https://www.iflscience.com/snail-that-gives-birth-to-live-young-reveals-evolutionary-leaps-happen-gradually-72291

Egg laying was the go-to for snails for millions
of years – but at some point in the last 100,000,
a group of marine snails ditched eggs in favor of
live birth. The switch happened in the blink of an
eye in evolutionary terms, and scientists have now
discovered that it was driven by around 50 genetic
changes. The rare opportunity to study the genetic
architecture of an evolutionary change has revealed
that the secret isn’t making one huge leap, it's
about the accumulation of many gradual changes.
....
Tracing back through the wealth of genetic
information revealed that live-bearing young in
marine snails emerged gradually over the last
100,000 years as a series of mutations accumulated.
However, we don't yet know which of those
incremental changes were pivotal in the striking
change in reproductive strategy.

"Exactly which one was needed specifically for the
live-bearing trait, I think we can’t say at the
moment,” continued Butlin. “All of the 50 occur
together in all the live-bearing snails, so it looks
like many of them are necessary – together – for
live-bearing. But some of them, we think, are
probably responsible for other things that go with
live-bearing, like the change to breeding
all-year-round instead of breeding only in one
season.”
....

https://www.science.org/doi/10.1126/science.adm9239
Evolutionary paths to new phenotypes
Ecological model systems inform on innovative traits
in plants and animals

Abstract
Adaptation by natural selection cannot take any
evolutionary path; it operates within the
constraints of genetic variation and environmental
context, with futures contingent on the past.
Therefore, how new suites of traits arise is an
enduring issue and is key to understanding the
diversity of life (1). On pages 108 and 114 of
this issue, Chomicki et al. (2) and Stankowski
et al. (3), respectively, investigate two
different cases of fascinating biological
complexity that arose through convergent and
convoluted evolutionary paths—one in carnivorous
pitcher plants (Nepenthes gracilis and Nepenthes
pervillei) and another in marine periwinkle snails
(Littorina saxatilis). The studies use different
approaches to reconstruct evolution to reveal how
complex phenotypic traits arise in unexpected ways.
The results advance understanding not only of the
specific traits that are studied—feeding structures
in plants and live-bearing (as opposed to
egg-laying) in snails—but also how evolution in
general might arrive at apparently unlikely
combinations.

To complicate this, do we say that a fertilised
egg is a living thing? I'm not making a point
about evolution exactly, just looking for an
argument. :-) Or perhaps to say that a critter
that leaves its parent* inside an eggshell
and one that comes out naked aren't so much
different. *Sea horses. And "George Francisco"
in _Alien Nation_ (TV).

On 1/14/24 3:30 AM, Robert Carnegie wrote:
> To complicate this, do we say that a fertilised
> egg is a living thing? I'm not making a point
> about evolution exactly, just looking for an
> argument. :-) Or perhaps to say that a critter
> that leaves its parent* inside an eggshell
> and one that comes out naked aren't so much
> different. *Sea horses. And "George Francisco"
> in _Alien Nation_ (TV).
>
There are upsides and downsides to everything.

On 1/5/2024 9:15 PM, Pro Plyd wrote:
>
>
> https://www.iflscience.com/snail-that-gives-birth-to-live-young-reveals-evolutionary-leaps-happen-gradually-72291
>
> Egg laying was the go-to for snails for millions
> of years – but at some point in the last 100,000,
> a group of marine snails ditched eggs in favor of
> live birth. The switch happened in the blink of an
> eye in evolutionary terms, and scientists have now
> discovered that it was driven by around 50 genetic
> changes. The rare opportunity to study the genetic
> architecture of an evolutionary change has revealed
> that the secret isn’t making one huge leap, it's
> about the accumulation of many gradual changes.
> ...
> Tracing back through the wealth of genetic
> information revealed that live-bearing young in
> marine snails emerged gradually over the last
> 100,000 years as a series of mutations accumulated.
> However, we don't yet know which of those
> incremental changes were pivotal in the striking
> change in reproductive strategy.
>
> "Exactly which one was needed specifically for the
> live-bearing trait, I think we can’t say at the
> moment,” continued Butlin. “All of the 50 occur
> together in all the live-bearing snails, so it looks
> like many of them are necessary – together – for
> live-bearing. But some of them, we think, are
> probably responsible for other things that go with
> live-bearing, like the change to breeding
> all-year-round instead of breeding only in one
> season.”
> ...
>
>
> https://www.science.org/doi/10.1126/science.adm9239
> Evolutionary paths to new phenotypes
> Ecological model systems inform on innovative traits
> in plants and animals
>
>
> Abstract
> Adaptation by natural selection cannot take any
> evolutionary path; it operates within the
> constraints of genetic variation and environmental
> context, with futures contingent on the past.
> Therefore, how new suites of traits arise is an
> enduring issue and is key to understanding the
> diversity of life (1). On pages 108 and 114 of
> this issue, Chomicki et al. (2) and Stankowski
> et al. (3), respectively, investigate two
> different cases of fascinating biological
> complexity that arose through convergent and
> convoluted evolutionary paths—one in carnivorous
> pitcher plants (Nepenthes gracilis and Nepenthes
> pervillei) and another in marine periwinkle snails
> (Littorina saxatilis). The studies use different
> approaches to reconstruct evolution to reveal how
> complex phenotypic traits arise in unexpected ways.
> The results advance understanding not only of the
> specific traits that are studied—feeding structures
> in plants and live-bearing (as opposed to
> egg-laying) in snails—but also how evolution in
> general might arrive at apparently unlikely
> combinations.
>
>
>
>
The article is paywalled, but I subscribe.
https://pubmed.ncbi.nlm.nih.gov/38175895/

It isn't a normal example of evolution. Populations that were thought
to be the same species turned out to not be monophyletic. It looks like
after live bearing reproduction evolved in one lineage, two species
interbred and the live bearing genes were transferred to a different
lineage. Whole genome phylogenetic analysis places the two live bearing
species as different lineages, but one of the lineages has most of the
genome of one species, but has the reproductive genes from the other
live bearing species.

This is an example that Behe should be looking into. It looks like the
live bearing phenotype is associated with 50 recent variants that the
authors claim were "recruited" to evolve the live bearing phenotype.
They claim that it was likely that many variants had to come together to
create the live bearing form of reproduction. They haven't worked out
the order of when the mutations needed to occur, but they claim in the
paper that it is likely that several of the mutations likely had to
exist before the phenotype could evolve.

Behe wants his 3 neutral mutations within a given period of time to
evolve new function and make a system his type of IC. These researchers
claim that around 50 variants were "recruited" within the last 200,000
generations to produce the live-bearing phenotype. My guess is that
they use recruited instead of mutation because the variants could have
come from other species. They already have evidence that the whole
system could be transferred, so parts of it could have come from other
species.

Ron Okimoto