Scrutable

Turns out that life really does find a way in dinosaurs birds.

https://amp.theatlantic.com/amp/article/620517/

The article mentions that turkeys can also do virgin birth, which explains why we eat them at Christmas.

We eat Turkeys at Thanksgiving.

Alas COVID rules restrict us to a maximum of 20 people this year, which is 17 more than we were allowed last year.

Chris Preston wrote: Fri Oct 29, 2021 2:09 am We eat Turkeys at Thanksgiving.

Alas COVID rules restrict us to a maximum of 20 people this year, which is 17 more than we were allowed last year.

Well that's certainly more than I could eat.

dyqik wrote: Fri Oct 29, 2021 12:05 am The article mentions that turkeys can also do virgin birth, which explains why we eat them at Christmas.

"Because of birds’ chromosome system—ZZ makes males and ZW makes females—all avian parthenotes are males."
In humans XX makes females and XY males. If the virgin birth of Jesus really happened that would imply that Jesus was a woman.

jaap wrote: Fri Oct 29, 2021 9:21 am

dyqik wrote: Fri Oct 29, 2021 12:05 am The article mentions that turkeys can also do virgin birth, which explains why we eat them at Christmas.

"Because of birds’ chromosome system—ZZ makes males and ZW makes females—all avian parthenotes are males."
In humans XX makes females and XY males. If the virgin birth of Jesus really happened that would imply that Jesus was a woman.

This sounds like a spectacular car crash of a conversation to have with one of those evangelicals who tried to build scientific explanations for how god could carry out miracles.

jaap wrote: Fri Oct 29, 2021 9:21 am

dyqik wrote: Fri Oct 29, 2021 12:05 am The article mentions that turkeys can also do virgin birth, which explains why we eat them at Christmas.

"Because of birds’ chromosome system—ZZ makes males and ZW makes females—all avian parthenotes are males."
In humans XX makes females and XY males. If the virgin birth of Jesus really happened that would imply that Jesus was a woman.

Though, that can be seen as a very reductionist attitude.

If jesus had of been a woman with an xx, i would't have of transcended any natural laws,it would be what yu would expect and therefore not a miracle. That jesus was not a woman transcends natural law and is, ergo, a miracle.
IANA person who knows anything about this

dyqik wrote: Thu Oct 28, 2021 10:39 pm Turns out that life really does find a way in dinosaurs birds.

https://amp.theatlantic.com/amp/article/620517/

I'd missed this! Very cool indeed - and a good writeup from the Atlantic too.

I wonder about the conservation implications. Numbers of females are generally the limiting factor in populations (because males can impregnate multiple females - though this is less of a factor in birds where both parents incubate the egg, which is the case with California Condors). It's probably better than nothing, even if it's not increasing what we call "effective population size" nor genetic diversity, because with such a small population stochastic mortality (illness, misadventure, etc.) could be a sizeable determinant of population size, so the more the merrier.

I also didn't know that some poultry breeds have high rates of parthenogenesis. It's interesting that rates can vary so much within species, which to my mind suggests it might be a fairly labile trait in evolutionary terms. Seems like it might be a useful last-resort for slow-reproducing species (which poultry aren't - loads of offspring with high mortality). I expect there's not that much data on its frequency across species, because getting genomes of parents and offspring in wild populations is generally quite labour-intensive.

Exciting stuff. I hope it sparks some more work from wildlife geneticist types.

Bird on a Fire wrote: Fri Oct 29, 2021 2:58 pm

dyqik wrote: Thu Oct 28, 2021 10:39 pm Turns out that life really does find a way in dinosaurs birds.

https://amp.theatlantic.com/amp/article/620517/

I'd missed this! Very cool indeed - and a good writeup from the Atlantic too.

I wonder about the conservation implications. Numbers of females are generally the limiting factor in populations (because males can impregnate multiple females - though this is less of a factor in birds where both parents incubate the egg, which is the case with California Condors). It's probably better than nothing, even if it's not increasing what we call "effective population size" nor genetic diversity, because with such a small population stochastic mortality (illness, misadventure, etc.) could be a sizeable determinant of population size, so the more the merrier.

With the parthenotes all being male, it doesn't exactly help with the number of females limiting the population.

I guess what it does for genetic diversity is to provide an additional path for one female's genes to mix with another female's genes within two generations, contributing a different mix of genes to the regular offspring of that same female - where the regular offspring's genes are a mixture of the two parents, the parthenote's genes are a pure copy of the mother's genes. I think the effect on population diversity would be much the same as if the mother could breed directly with another female.

Yes, I guess you could think of it as a way for the female to spread her genes over a second generation.

It's just that with a tiny population, and six years to sexual maturity, time is very much of the essence.

Gfamily wrote: Fri Oct 29, 2021 1:02 pm

jaap wrote: Fri Oct 29, 2021 9:21 am

dyqik wrote: Fri Oct 29, 2021 12:05 am The article mentions that turkeys can also do virgin birth, which explains why we eat them at Christmas.

"Because of birds’ chromosome system—ZZ makes males and ZW makes females—all avian parthenotes are males."
In humans XX makes females and XY males. If the virgin birth of Jesus really happened that would imply that Jesus was a woman.

Though, that can be seen as a very reductionist attitude.

The Y chromosome is just a degenerate X, so it could be a miracle.

Bird on a Fire wrote: Fri Oct 29, 2021 3:17 pm Yes, I guess you could think of it as a way for the female to spread her genes over a second generation.

It's just that with a tiny population, and six years to sexual maturity, time is very much of the essence.

Yes, it'd definitely be helpful in a very small population.

jaap wrote: Fri Oct 29, 2021 9:21 am

dyqik wrote: Fri Oct 29, 2021 12:05 am The article mentions that turkeys can also do virgin birth, which explains why we eat them at Christmas.

"Because of birds’ chromosome system—ZZ makes males and ZW makes females—all avian parthenotes are males."
In humans XX makes females and XY males. If the virgin birth of Jesus really happened that would imply that Jesus was a woman.

Yup - I remember Dad telling me that when I was a kid.

Is there any idea how the mammalian sex chromosome system evolved?


I assume the XY version is newer than the WZ system if snakes, crocodilians and birds at least have that version. And at least some crocodile eggs can have their sex determined by the incubating conditions (I think temperature).

jimbob wrote: Fri Oct 29, 2021 9:34 pm Is there any idea how the mammalian sex chromosome system evolved?


I assume the XY version is newer than the WZ system if snakes, crocodilians and birds at least have that version. And at least some crocodile eggs can have their sex determined by the incubating conditions (I think temperature).

Late night cba-to-check answer, but i think the issue of "generic sex determination" more generally is a bit complex. Which sex is the heterozygotic one has switched multiple times, with the determining chromosome changing, but it can also happen during development (eg some fish) or due to environmental factors (eg many turtles' sex is temperature dependent, which is why all the dumped turtles from the 90s didn't take over the UK).

There was a good piece on Thr Skeptic a couple of months ago covering at least some of these points, but better. I can dig out links etc tomorrow if someone @s me.

jimbob wrote: Fri Oct 29, 2021 9:34 pm Is there any idea how the mammalian sex chromosome system evolved?


I assume the XY version is newer than the WZ system if snakes, crocodilians and birds at least have that version. And at least some crocodile eggs can have their sex determined by the incubating conditions (I think temperature).

It's possible that this was a response to (a) internalisation of eggs and (b) homeothermy. Naturally, a temperature dependent sex mechanism doesn't work too well if eggs are internal and at constant temperature! Since genetic mechanisms are often silenced rather than removed during evolution (see atavisms like teeth being induced from avian tissue, whales re-expressing parts of hind limbs and human babies being born with tails), it's possible that mammals still have the 'temperature dependent pathway' but it has been co-opted to be activated by SRY (since evolution often adapts existing pathways rather than inventing new ones from scratch).


http://aerg.canberra.edu.au/library/sex ... humans.pdf