Many vertebrates have abandoned egg-laying for live birth. But despite some suggestive examples, convincing evidence for the evolutionary reversal of
this trait has been lacking until now.
Vincent Lynch and Günter Wagner at Yale University, New Haven, carried out a phylogenetic analysis of 41 species of boa snake using recent DNA data.
The most parsimonious explanation of the phylogeny, they conclude, is that the Arabian sand boa, Eryx jayakari (pictured ), one of only two species of
egg-laying boa, re-evolved this ability some 60 million years after the transition of the group to live birth.
E. jayakari also lacks the egg tooth other oviparous snakes use to tear their way out of the egg, additional evidence that egg-laying was lost and
reacquired, according to the authors.
Add a few 10's million years and they might even become rocket scientists...
ITs very interesting to think that animals could change they way they give birth. However i dont think in 100million years we would go to egg births.
I do believe that on some level we will evolve into another species of humanoids. Weither its with a higher consciousness or physcial ability.
Animals have been adapting to life and enviroment for ever and the one common link between all things is the atom. and i really believe all our
answers in life can be found by studing the atoms in our body and how the relate to our dna.
There's no possible way mammals will ever "evolve back into reptiles". It just doesn't work that way.
Firstly, in a sense, we never stopped being reptiles, because we are descended from a basal form of them. We cannot detach ourselves from our
ancestry. So we can still be seen as a type of highly adapted and specialized reptile. We're also still fish too.
"True Reptiles" as we classify them today split off when synapsids, diapsids, and anapsids all went their separate ways. We are synapsids, meaning
we have one hole bilaterally symmetrical to each other on either side of the skull. Reptiles are Diapsids, meaning they have two bilaterally
symmetrical holes on either side of their skull. (Anapsids have no holes, and IIRC - turtles are only remaining example of this line). However, they
all descend from a basal proto-reptile like Hylonomus.
As Synapsids (us) diverged further and further away, they become known as "mammal-like" reptiles which share traits basal to mammals and early
reptiles. An example of this would be Dimetradon. It still looks
rather reptilian to the casual observer. It's later descendants would start taking on more and more mammal like features. To which, a video of
Gorgonopsid from "Walking with Prehistoric Beasts" which gives a better impression of just how mammal-like these creatures were.
So even if mammals eventually took on features which we traditionally ascribe to reptiles - such as scales and slit eyes, they wouldn't be reptilian
eyes or scales. Merely mammalian features highly adapted and resembling the common public conceptualization of reptilian features. Some of these
already exist. Platypus and the Spiny Echidna both lay eggs. Felines have slitted eyes. The Pangolin
has scales for armor. Etc.
Remember that evolution ONLY moves forward. You cannot "De-Evolve". The closest to this would be the occasional activation of atavisms - like the
human tail. But these are rare and affect individuals only - not populations. Even still, it's moving forward. Even if a species looses a clearly
beneficial trait (it does happen occasionally), such as humanity's descendants losing our higher cognitive functions, it's still merely moving
forward to a different form.
(Though I'm not convinced that higher intelligence and cognition is a beneficial adaptation in the long run)
Oh, and speaking of the Platypus and Echidna - they didn't evolve to lay eggs once again. They are some of the last few remnants of monotremes, what
was the normal expression of Mammals, but has since been replaced by Eutherians (Placental Mammals). Metatheria (Marsupials) being the third
configuration at less than 300 species strong. They give birth to live young which are "larval" and finish their development outside of the
mother's body (often in a pouch or clung to specialized hairs by the nipple.
The term "De-Evolve" should not be used. Even if we look at it as moving backwards the late situation will always be an improved version.
Yes you're right, I think the more appropriate term is 'adaptation'.
I would imagine us humans right now, if our civ gets plunged back to stone age, we'll begin to loose that 'Paris Hilton' look and look more like
Klingons, but otherwise, a lot smarter, more mannered (less whiners) because now we have to manufacture our own stuff!
IMO The whole point of evolution is to adapt to your environment and to be able to adapt to climatic change... We used to be reptillians, which then
turned into mammals and in turn into us, what I am saying is that evoloution is going forward... it would be somewhat "a waste of time" for us to
de-evolve to become a reptillian.
Now, if you were to ask me is it possible for reptillians to evolve into a humanoid like creature my opinion would be somewhat different!
We do have species of animals that present the transient situation they've got trapped in. As an example look at the platypus.
As said, the Platypus (and to a degree, the Echidna) are the last remaining karyotypes of what used to be the norm of mammalian diversity. Monotremes
died off most everywhere else in the world, to be replaced by eutherians, but have survived in Australia - which isn't extremely surprising since
Australia is a fairly isolated continent.
It has venom like a snake
No, it has venom like a platypus. Rather than having the venom producing glands located in the skull or neck, the Platypus has them located on spurs
on their back legs. Now the venom itself is fairly similar to common snake venom, but this does not indicate a shared lineage in any fashion. Merely,
it represents what may become recognized as a common motif in biological evolution. For instance, in another thread asking about what qualifies as a
transitional fossil, I happened to give the example of mutations in South American Natives of the Andes and Indian natives of the Himalayan mountains
have similar but different mutations allowing for the increased sequestering of oxygen in high altitude environments. Two separate and unique
mutations, which gave the same basic effect, in two completely separate and isolated cultures.
Indeed, the platypus isn't even the only venomous mammal, and not all venomous mammals are monotremes.
Not at all. While the bill does resemble a duck's upon casual glance, they are not at all the same.
In fact, scientists have always known that the bill has nothing in common with that of a duck except for the shape. The bill of a duck is a hard
keratin structure, while that of the platypus is a soft flexible organ packed with electrical and touch sensors. While underwater, the bill is used to
explore the environment and find food. (Thus Huse also gets it wrong when he says the the platypus "uses echo location like dolphins"; it does
The comment "Remember that evolution ONLY moves forward. You cannot "De-Evolve" is completely wrong.
Not, it isn't. It's completely right. The phylogenetic tree does not have "go back" slides like Chutes and Ladders. We are all moving forward in a
continual line of descent with modification. If the environment selects certain morphological motifs, it's only because those motifs have continually
shown to be advantageous. For instance, Birds, Insects, and Mammals have all evolved specialized adaptations for flight. Some fish have also, to a
degree. This isn't indicative of their sharing a common ancestor they could revert back to in some way - but rather indicative that they share a
common environment. A planet with a substantial atmosphere.
whales (got back to the aquatic habitat)
Note the striking difference between the structure and placement of Whale fins when compared to those of fish. Notice, also, that whales still breathe
air from the surface rather than through gills.
Whales didn't de-evolve to an aquatic environment. They evolved from a terrestrial environment to an aquatic one.
snakes (they've lost limbs)
Simply loosing an adaptation is not indicative of "de-evolution". Humanity has lost their fur, but would you claim that we have de-evolved? Further,
the Glass Snake has lost it's legs - but it's not a snake, it's a legless lizard. We can tell by studying is physiognomy which biological clade it
belongs to. Again, Phylogeny is not a game of chutes of ladders. Evolution is more akin to a sculptor using currently existing traits and changing
those over time into something new. It does not revert back to previous models, even if the new adaptation bears resemblance to the old.
Don Exodus: The Constraints of Evolution.
penguins (their wings are turning into fins - like their reptilian ancestors)
No.... their wings are adapting to an aquatic environment. Reptiles didn't have "fins" for aquatic locomotion. Even some of the earliest amphibians
we know of had legs with rudimentary digits at the ends of their appendages. Well, the front ones anyhow. Reptiles came after amphibians.
To round this out a bit, perhaps an introduction to phylogenetics for the fellow members, by AronRa.
These are cases of evolutionary pressure giving origin to a new adaptation strategy in order to survive, not as the original species but as an
You've confirmed it yourself, in part. Thank you. There is no such thing as "de-evolution". There is only evolutionary pressure giving origin to
a new adaptation. Again, certain motifs are favored by the environment (Armadillos, Tortoises, and Ankylosaurus all have hard dorsal armor shells
for protection, but they are not inherited from one another)
Nature is not always right...
What is "right" is subjective. Nature isn't subjective, it just is.
actually, reason is not always correct because everything will change, it's only a matter of time.
Change doesn't affect the ability to reason. The ability to reason is affected by education, experience, and observation. Reason only stops being
effective if you stop learning and allow changes to compound upon each other. For instance, Thomas Paine was a deist in his day, and you can read many
papers of his which take you step by step through his reasoning of nature to come to his conclusion of god. Yet you cannot read those same works and
use his reasoning for your own basis of belief. (if you have one) This is because in his day it WAS reasonable to suspect design in the universe.
However, today with advanced astrophysics, genetics, evolution, paleontology, etc... most of his arguments have been nullified or explained by natural
evidence. As a champion of reason, Paine in today's world might learn of these new discoveries, and change his conclusion to a more faith-based Deism
- or Atheism.
We can't really say one way or another what he'd do, but I think the point is made just for example's sake.
Even if we look at it as moving backwards the late situation will always be an improved version.
Not necessarily. "Improved" is a subjective term, and can vary radically from environment to environment, adaptation to adaptation. In the above
example, Whales are the descendants of a forerunner who returned to an aquatic environment. However, no matter how impressive in capacity - the
whale's lungs are no competition for gills in terms of time spent below the surface.
It may be better suited for the current environment than an ancestral adaptation to a similar environment, but as the environment regardless would
have no doubt changed - neither adaptation is necessarily particularly well suited for the others environment. Emus are flightless birds, but their
wings are horribly suited for walking or grasping prey as their ancestors once used those arms for.
Oh, and I should clarify and amend myself. It's not quite true that evolution only goes forward. It also has some very limited side-to-side
movement via Horizontal Gene Transfer. While Horizontal Gene Transfer does take place in all species, it doesn't directly affect evolution. Rather,
it slightly reconfigures the DNA in a way that later mutations could cause a frame shift and allow for slight genetic variance.
A common example of this is ERVs which are genetic markers in our DNA code where ancient viruses had inserted their own genetic code - but never
activated to hijack the cell and reproduce itself. We also rely on the hundreds of different species of bacteria living in our gut to pick up new and
novel defenses for our immune system against microbial threats.
HGT happens quite prolifically in single-celled organisms... and far less so in multicellular organisms. Nor will being around cat or dogs trigger HGT
between you and your pet. So the tree of life is still very much intact, but slightly spider webbed in the upper branches, and dense interconnected in
the lowest levels.
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