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The sparrow with four sexes (2016)

nature.com

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Re: The sparrow with four sexes (2016)

#21

Post by nullc »

jojobas wrote: post #19
norrius wrote: post #17

Can someone explain what prevents birds of the same subtype from mating? The article mentions that the chromosome 2 cannot cross over in meiosis, but I just fail to understand the mechanics of the process and how that leads to disassortativity.

Having 2 copies of the mutated gene is probably deadly. They are saying an individual can only mate with a quarter of the population, but it's obviously incorrect, as the pre-mutation birds can mate with both mutated and unmutated opposite sex. The reason cross-morph pairs are observed more often as the mutated birds are more sexually aggressive and quickly round up unmutated opposite sex.

The article seemed to suggest that non-cross pairs are not observed at all, but they needed more genetic testing to determine if tan/tan never happens.

Even if the tan/tan is still physiologically possible it may be the case that they still won't mate even if there are no white present at all due to required mating signals being missing.

Re: The sparrow with four sexes (2016)

#22

Post by jojobas »

nullc wrote: post #21
jojobas wrote: post #19

Earlier quoted context omitted.

Having 2 copies of the mutated gene is probably deadly. They are saying an individual can only mate with a quarter of the population, but it's obviously incorrect, as the pre-mutation birds can mate with both mutated and unmutated opposite sex. The reason cross-morph pairs are observed more often as the mutated birds are more sexually aggressive and quickly round up unmutated opposite sex.

The article seemed to suggest that non-cross pairs are not observed at all, but they needed more genetic testing to determine if tan/tan never happens. Even if the tan/tan is still physiologically possible it may be the case that they still won't mate even if there are no white present at all due to required mating signals being missing.

From a different article:

So are females most strongly attracted to the tough, macho, white-striped males? Actually, no. Lab studies have found that females of either morph prefer the tan-striped males. White-striped females, more pushy than their tan-striped sisters, grab the tan-striped bachelors right away, so these pairs form more quickly than the opposite combination. Males of both morphs tend to prefer the white-striped females, but those females quickly hook up with tan-striped males if they can, so eventually the leftover birds will form pairs consisting of white-striped males and tan-striped females.

https://www.audubon.org/news/the-fascinating-and-complicated...

Granted, the question of homo-zygotic white offspring viability is not even touched.

Edit: yet another article tentatively says the double-white sparrows to exist, but in far lesser number than expected, they suspect some genetic disadvantage.

https://www.cell.com/current-biology/fulltext/S0960-9822(15)...

Re: The sparrow with four sexes (2016)

#23

Post by b0rsuk »

It's a common idea that evolution propagates useful mutations, and the non-useful disappear. How does it help a bird to have four sexes?

Or maybe it's just irrelevant for birds. Birds appear to break many laws of nature other animals have to abide by. They fly, they move where they want. They stay close to humans, observe them, and easily avoid them. They're amazingly energetic for how big they are. They migrate extremely far. They don't have to commit to anything except when rearing young.

Re: The sparrow with four sexes (2016)

#24

Post by jwilk »

geofft wrote: post #5
loa_in_ wrote: post #2

It sounds like they're evolving into separate species. Indeed it's one definition of a species that it's a population that can mate within it's group. So if they can no longer breed with each other, are they same species or not?

If I'm reading right, the two groups can only breed with each other. That is, white-striped males and tan-striped females can breed, as can white-striped females and tan-striped males. (And the offspring are about half white-striped and half tan-striped.) So it's not speciation, any more than sexes themselves are speciation.

> white-striped males and tan-striped females can breed, as can white-striped females and tan-striped males

This alone doesn't contradict the two-species theory. It could be that white-M + tan-F is species #1, and white-F + tan-M is species #2. Sure, it sounds weird, but not nearly as weird as the idea of 4 sexes, IMO.

> (And the offspring are about half white-striped and half tan-striped.)

Now, this is the important part. As I understand it, the offspring of "species #1" could be "species #2" or the other way round. This indicates that #1 and #2 are the same species after all.

Re: The sparrow with four sexes (2016)

#26

Post by msla »

b0rsuk wrote: post #23

It's a common idea that evolution propagates useful mutations, and the non-useful disappear. How does it help a bird to have four sexes? Or maybe it's just irrelevant for birds. Birds appear to break many laws of nature other animals have to abide by. They fly, they move where they want. They stay close to humans, observe them, and easily avoid them. They're amazingly energetic for how big they are. They migrate extr…

> It's a common idea that evolution propagates useful mutations, and the non-useful disappear.

Common ideas are commonly wrong. Non-useful ones only disappear reliably if they're selected against. Otherwise, you get goose bumps, or piloerection in humans: We don't have enough hair over most of our bodies for erecting it to do any good, but we still have all the structures to erect it anyway, because none of our ancestors lost any of them even as they became useless.

Re: The sparrow with four sexes (2016)

#27

Post by mjburgess »

msla wrote: post #26
b0rsuk wrote: post #23

It's a common idea that evolution propagates useful mutations, and the non-useful disappear. How does it help a bird to have four sexes? Or maybe it's just irrelevant for birds. Birds appear to break many laws of nature other animals have to abide by. They fly, they move where they want. They stay close to humans, observe them, and easily avoid them. They're amazingly energetic for how big they are. They migrate extr…

> It's a common idea that evolution propagates useful mutations, and the non-useful disappear. Common ideas are commonly wrong. Non-useful ones only disappear reliably if they're selected against. Otherwise, you get goose bumps, or piloerection in humans: We don't have enough hair over most of our bodies for erecting it to do any good, but we still have all the structures to erect it anyway, because none of our ances…

"Useful" is also context-dependent in two ways: it is relative to the environment of adaption; and also! relative to the existing genotype.

ie., evolution is starting with a bike and turning it into a car

it is not "starting with raw materials" and shaping them

So pretty much every life form is highly non-optimal wrt their environments.

Re: The sparrow with four sexes (2016)

#28

Post by msla »

mjburgess wrote: post #27
msla wrote: post #26

Earlier quoted context omitted.

> It's a common idea that evolution propagates useful mutations, and the non-useful disappear. Common ideas are commonly wrong. Non-useful ones only disappear reliably if they're selected against. Otherwise, you get goose bumps, or piloerection in humans: We don't have enough hair over most of our bodies for erecting it to do any good, but we still have all the structures to erect it anyway, because none of our ances…

"Useful" is also context-dependent in two ways: it is relative to the environment of adaption; and also! relative to the existing genotype. ie., evolution is starting with a bike and turning it into a car it is not "starting with raw materials" and shaping them So pretty much every life form is highly non-optimal wrt their environments.

My point is that, as an optimizer, evolution is a very simplistic one. People try to explain why it does or doesn't do things, often falling into "just-so stories" as a result, and fail to grasp just how inhuman the process is.

Also:

> ie., evolution is starting with a bike and turning it into a car

> it is not "starting with raw materials" and shaping them

I'm not sure if you're drawing a distinction between evolution and abiogenesis here. You're right, in that technically evolution doesn't come into play until you have self-replicators of some form, but in colloquial terminology "evolution" is used to encompass the entire process all the way back to whatever nonliving organic chemicals formed the basis for the first life.

Re: The sparrow with four sexes (2016)

#29

Post by TeMPOraL »

msla wrote: post #28
mjburgess wrote: post #27

Earlier quoted context omitted.

"Useful" is also context-dependent in two ways: it is relative to the environment of adaption; and also! relative to the existing genotype. ie., evolution is starting with a bike and turning it into a car it is not "starting with raw materials" and shaping them So pretty much every life form is highly non-optimal wrt their environments.

My point is that, as an optimizer, evolution is a very simplistic one. People try to explain why it does or doesn't do things, often falling into "just-so stories" as a result, and fail to grasp just how inhuman the process is. Also: > ie., evolution is starting with a bike and turning it into a car > it is not "starting with raw materials" and shaping them I'm not sure if you're drawing a distinction between evoluti…

I understood them to mean that evolution evolves things on an ongoing basis, and doesn't start from abiogenesis each time. So the current form of a bird species is very much constrained by the form of what it evolved from.

I'd also add that it seems evolution isn't even turning bicycles to cars bolt by bolt, but is adding whole subsystems at a time. It's as if each bike was made of a set of standard ACME parts, and came with a set of blueprints for many other kinds of ACME parts - and evolution, at the large animal level, is just replacing one standardized part for another, or adding new ones where they didn't exist, or altering the manufacturing timings, etc.

I'm of course referring to the findings of evolutionary developmental biology - https://en.wikipedia.org/wiki/Evolutionary_developmental_bio....

Re: The sparrow with four sexes (2016)

#30

Post by ralfd »

bregma wrote: post #7
loa_in_ wrote: post #2

It sounds like they're evolving into separate species. Indeed it's one definition of a species that it's a population that can mate within it's group. So if they can no longer breed with each other, are they same species or not?

Just wait until you learn about the sex life of hexaploid species... an offspring needs parents of at least 3 different sexes.

What species ist that?
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