishable from XX females, your own mother could be XY and you would never find out unless she got a DNA test. This is because all the information to become a women is in their X chromosome.

[Gaston-Melchiori]

I love that you put the sources in the description. Very few people do.

[starshine]

So basically….the Y chromosome won’t be around forever but will be around for at least many thousands of years because it would take that long for the Y chromosome to evolve smaller and smaller until it disappears.

[XENOXTA]

As someone with two Y chromosomes, genetics and it’s variation across animal species never ceases to amaze me.

[XenXenOfficial]

"Yo doctor I've had 6 girls, I want a boy. Could you help me out?"
"Aw-yeah dude. It's gotta be that right nut. See like.... I'm pretty sure the right one makes boys. If we remove the left one, the only option is to have a boy."
"Sounds 'bout right."