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https://indiandefencereview.com/its-official-dolphins-and-orcas-have- now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to- land-again/
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinarCOs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsrCosuch as specialized
limbs, unique diets, and reproductive systemsrCohave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
https://indiandefencereview.com/its-official-dolphins-and-orcas-have-now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to-land-again/While a strict understanding of Dollo is almost certainly true, there
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinarCOs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsrCosuch as specialized
limbs, unique diets, and reproductive systemsrCohave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
On 7/6/2025 10:09 PM, Pro Plyd wrote:
Never say never.-a How did fish adapt to terrestrial life styles?
https://indiandefencereview.com/its-official-dolphins-and-orcas-have-
now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to-
land-again/
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinarCOs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsrCosuch as specialized
limbs, unique diets, and reproductive systemsrCohave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
Dolphins already have lungs.
On 7/6/2025 10:09 PM, Pro Plyd wrote:
Never say never. How did fish adapt to terrestrial life styles?
https://indiandefencereview.com/its-official-dolphins-and-orcas-have-
now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to-
land-again/
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinaAs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsusuch as specialized
limbs, unique diets, and reproductive systemsuhave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
Dolphins already have lungs.
On Mon, 7 Jul 2025 07:01:51 -0500, the following appeared inIt's a matter of probability. Between random genetic events and
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/6/2025 10:09 PM, Pro Plyd wrote:The whole thing sounds to me like "We can't imagine how this
Never say never. How did fish adapt to terrestrial life styles?
https://indiandefencereview.com/its-official-dolphins-and-orcas-have-
now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to-
land-again/
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinarCOs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsrCosuch as specialized
limbs, unique diets, and reproductive systemsrCohave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
Dolphins already have lungs.
could be accomplished, so it can't; simply too many
simultaneous changes are required", an assertion more
familiar from evolution denialists than from (supposed)
scientists. I wonder if they think that cetaceans became
semiaquatic (not fully; they still can't breathe underwater)
in one fell swoop? And if not, why the same gradual process
won't work in reverse?
On Mon, 07 Jul 2025 08:00:09 -0700, Bob Casanova <nospam@buzz.off>
wrote:
On Mon, 7 Jul 2025 07:01:51 -0500, the following appeared in
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/6/2025 10:09 PM, Pro Plyd wrote:The whole thing sounds to me like "We can't imagine how this
Never say never. How did fish adapt to terrestrial life styles?
https://indiandefencereview.com/its-official-dolphins-and-orcas-have-
now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to- >>>> land-again/
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinarCOs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsrCosuch as specialized
limbs, unique diets, and reproductive systemsrCohave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
Dolphins already have lungs.
could be accomplished, so it can't; simply too many
simultaneous changes are required", an assertion more
familiar from evolution denialists than from (supposed)
scientists. I wonder if they think that cetaceans became
semiaquatic (not fully; they still can't breathe underwater)
in one fell swoop? And if not, why the same gradual process
won't work in reverse?
It's a matter of probability. Between random genetic events and
random environmental events, it's almost impossible for any *exact* evolutionary pathway to be repeated. It would be like a broken glass reassembling itself.
On 7/8/2025 4:36 AM, jillery wrote:
On Mon, 07 Jul 2025 08:00:09 -0700, Bob Casanova <nospam@buzz.off>
wrote:
On Mon, 7 Jul 2025 07:01:51 -0500, the following appeared in
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/6/2025 10:09 PM, Pro Plyd wrote:The whole thing sounds to me like "We can't imagine how this
Never say never. How did fish adapt to terrestrial life styles?
https://indiandefencereview.com/its-official-dolphins-and-orcas-have- >>>>> now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to- >>>>> land-again/
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinaAs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsusuch as specialized
limbs, unique diets, and reproductive systemsuhave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
Dolphins already have lungs.
could be accomplished, so it can't; simply too many
simultaneous changes are required", an assertion more
familiar from evolution denialists than from (supposed)
scientists. I wonder if they think that cetaceans became
semiaquatic (not fully; they still can't breathe underwater)
in one fell swoop? And if not, why the same gradual process
won't work in reverse?
It's a matter of probability. Between random genetic events and
random environmental events, it's almost impossible for any *exact*
evolutionary pathway to be repeated. It would be like a broken glass
reassembling itself.
What is stupid about the claim is that they do not acknowledge the >possiblity of a new path to terrestrial adaptation. There is no reason
to limit how they might adapt to life on land. They have a new starting >point and have broken a lot of bridges to get to where they are, but
there are likely multiple paths back to living on land, especially, just >back to an amphibian type life style.
On Tue, 8 Jul 2025 07:22:01 -0500, the following appeared in
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/8/2025 4:36 AM, jillery wrote:
On Mon, 07 Jul 2025 08:00:09 -0700, Bob Casanova <nospam@buzz.off>
wrote:
On Mon, 7 Jul 2025 07:01:51 -0500, the following appeared in
That was pretty much my thought; while an exact "replay inIt's a matter of probability. Between random genetic events and
random environmental events, it's almost impossible for any *exact*
evolutionary pathway to be repeated. It would be like a broken glass
reassembling itself.
What is stupid about the claim is that they do not acknowledge the >>possiblity of a new path to terrestrial adaptation. There is no reason
to limit how they might adapt to life on land. They have a new starting >>point and have broken a lot of bridges to get to where they are, but
there are likely multiple paths back to living on land, especially, just >>back to an amphibian type life style.
reverse" would be essentially impossible, as you say there
are multiple paths. All that would be required would be a
re-creation of function, not an exact "reboot".
As has been pointed out several times, a re-start at the
original point would almost certainly (probability as close
to zero as can be imagined) *not* follow the identical path
resulting in the current species, but the same challenges
should result in something similar.
On Tue, 8 Jul 2025 07:22:01 -0500, the following appeared inIt depends on which claim you mean. A new path would not be a
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/8/2025 4:36 AM, jillery wrote:
On Mon, 07 Jul 2025 08:00:09 -0700, Bob Casanova <nospam@buzz.off>
wrote:
On Mon, 7 Jul 2025 07:01:51 -0500, the following appeared in
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/6/2025 10:09 PM, Pro Plyd wrote:The whole thing sounds to me like "We can't imagine how this
Never say never. How did fish adapt to terrestrial life styles?
https://indiandefencereview.com/its-official-dolphins-and-orcas-have- >>>>>> now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to- >>>>>> land-again/
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinarCOs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsrCosuch as specialized
limbs, unique diets, and reproductive systemsrCohave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
Dolphins already have lungs.
could be accomplished, so it can't; simply too many
simultaneous changes are required", an assertion more
familiar from evolution denialists than from (supposed)
scientists. I wonder if they think that cetaceans became
semiaquatic (not fully; they still can't breathe underwater)
in one fell swoop? And if not, why the same gradual process
won't work in reverse?
It's a matter of probability. Between random genetic events and
random environmental events, it's almost impossible for any *exact*
evolutionary pathway to be repeated. It would be like a broken glass
reassembling itself.
What is stupid about the claim is that they do not acknowledge the >>possiblity of a new path to terrestrial adaptation. There is no reason
to limit how they might adapt to life on land. They have a new starting >>point and have broken a lot of bridges to get to where they are, but
there are likely multiple paths back to living on land, especially, just >>back to an amphibian type life style.
That was pretty much my thought; while an exact "replay inBy analogy, it's possible flightless birds could potentially re-evolve functional flight, but the newly evolved structures would necessarily
reverse" would be essentially impossible, as you say there
are multiple paths. All that would be required would be a
re-creation of function, not an exact "reboot".
As has been pointed out several times, a re-start at the
original point would almost certainly (probability as close
to zero as can be imagined) *not* follow the identical path
resulting in the current species, but the same challenges
should result in something similar.
On Tue, 08 Jul 2025 15:03:35 -0700, Bob Casanova <nospam@buzz.off>
wrote:
On Tue, 8 Jul 2025 07:22:01 -0500, the following appeared in
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/8/2025 4:36 AM, jillery wrote:
On Mon, 07 Jul 2025 08:00:09 -0700, Bob Casanova <nospam@buzz.off>
wrote:
On Mon, 7 Jul 2025 07:01:51 -0500, the following appeared in
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/6/2025 10:09 PM, Pro Plyd wrote:The whole thing sounds to me like "We can't imagine how this
Never say never. How did fish adapt to terrestrial life styles?
https://indiandefencereview.com/its-official-dolphins-and-orcas-have- >>>>>>> now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to- >>>>>>> land-again/
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinarCOs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsrCosuch as specialized
limbs, unique diets, and reproductive systemsrCohave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
Dolphins already have lungs.
could be accomplished, so it can't; simply too many
simultaneous changes are required", an assertion more
familiar from evolution denialists than from (supposed)
scientists. I wonder if they think that cetaceans became
semiaquatic (not fully; they still can't breathe underwater)
in one fell swoop? And if not, why the same gradual process
won't work in reverse?
It's a matter of probability. Between random genetic events and
random environmental events, it's almost impossible for any *exact*
evolutionary pathway to be repeated. It would be like a broken glass
reassembling itself.
What is stupid about the claim is that they do not acknowledge the
possiblity of a new path to terrestrial adaptation. There is no reason
to limit how they might adapt to life on land. They have a new starting >>> point and have broken a lot of bridges to get to where they are, but
there are likely multiple paths back to living on land, especially, just >>> back to an amphibian type life style.
It depends on which claim you mean. A new path would not be a
violation of Dollo's Law:
<https://en.wikipedia.org/wiki/Dollo%27s_law_of_irreversibility>
As I pointed out, it is practically impossible for aquatic mammals to
reverse the traits which make them aquatic and restore their ancestral
land forms. However, as I also pointed out elsepost, tortoises became secondarily land animals from ancestral aquatic forms. So the claim
that aquatic mammals could not evolve back to a completely different terrestrial form is also incorrect. Just as with tortoises, these
newly evolved terrestrial forms would necessarily retain traits of
their aquatic past. That's the point of Dollo's Law.
That was pretty much my thought; while an exact "replay in
reverse" would be essentially impossible, as you say there
are multiple paths. All that would be required would be a
re-creation of function, not an exact "reboot".
As has been pointed out several times, a re-start at the
original point would almost certainly (probability as close
to zero as can be imagined) *not* follow the identical path
resulting in the current species, but the same challenges
should result in something similar.
By analogy, it's possible flightless birds could potentially re-evolve functional flight, but the newly evolved structures would necessarily
be very different from those of extant flying birds.
On 7/9/2025 3:25 AM, jillery wrote:
On Tue, 08 Jul 2025 15:03:35 -0700, Bob Casanova <nospam@buzz.off>
wrote:
On Tue, 8 Jul 2025 07:22:01 -0500, the following appeared in
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/8/2025 4:36 AM, jillery wrote:
On Mon, 07 Jul 2025 08:00:09 -0700, Bob Casanova <nospam@buzz.off>
wrote:
On Mon, 7 Jul 2025 07:01:51 -0500, the following appeared in
talk.origins, posted by RonO <rokimoto557@gmail.com>:
On 7/6/2025 10:09 PM, Pro Plyd wrote:The whole thing sounds to me like "We can't imagine how this
Never say never.-a How did fish adapt to terrestrial life styles? >>>>>>> Dolphins already have lungs.
https://indiandefencereview.com/its-official-dolphins-and-orcas-have- >>>>>>>> now-crossed-the-point-of-no-return-in-their-evolution-of-returning-to- >>>>>>>> land-again/
Dolphins and orcas, revered for their intelligence
and agility, have reached a pivotal point in their
evolutionary journey. New research has revealed
that these marine mammals, once land-dwellers, have
evolved to a stage where returning to life on land
is biologically impossible. A breakthrough study
underscores that after millions of years of
evolutionary change, dolphins and orcas are now
forever bound to the ocean.
Published in Proceedings of the Royal Society B,
the study scrutinized over 5,600 mammal species
to understand how dolphins and orcas evolved from
semi-aquatic ancestors to fully marine life forms.
The research, led by Bruna Farina, a PhD candidate
at the University of Fribourg in Switzerland,
concludes that the transition from semi-aquatic to
fully aquatic is a one-way path. Once a species
makes this leap, its evolutionary direction becomes
irreversible.
FarinarCOs team found that this transition occurred
millions of years ago when mammals returned to the
sea. Unlike their terrestrial predecessors, dolphins
and orcas cannot evolve back to a land-based
lifestyle. Their adaptationsrCosuch as specialized
limbs, unique diets, and reproductive systemsrCohave
become so ingrained that reversing these traits is
no longer possible.
...
The paper is here
https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1099
Dollo meets Bergmann: morphological evolution in
secondary aquatic mammals
could be accomplished, so it can't; simply too many
simultaneous changes are required", an assertion more
familiar from evolution denialists than from (supposed)
scientists. I wonder if they think that cetaceans became
semiaquatic (not fully; they still can't breathe underwater)
in one fell swoop? And if not, why the same gradual process
won't work in reverse?
It's a matter of probability.-a Between random genetic events and
random environmental events, it's almost impossible for any *exact*
evolutionary pathway to be repeated.-a It would be like a broken glass >>>>> reassembling itself.
What is stupid about the claim is that they do not acknowledge the
possiblity of a new path to terrestrial adaptation.-a There is no reason >>>> to limit how they might adapt to life on land.-a They have a new
starting
point and have broken a lot of bridges to get to where they are, but
there are likely multiple paths back to living on land, especially,
just
back to an amphibian type life style.
It depends on which claim you mean.-a A new path would not be a
violation of Dollo's Law:
<https://en.wikipedia.org/wiki/Dollo%27s_law_of_irreversibility>
As I pointed out, it is practically impossible for aquatic mammals to
reverse the traits which make them aquatic and restore their ancestral
land forms.-a However, as I also pointed out elsepost, tortoises became
secondarily land animals from ancestral aquatic forms.-a So the claim
that aquatic mammals could not evolve back to a completely different
terrestrial form is also incorrect.-a Just as with tortoises, these
newly evolved terrestrial forms would necessarily retain traits of
their aquatic past.-a That's the point of Dollo's Law.
My take is that they would not have to take the reverse path.-a It is
much more likely that they would evolve into a seal like terrestrial
animal if we drove pinnipeds to extinction and left that niche open.
They would not go back to a lunging croc like animal like ambulocetus. Further terrestrial evolution would depend on what niche was open that
they could exploit.
That was pretty much my thought; while an exact "replay in
reverse" would be essentially impossible, as you say there
are multiple paths. All that would be required would be a
re-creation of function, not an exact "reboot".
As has been pointed out several times, a re-start at the
original point would almost certainly (probability as close
to zero as can be imagined) *not* follow the identical path
resulting in the current species, but the same challenges
should result in something similar.
By analogy, it's possible flightless birds could potentially re-evolve
functional flight, but the newly evolved structures would necessarily
be very different from those of extant flying birds.
flightless birds still have feathers, but they are more like the
feathers dinos had in some cases.-a In a lot of cases the wing feathers
do not develop properly and are too short or the bird is now too heavy
to fly.-a You would not have to reevolve flight feathers, just redevelop flight functional feathers, and you would not have to do it by
recreating what got broken, you could do it by taking a path similar to
the one taken by dinos to evolve the flight capable feathers in the
first place, but you already have flight feathers.-a My take is that if
the flighted birds went extinct that even ratites could reevolve flight using feathers, but they would have to reevolve the feather structure
needed for flight.-a They still have the basic capability, they just need
to improve it like dinos did.-a They would not have to do it in exactly
the same way that dinos did it.-a They all still have keels, as far as I know, so they would not have to reevolve that structure for flight
muscle attachment.
Ron Okimoto