What is up with Rosharan genetics?

[Mason Wheeler]

Several of the humans on Roshar display slightly inhuman physical traits, such as Thaylen eyebrows or Herdazian fingernails, but possibly the most bizarre thing of all is the hair.  It's said that a full-blooded Alethi will have pure black hair, but one who has mixed with other races of humanity will have other hair colors mixed in, in exact proportion to their racial lineage.

 

That's so incredibly weird I don't even know where to start.  Suffice it to say, Mendelian inheritance does not work like that!  (When's the last time you saw a biracial person with two natural hair colors?)

 

Do we have any official explanation of what in the world is going on with genetic inheritance on Roshar?  Because it obviously doesn't work in the same way as it does on Earth, and yet the humans there are supposed to be... well.. human.

[Oversleep]

Herdazian fingernails are due to human-Listener interbreeding.

But it's getting weird again. Why? Because Horneaters are also a result of such interbreeding and they display different features than Herdazians.

Edited April 15, 2016 by Oversleep

[Eki]

Hair in particular seems to be very significant in the Cosmere. Take Warbreaker's Royal Locks for example. They are only passed down through the Idrian royal line - never to people who aren't potential heirs. (exactly how that's determined... who knows)

[Erunion he/him]

There appear to be two native races on Roshar, the Aimians and the Listeners/Parshendi, both of whom are more 'cognitive' than humans. 
Humans appear to be a non-native species, that was brought to the world (likely by Honour/Cultivation). 

 

Frost in the letter implies that Roshar was designed specifically by Adonalsium (whereas, say, Scadrial was a combined effort between Ati and Leras). So it's likely He was having fun creating new species, ecology, and everything. 

 

Herdazians, Horneaters, and possibly some others are the result of interbreeding between Humans and Listeners/Aimians. 

 

What I'm curious about, is what's up with the hair. Alethi have Jet black hair, and Iriali have GOLDEN hair. Both stand out from 'lesser' hair colours, and both breed true in a way that other hair colours don't. Could the Iriali have been 'Cultivations' race, and the Alethi 'Honours race'? A group of people who were archetypical of their shard and who the Shards marked with hair colour? 

 

And that's not even mentioning Amber, Violet and other weird eye colours. 

EDIT: Or what's going on with lighteyes/darkeyes. Because the mechanics of Heterochromia on Roshar do not match those on Earth, which implies that Something Is Up. 

Edited April 15, 2016 by Erunion

[Oversleep]

This post (and links in it!) answers some of the issues talked about here (but none of the questions of the OP).

[ecohansen]

That's so incredibly weird I don't even know where to start.  Suffice it to say, Mendelian inheritance does not work like that!  (When's the last time you saw a biracial person with two natural hair colors?)

 

Corn.  Barbara McClintock, transposons, and corn

 

 

Well, either that or mosaicism.

[Argent he/him]

Suffice it to say, Mendelian inheritance does not work like that!  (When's the last time you saw a biracial person with two natural hair colors?)

 

Good ol' Mendel could actually work, it's the hair pigmentation genes that seem weird.

 

Now that I think about it, we've seen this type mixed coloration in at least one place in our world - cat fur. If I recall correctly, the reason cats have stripes of differently colored fur is because the gene that determines the color is a sex-linked chromosome, and (and here I am skipping some science I don't remember well) during the embryo's development some of its cells end up with the father's copy of the gene (and so, if they end up being responsible for producing fur, will produce it in the same color as the father), and some end up with the mother's copy (and will color likewise). Mendelian genetics has no issue with this.

 

So it's possible - and I wouldn't be very surprised if it so - that the gene(s) that code for hair color in the Alethi - or maybe all Rosharans? - get bundled on a sex-linked chromosome. I don't see why that would be the case, unless Adonalsium (or some Shard(s)) decided it would look cool, but it's at least possible.

[IndigoAjah he/him]

Several of the humans on Roshar display slightly inhuman physical traits, such as Thaylen eyebrows or Herdazian fingernails, but possibly the most bizarre thing of all is the hair. It's said that a full-blooded Alethi will have pure black hair, but one who has mixed with other races of humanity will have other hair colors mixed in, in exact proportion to their racial lineage.

That's so incredibly weird I don't even know where to start. Suffice it to say, Mendelian inheritance does not work like that! (When's the last time you saw a biracial person with two natural hair colors?)

Do we have any official explanation of what in the world is going on with genetic inheritance on Roshar? Because it obviously doesn't work in the same way as it does on Earth, and yet the humans there are supposed to be... well.. human.

As most things are not monogenic but polygenic, and there is significant splicing involved in meiosis and fertilisation, with plenty of epigenetics and dormant genes, actually if the genes for hair colour etc happened to be formed in a certain manner aligned with race etc, Mendelian inheritance COULD work like it does on Roshar. They just have to be genetically different enough from our humans, which I think they probably are.

There are several diseases in real life in which people have hair of mostly one colour but a forelock of another (e.g Waardenburg syndrome) and heterochromia iridium is not that rare either. It wouldn't take that much in terms of genetic difference on a planet in which the genetics are likely meddled with by the Shards (as we have also seen on Scadrial) to produce the multicoloured hair

The humans are not a visiting species, I think, as someone suggested above, but a native species formed in tribute to original humans by the Shards, but not the same, necessarily, as original humans or even Scadrians (who we know were created) and certainly no need to be the same as actual RL humans.

And when in doubt, sDNA can account for all kinds of oddities in the hereditary process

Edited April 16, 2016 by IndigoAjah

[Zea mays]

Corn.  Barbara McClintock, transposons, and corn

 

 

Well, either that or mosaicism.

Wow. Corn is Rosharan. I knew it.

[Mason Wheeler]

Corn.  Barbara McClintock, transposons, and corn

 

 

Well, either that or mosaicism.

 

Wow, that's interesting stuff!

[ecohansen]

Wow. Corn is Rosharan. I knew it.

Yep, Zea, your post maize me chuckle.

[Sunbird she/her]

Wow. Corn is Rosharan. I knew it.

 

Heh. I once read a book where the author asserted that broccoli was an alien plant and that's why so many people hate it. XD