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Set foot on the evolution of whales and dolphins

What preceded what - the loss of the ability to walk or the transition to a meat diet? A new comprehensive analysis sheds light on the origin of the marine mammals and their split from the family of ungulates whose living terrestrial relative is the hippopotamus

Ambulocetus natans - walking whale. A semi-terrestrial, semi-marine creature from the Eocene era. Illustration: Karl Boel
Ambulocetus natans - walking whale. A semi-terrestrial, semi-marine creature from the Eocene era. Illustration: Karl Boel

When the first ancestors of today's marine mammals - the whales and dolphins - dipped their toes in the water, a series of evolutionary changes began that eventually led to the marine iguanas becoming the largest group of ungulates.

However, the question is what was the first thing that happened, was it the changes in diet from a vegetarian diet to a meat diet, or the loss of the ability to walk? A new paper published this week in PLoS ONE resolves the issue through a massive data comparison of the morphology, behavior, and genetics of today's marine mammals and their first fossil relatives.

The ancestors of marine mammals probably entered the water before changing their diet (and their teeth) to allow carnivory. According to the reconstruction Indohyus, a semi-marine herbivore that lived 48 million years ago and the hippopotamus living today are the closest remnants in the evolutionary tree of the group of mammals to which marine mammals also belong.
If we only had classification categories of living things to determine the relationships within a group of animals, we would lose a large proportion of the diversity and part of the picture of what is going on," said Michelle Spaulding, the study's principal investigator and a research student at the American Museum of Natural History.

"The Indohyus are interesting because their fossils combine a vegetarian dentition with adaptations in the ear bones for underwater hearing traditionally associated only with whales."

Mammal researchers wonder how the line of dolphins evolved with the limbs adapted for conversation and the lack of hair. About sixty years ago, researchers first proposed that marine mammals are distant relatives of ungulates, specifically ungulates such as sheep, antelopes and pigs. In other words, the meat-eating killer whale and the fish-eating dolphins are descendants of a group of herbivorous animals. More recent studies have revealed that among the ungulates, hippos are the closest living land mammals to marine mammals.
Because no one would have discovered the kinship between hippos and whales based on their size, fossil evidence becomes an important tool in determining the exact evolutionary steps taken by the ancestors of marine mammals. Traditionally, marine mammals have been associated with the mesonychids, a group of long-extinct carnivores that had a single hoof. The recent discovery of Indohyus complicates the picture (as it always does with new fossils) because its ear bones are similar to those of modern marine mammals, and are theorized to help the animal hear better underwater.

To rule out a number of alternative evolutionary stories regarding the question of what came before what - the eating of meat or the adaptation to life in water, and to know whether the ancestor was the Indochius or the Mesonychid, Spaulding and her colleagues mapped the evolutionary relationships between over 80 species, some living and some fossils. The species were classified according to 661 morphological and behavioral characteristics (such as the presence of hair or the shape of the ankle bone).

49 new DNA sequences from five genes were also added to the mix, of over 47 thousand characteristics. Both the morphological and genetic data were modeled after previous analyzes by researchers Maureen O'Reilly of Stony Brook University and John Gatsev of the University of California, Riverside. In addition, Indochius, carnivores (dogs and cats) and an archaic group of carnivorous mammals known as crodonts were included in the model.

The team found that the less complicated evolutionary trees place the Indochiids and similar fossils close to whales while the mesonichids are more distantly related. Hippos also remain according to this study the closest living creatures. The results show that the ancestors of the marine mammals adapted to life in water before becoming carnivores, but that the carnivorous diet evolved while they could still walk on land.

According to O'Leary, the early whales - Indohyus, probably ate their prey in water but were still able to walk on land, Indohyus adapted to hear underwater but ate grass, while Ambulocetus, a walking whale that lived about 50 million years ago, ate meat.
There is a conflict deep in the evolutionary tree, says Spaulding. The backbone of the tree is strong and stable, but there is a fairly large group of animals that are classified into groups based on common features that indicate a common origin. We must carefully re-examine all the features of these animals and see which sets of features derived from different taxonomic categories solve the puzzle of the marine mammal evolutionary tree.

to the notice of the researchers

32 תגובות

  1. to Michael Rothschild.

    On second thought, the question you presented in response #30 can
    To be a good basis for research, which may support the theory
    which I present….

  2. A person:
    And since you are actually ready to think, I suggest you think about what you would prefer to see:
    A woman with a bikini or a woman with the negative of a bikini (that is, one whose whole body is covered with clothes and only her genitals are exposed).
    I ask you not to answer this question for me.

  3. A person:
    Contrary to what they are trying to sell you - all aquatic animals (but all of them!) have undergone an adjustment regarding the fur - whether it is the total shedding or whether it has turned into short and dense fur that is directed against the direction of swimming and is well lubricated.
    The feathers of birds that dive a lot - such as penguins - have undergone a similar adjustment.
    I am not here to defend the Aquatic Monkey theory, which I have no idea if it is true, but I suggest you take into account - apart from the above - also the fact that it is precisely the need to excel in swimming (and not the need to be liked by women who often prefer hairy men) that brings men so that they shave their bodies.
    Another interesting fact is the reflex that babies have that seals their trunk when underwater and allows them to dive without ever learning it.
    And regarding publication - writing a book is of course irrelevant.
    Harry Potter was also written and is a great success.
    Publishing is writing for a peer-reviewed scientific journal.

  4. And eventually, those marine mammals that lost their fur
    (whales and dolphins) also lost the ability to live on land
    – and that's the whole story.

  5. per person.
    Another thing. Just to emphasize how important fur is to mammals and their offspring
    is not necessarily related to swimming, it can be seen in the seals, who have gone through almost everything
    Possible adaptation for swimming: lost earlobes, gained fins
    And actually lost the ability to walk...and more...
    But they kept their fur.

    your conclusions.

  6. per person. Speaking of publishing, I'm currently working on an autobiographical book
    And in it I intend to deal, on the sidelines, with the evolutionary reasons for thoughts
    Suicides and suicides - as I understand them.

  7. For Adam (24) I read the reason for walking upright (living in the savannah) in the sources
    Many different (maybe even on this site), the reason for women's breast enlargement
    I learned (to the best of my memory) from Robert Ardrey's book "The Territorial Command"
    many years ago. By the way, I wholeheartedly recommend the book.
    The rest (removing the fur and attaching the skin to the body) is, as far as I know, a hypothesis
    Mine complements Ardrey's ideas in my opinion - although it is possible that she is mentioned
    Even at Ardari's - and I don't remember.

    D.A. I agree with your response to my opinions (ie: that there is no proof in everything I wrote
    unequivocally), but you should pay attention to the details, for example: unlike meerkats
    Apes do not have a tail, which can support the body when standing up.
    In the end, the explanation I present here exhausts all the changes, while
    that the aquatic ape theory (for that matter: a hominid upright in water) is not
    explains (for example) the absence of fur; You have to remember that very few have
    Warm-blooded animals (and certainly on land) have given up an inert cover (Vish
    There are probably many good reasons for this): fur or feathers that protect the skin
    Relatively thin. The water does not interfere with fur growth or require attachment
    The skin (e.g. certain dogs and polar bears swim long distances with fur
    thick) except in "extreme" cases - in swimming animals whose evolution
    in water millions of years old (which is obviously impossible, in terms of the timelines
    the evolutionary ones in humans), the second option, (ie: the adapted aquatic monkey
    Especially for swimming in water, if we ignore the schedules and the lack of membranes in the limbs
    for example) does not explain the human sight that is not adapted to water -
    And of course the woman's chest, which cannot be found in any other woman's body and certainly
    which does not contribute hydrodynamically.
    The explanation I present is also more logically correct (Occam's Razor): while
    that the aquatic monkey theory has no proof and this whole stage of development
    (deviation to swamp or sea life and return from it) is a hypothesis in Alma, after all the explanation
    Selfish bringer is coherent throughout.

    Regarding the publication. Since I am not an authority (evolutionary thought
    She's a hobby for me), I didn't invest enough to bring arguments to the claims
    that I bring up - and to find out if people conceived the explanation from beginning to end
    Others before me, it is unlikely in my opinion that there will be a newspaper that will be willing to publish
    Such a theory.

  8. to another:

    I repeat that I liked your explanation of the lack of fur.
    If it is yours, I would really look for a way to publish it, as Michael says.

    In contrast, the accepted explanations for walking on two always sounded silly to me.
    See from a distance: you don't have to stand up all the time. Look at the meerkats who put up a "keeper".
    Defend with the front limbs: you don't have to stand up at all. Look at the cats.
    The same goes for throwing stones: the chimpanzees you showed don't walk upright.

    Walking on two legs is no small matter, and animals that have switched to walking on two legs like the birds did so for a good reason.

    The Aquatic Ape Theory claims that our ancestors lived in an area of ​​swamps and shallow lakes.
    In such an area, walking upright, while keeping your head out of the water, is more economical than swimming.

  9. And by the way, I guess you won't have any trouble finding pictures of kangaroos on the Internet.

  10. totally someone:
    Enough with this bickering.
    I think you are missing out big time.
    I did not say that a clothed body has the same effect.
    Where did you get that from?
    I claim that this would have been the case even if humans had been covered with fur - even then they would have preferred naked (with fur) over clothing.
    But enough.
    Why is it so important for you to convince me?!
    Try publishing your opinion in a scientific journal and you will gain much more recognition.

  11. Dear Michael, if a body is covered with fur or clothes it creates the same effect
    Like a naked body, why do so many websites insist
    Post photos of naked girls? Why do people pay?
    So many watch women and men naked (when they are in vain
    can see and photograph them and their likenesses dressed in the street). Maybe you will
    Street poll on the topic: What is more sexually stimulating: a naked woman or
    Dressed - and the women, of course, the same question about the men:
    How are they more stimulating - clothed or naked?
    And to our point: it is clear that Matt is in the history of human evolution
    The sense of smell stopped being a dominant factor in choosing partners -
    And in my opinion, there is a close connection between walking on two feet, standing upright,
    Making the sense of sight the dominant factor in choosing partners,
    Attaching the skin to the body, breast augmentation in women and implants
    the fur
    I find no other reason for these changes in humans.

  12. Come on seriously!
    I know for what purpose these surgeries are used but it does not change the studies that were conducted.
    I did not claim that the chest has no role. He has a role and this role is less significant than the one you are trying to give him. And for some reason you decided to harness the chest to prove the fur thing. What is the connection? There is no connection!
    I have no problem admitting what I think is true, but your theory does not convince me, so I will not admit its correctness.
    How about trying to publish it in some scientific journal?

  13. to Michael I could go on and go into more details that strengthen you
    My opinion, except that I fear that instead of a conversation, an argument will develop here, which I have none of
    Intention to exhaust myself and you. It's clear to me that if you just check for yourself,
    Based on conversations with women, what exact need do the surgeries fill?
    For breast enlargement and lifting and how the men react to Maran before and after, you will understand
    That this time he was right with me.
    I can only hope you have the courage to admit it.

  14. And anyway - the idea of ​​wearing fur for sexual stimulation cannot draw confirmation from the behavior in clothes.
    When the fur was shed there were no clothes and for some reason it stayed in the more interesting places.

  15. incidentally:
    I don't remember the source, but I actually read a study on the looks that men give women and vice versa.
    The conclusion of the study was that most of the looks from both sides are directed to the buttocks.

  16. Completely:
    There you said it all.
    The chest can be seen even when fully clothed.
    What about full fur? Will she hide him?

  17. to Michael (14). The primary and most prominent predisposing factor is the size of the female breast,
    Pay attention to all the silicone surgeries (for what do you think so many women undergo
    them – while men spend a fortune to do the opposite?), the size
    The chest can be appreciated even when fully clothed, while the genitals are not anyway
    Seen fully clothed. What then has been causing you to think for thousands of years
    Men are attracted to women in human society (clothed most of the time)
    And in a subconscious and fulfilling way, the same role played by the sense of smell in dogs?
    If you are not sure, ask your friends what is the first thing
    which they examine when they see from some distance and behind a figure that is likely to be female
    (long hair, relatively wide pelvis); Without checking I'm willing to bet that the thing
    The next thing we will examine is the size of the chest, which will be the final approval for placing them
    – and ultimately the attraction factor.
    Speaking of which, the female breast is a kind of "semaphore" for female fertility:
    If it is flat, the woman has not yet reached sexual maturity or sexuality
    (and ultimately her fertility) is in doubt - and therefore should not attract; If
    It is full and large - the woman is of childbearing age and likely to be well nourished;
    If it falls - it is likely that the woman is at the age of menopause, or approaching it.
    In my opinion, the "Semaphore" subconsciously affects the attractiveness of the man
    To a woman, women recognize this and that is why so many surgeries are performed
    for breast enlargement and lifting.

    Regarding the kangaroo. Since I haven't seen Kanga (Roo's mother) yet
    I can't comment on your very wise comparison.

  18. Personally - the idea of ​​shedding the fur over the whole body (and leaving it specifically in the genital area) in order to expose the genitals seems absurd to me.
    The kangaroo thinks so too.

  19. per person (12). The accepted explanation is that the Syrian-African rift separated the
    Our ancestors who lived in North East Africa (Ethiopia, Horn of Africa)
    From the forested area that was west of the rift and caused climatic changes
    and for savannah conditions; When there were no trees to climb (and thus also to locate from afar).
    predators to escape from them) the hominids had to stand upright to locate food
    and large predators and free their hands to use them for defense or
    Attacking (also by using stones as chimpanzees do for example) and carrying food.

  20. To someone else entirely:
    Your explanation about the lack of fur is very nice.

    Do you have your own explanation for the reason for the switch to upright walking?

  21. For Adam (8), I know the theory, but I'm afraid it has nothing to do with reality.
    In my opinion, the human body is separate from fur hair because unlike dogs
    And monkeys, a creature that walks on two legs cannot recognize details (and no less
    Important: the gender of those individuals) in the flock according to observation or smell
    of their genitals. That's why women's breasts also grew - most of the material
    in which it is fat and not milk-producing organs - to facilitate mating and to avoid
    from mistakes….
    The theory I advocate also explains why, unlike the skin of monkeys
    And dogs, the human skin does not hang and separate from the body, not to mention that
    Hanging skin would interfere with the function of the limbs in a standing person. There is
    So-called "convergent evolution" - but this is not the case, otherwise
    We would find swimming membranes at least as in the dog breed
    "Newfoundland" - which did not go through the other adaptations for swimming like

  22. My father, killer whale is called Leviathan Katlan in Hebrew.

    Ami, are you familiar with the Aquatic Monkey Theory?

  23. A question for those who understand nothing
    Are there known aquatic species that feed only on plants?
    Where are there marine equivalents to the herbivores on land?
    Note: I am not referring to the levitans that feed on plankton.

  24. An important and interesting article, but with many spelling errors ("meat" probably instead of "meat")
    And confused descriptions: "...the early whales - the Indohyos, probably ate the
    Their prey was in the water but still able to walk on land, the Indochius adapted
    for hearing underwater but ate grass, while Ambulocetus
    A walking whale that lived about 50 million years ago, ate meat..."
    In other words: if "the Hindus, they probably ate their prey in water" (and the word "their prey"
    shows that they were meat eaters), why is it claimed in the following sentence that they ate grass? Why the transitions?
    The goddess between singular and plural? And what kind of creature is a "walking whale"?

  25. We are told that the beginning of life is in the water, and from there to the earth, and back to the water (I have not read the article). if I
    Understand correctly, in cases of acute ecological disasters, some of us will return to the water.
    Shouldn't it be worth encouraging and nurturing the growth of swimming membranes and a double respiratory system, like in amphibians? otherwise what
    The purpose of studies of the above type?
    I will mention again that I did not read the article. Oh yes, do you mean cloven hooves, or quadrupeds?
    And sorry for the true ignorance.

  26. But when you see the strong emotional bond they develop with humans, it is hard to rule out the possibility that their father was our best friend - the dog

  27. Very interesting article, thanks Abby.
    Two points that come to my mind right now:
    1) When it comes to creating trees of the origin of animals, I would be careful when it comes to clustering based on morphology. Today we do it a lot at the genome level. Sequences are compared and there are several methods for this. When it comes to calistor according to other parameters, methods must be found that will fit and anyway the whole issue of trees is controversial (the manner of its quantification and the meaning of a tree that does not contain all the elements of life and allows a partial view)

    2) The second thing that comes to my mind, and of course here I am wise at night saying the things only after reading the article above: it sounds very logical that the first animals to return to the water were the ravens who began to wade through the shallow waters and lick seaweed and from there they went deeper and learned to dive and went through developments related to swimming. Why does it make less sense that carnivores are the ones who entered the sea first? Because the carnivore deals with prey that can move, for the most part. And for that it is necessary to be able to move better than the prey. It is unlikely, in my opinion, to assume that a terrestrial predator can deal with an aquatic prey (imagine yourself, even though you know how to swim, trying to catch a fish in the water with only your hands).

    In the end, the article is interesting but its claims are based on an incomplete picture and therefore should be treated with caution

    Greetings friends,
    Ami Bachar

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