Page 1 of 2 12 LastLast
Results 1 to 30 of 32

Thread: Bipedalism is not especially difficult to achieve.

  1. #1

    Lightbulb Bipedalism is not especially difficult to achieve.

    Watch a bipedal cat.

    http://www.youtube.com/watch?v=5YCm03wV8dw

    It certainly seems that bipedalsm is not especially hard to achieve. The last time the pre apes did it; 2, milion years ago; it gave rise to man. Seems like if the movie was run again; it might have happened to the cat species. Giving rise to Catkind. Is there already a Catkind out there on those trillion "Earths" in our galaxy. The large numbers would suggest it.

  2. #2
    Join Date
    Jul 2004
    Posts
    398
    Cats would suck at tool-making.

  3. #3
    Join Date
    Jan 2008
    Posts
    4,302
    Bipedalism may or my not be easy, but it's hardly a sure thing for intelligence. All birds are bipeds, and only a few of them are even close.
    On the other hand,many Cephalopoda are about as far from bipedal as you can get, yet are very intelligent. Among the things needed, in my view, for a intelligent life, more important then bipedalism in my opinion, is a set of manipulators. A manipulator could be an extended proboscis, a claw and beak combination, tentacles, the classic fingers thumb combination, or something else entirely. A manipulator must be versatile. While not as good at a specific task as some appendages, it must be at least adequate at many.

  4. #4
    That cat reminded me of Ardi; (Ardepithicus); it already has a substantial brain; standing up alllows the hands to evolve into efficient manipulators....and the brain to increase in complexity

  5. #5
    Join Date
    Jan 2008
    Posts
    4,302
    But standing up has to have a use first, or it wouldn't evolve. Primates already had pretty dexterous manipulators before they went all bipedal. A felis catus is a successful hunter, as feral cats show. If it needs to carry things around, it's mouth is adequate for its needs, carrying prey and young.

  6. #6
    Join Date
    Mar 2003
    Location
    Calgary Alberta
    Posts
    1,074

    Talking

    Quote Originally Posted by ravens_cry View Post
    But standing up has to have a use first, or it wouldn't evolve. Primates already had pretty dexterous manipulators before they went all bipedal. A felis catus is a successful hunter, as feral cats show. If it needs to carry things around, it's mouth is adequate for its needs, carrying prey and young.
    Maybe, as Richard Dawkins writes, the first of our ancestors to stand up did so to show off their nasty bulbus parts.

  7. #7
    Join Date
    Jan 2008
    Posts
    4,302
    Quote Originally Posted by snowcelt View Post
    Maybe, as Richard Dawkins writes, the first of our ancestors to stand up did so to show off their nasty bulbus parts.
    Do you mean our genitals? From what I understand, male human genitals are rather oversized for our body size compared to other mammals. My theory is they grew so large because bipedalism makes them so displayable, like a turkeys wattle or a peacocks tail feathers. As for bipedalsim, no idea. Meerkats stand up for long periods of time, but it isn't their main mode of locomotion.

  8. #8
    Quote Originally Posted by ravens_cry View Post
    Do you mean our genitals? From what I understand, male human genitals are rather oversized for our body size compared to other mammals. My theory is they grew so large because bipedalism makes them so displayable, like a turkeys wattle or a peacocks tail feathers. As for bipedalsim, no idea. Meerkats stand up for long periods of time, but it isn't their main mode of locomotion.

    Will they start shrinking now that clothes make them not on display, or is that something females can see past in determining who they mate with?

  9. #9
    Join Date
    Jan 2008
    Posts
    4,302
    Quote Originally Posted by Canis Lupus View Post
    Will they start shrinking now that clothes make them not on display, or is that something females can see past in determining who they mate with?
    Possibly. It would be an interesting study. Still, many men, and some woman, do have a preoccupation with size, despite the fact it makes absolutely no difference in the actual use in any form of sexual activity. Other anecdotal evidence is the sheer, literal, lengths, human males have gone to with the invention of codpieces.[likely NSFW]

  10. #10
    Join Date
    Jan 2008
    Posts
    2,541
    Quote Originally Posted by ravens_cry View Post
    But standing up has to have a use first, or it wouldn't evolve. Primates already had pretty dexterous manipulators before they went all bipedal. A felis catus is a successful hunter, as feral cats show. If it needs to carry things around, it's mouth is adequate for its needs, carrying prey and young.
    Becoming bipedal would, in all likelihood, be actively harmful to a cat's hunting abilities; they're well adapted to quadrupedal running, but lack any obvious preadaptions for bipedality.

    In primates, bipedality arose from climbing. In birds' ancestors, it probably arose did arise as an adaption for faster running, but the ancestors in quesition (things like Euparkeria) were rather different from cats in their locomotor patterns - in particular, they'd been affected by Carrier's constraint, which hurts quadrupedal running but that mammals have circumvented by evolving parasagittal gaits. Neither represents an evolutionary pathway likely to be followed by cats.

    Among primates themselves, there's no strong correlation between bipedality and intelligence; sure, humans are the most bipedal and the most intelligent, but the next most bipedal ones are the lemurs and the gibbons, who rank rather further down on the intelligence scale.

  11. #11
    Join Date
    Feb 2009
    Posts
    810
    Bipedal, quadripedal, but not a single tripedal animal... Why does all (well, nearly) biology have either radial or bilateral symmetry?

  12. #12
    Join Date
    Jan 2008
    Posts
    2,541
    Quote Originally Posted by chrlzs View Post
    Bipedal, quadripedal, but not a single tripedal animal... Why does all (well, nearly) biology have either radial or bilateral symmetry?
    Given the success of pentaradial echinoderms, I would think that the lack of triradial organisms* is an evolutionary accident. When it comes to specifically tripedal animals, the immediate reason would seem to be that the animals that evolved legs - vertebrates and arhtropods - were bilaterial, which make even numbers of legs natural.

    As for the popularity of bilaterality, it's no doubt because it's practical when you're moving about - you have a front end with sensory organs to see where you going, and a rear end which dumps stuff you don't what anymore, and the influence of gravity and sunlight in many habitats makes having separate upsides and downsides convenient, but there's usually little reason to distinguish right from left (humans are unusually asymmetric in this regard, and we're pretty symmetric still). Moving about is also the motivation for having legs, which may help explain why they're restricted to bilaterian animals. (Or mostly restricted, if we consider sea star and snake star arms to qualify as "legs" - these too are motile animals.)


    * The lack is not necessarily complete - some Ediacaran and Palaeozoic problematica appear to have triradial symmetry. And there's probably some triradial unicells somewhere just to keep things from being tidy.

  13. #13
    Join Date
    Jul 2008
    Posts
    1,550
    In After Man, Dougal Dixon visualized an evolutionary trail from small cats that had evolved for total arboreality (is that even a word?). A kind of feline gibbon, if you like. It would be semibipedal in any case.

    ---

    Quote Originally Posted by AndreasJ View Post
    Given the success of pentaradial echinoderms, I would think that the lack of triradial organisms* is an evolutionary accident. When it comes to specifically tripedal animals, the immediate reason would seem to be that the animals that evolved legs - vertebrates and arhtropods - were bilaterial, which make even numbers of legs natural
    This is along the lines my thinking goes as well. Tripedal land animals would have a certain amount of balance problems when moving, but I don't see this as an invariably fatal flaw that would make an even number of legs an "evolutionary imperative".
    The dog, the dog, he's at it again!

  14. #14
    Join Date
    Jan 2008
    Posts
    2,541
    Quote Originally Posted by tnjrp View Post
    arboreality (is that even a word?)
    If it weren't, you'd just made it one! But it's been around for a while and is listed in at least some dictionaries.

  15. #15
    Join Date
    Nov 2005
    Posts
    5,450
    Quote Originally Posted by chrlzs View Post
    Bipedal, quadripedal, but not a single tripedal animal...
    Kangaroos walk in a tripedal fashion--the stiff tail is used as a third leg. Some birds, like tree creepers, also use stiff tails as an extra foot.
    Why does all (well, nearly) biology have either radial or bilateral symmetry?
    Actually, the majority of biology lack either radial or bilateral symmetry.

  16. #16
    Join Date
    Jan 2004
    Posts
    1,505
    No one is going to mention the Kzin?

  17. #17
    Join Date
    Jan 2008
    Posts
    2,541
    Quote Originally Posted by IsaacKuo View Post
    Kangaroos walk in a tripedal fashion--the stiff tail is used as a third leg. Some birds, like tree creepers, also use stiff tails as an extra foot.

    Actually, the majority of biology lack either radial or bilateral symmetry.
    By species number, the majority of known diversity are bilaterally symmetric animals, mostly arthropods.

    By individual number, bacteria win but lots of those are radially symmetric. Do you have a reference for the amorphous (or differently-symmetrical) ones being the majority?

  18. #18
    Join Date
    Nov 2005
    Posts
    5,450
    I was actually thinking of plants, which I had assumed (without really thinking about it) would be the majority of life on Earth because of the way the ecological pyramid gets smaller as you go up a level.

  19. #19
    Join Date
    Jun 2003
    Posts
    8,571
    The bacteria in the soil, in water and in the deep hot biosphere probably outweigh and definitely outnumber plants. And many bacteria are radially symmetrical.

  20. #20
    Join Date
    Jan 2008
    Posts
    2,541
    Quote Originally Posted by IsaacKuo View Post
    I was actually thinking of plants, which I had assumed (without really thinking about it) would be the majority of life on Earth because of the way the ecological pyramid gets smaller as you go up a level.
    I guess they win on biomass (the other contender would be bacteria), but most plants are approximately radially symmetric anyway. (No organism is absolutely symmetric of course, and many animals we conventionally describe as radially symmetric are more strictly actually tetraradiate, such as jellyfish. Most plants should be comparable to them in "radiality" I recon.)

  21. #21
    Join Date
    Jun 2003
    Posts
    8,571
    Quote Originally Posted by Daffy View Post
    No one is going to mention the Kzin?
    I'll mention them
    The Kzin were described by Larry Niven as evolving from 'plains cats'; but in reality there would be no cats on an alien planet. There may be cat-like animals, or to be even more pedantic, cat-like animal-like organisms, but the degree of resemblance to Earth cats is likely to be quite small.

    Niven seems to be quite aware of this- his Kzin are described as having 'parasol-like ears', 'a pink, rat-like tail', and a complex skeleton that is not closely similar to that of Earth mammals. I think that describing them as 'cats' is a literary device to make the reader accept them as less alien; in fact the Kzin (as described in the books) are not really all that cat-like.

  22. #22
    Join Date
    Jan 2008
    Posts
    4,302
    People like naming things that that vaguely resemble something else in some way. Such a meerkats, ring-tailed cats, toddy cat, and other creatures that are not cats, but we named such. I am sure if we find complex life on another world with four to six legs, a long tail, a shortish muzzle, and catches small prey, we will call it cat of some kind.

  23. #23
    Join Date
    Jan 2004
    Posts
    1,505
    Quote Originally Posted by eburacum45 View Post
    I'll mention them
    The Kzin were described by Larry Niven as evolving from 'plains cats'; but in reality there would be no cats on an alien planet. There may be cat-like animals, or to be even more pedantic, cat-like animal-like organisms, but the degree of resemblance to Earth cats is likely to be quite small.

    Niven seems to be quite aware of this- his Kzin are described as having 'parasol-like ears', 'a pink, rat-like tail', and a complex skeleton that is not closely similar to that of Earth mammals. I think that describing them as 'cats' is a literary device to make the reader accept them as less alien; in fact the Kzin (as described in the books) are not really all that cat-like.
    I can't believe this prompted a debate!

    But it was Chmee himself who described his ancestors as "Plains Cats." And in a literary sense, much of Chmee's movements and motives seem based on what would happen if a race of cats became sentient. I am hesitant to claim to know what was in Niven's mind...but I think you are mistaken. Kzin are sentient cats.

  24. #24
    Join Date
    Jun 2003
    Posts
    8,571
    I do disagree, for many reasons. Kzin (if they existed) would be sentient 'cat-like, animal-like organisms'.

    They are not cats, as taxonomically there are no members of the cat family on any planet other than Earth. There are also no mammals anywhere else in the universe; strictly speaking there are no animals (as in 'members of the Earth kingdom Animalia) anywhere else in the universe. Certainly there may be heterotrophic mobile multicellular organisms elsewhere in the universe, but they won't be true animals. Taxonomically it will be necessary to come up with new names for all these new kingdoms, phyla. classes, orders and species (assuming the taxonomic patterns are the same, which may not be the case).

    For the Kzin, or for any cat-like organisms we might encounter one fine day on another planet, I would suggest terms like 'felinoid' or 'feliniform' rather than identifying them too strongly as 'cats'. I suppose we would quite quickly run out of such derivative labels - but only if we find several planets each with separate families of cat-like organisms; and the chances of that seem very slim indeed.

    Remember that meerkats, ring-tailed cats, and bearcats are all very closely related to cats, comparatively speaking; they each share large portions of the same genome. Any hypothetical feliniform from Tau Ceti would not share any common genetic heritage with the cats of Earth.

  25. #25
    Join Date
    Jul 2008
    Posts
    1,550
    Peter F. Hamilton (maybe others as well) uses a handy term "x-analogue". So the Kzin would be humanoid "cat-analogues".

    On tripedalism issue, kangaroos and the aforementioned gibbons do use vaguely tripedal means of locomotion and some dinosaurs may have as well. But obviously they aren't truly tripedal animals. I can't think of a very good reason why such would evolve in an environment where they face stiff competition from quadrupeds (and in rare cases, bipeds), tho I've not yet seen a really good objection to there being a potential for initially tripedal fauna either.
    The dog, the dog, he's at it again!

  26. #26
    Join Date
    Jul 2004
    Posts
    398
    Quote Originally Posted by eburacum45 View Post
    ....strictly speaking there are no animals (as in 'members of the Earth kingdom Animalia) anywhere else in the universe. Certainly there may be heterotrophic mobile multicellular organisms elsewhere in the universe, but they won't be true animals....
    Across the solar system, the terms 'volcano', 'cyclone', etc. are used for phenomena that fit the definitions of the same phenomena on Earth.

    If ET life forms are found, I could well see them, in some cases, fitting into the general definitions for bacteria, plants, or animals. They would of course belong to separate taxonomic groups than those on Earth. I think limiting the use of the term 'animal' to "members of the Earth kingdom Animalia" would be too strict. It would be like requiring a different term for volcanoes on Mars.

  27. #27
    Join Date
    Jun 2003
    Posts
    8,571
    There is a difference between the common name of an organism and its classification, so it seems quite likely that 'mobile heterotrophic multicellular organisms' will sometimes, or usually, be called 'animals'. Not all mobile forms will be 'anmals' however; I'm sure that evolution will be more devious than that. Mobile slime-mold like creatures, mobile plant-like creatures, megascale amoeba, mobile colonies of bacteria-like organisms, creatures evolved from long-abandoned self-replicating machines over billions of years - we may encounter any of these, and even stranger things. But none of them will be members of the Earth taxon 'Animalia'.

    This wild and as-yet hardly expected diversity which I would expect to find out there seems unlikely to produce many creatures which we would ever be comfortable labelling as 'cats', in my opinion. Far too many parochial evolutionary events have combined to create the felines of Earth, and even if we encounter a four-legged (or two-legged) cat-analogue on an extrasolar planet, it is almost totally impossible that each of those events have been replicated in the evolution of that creature. So,(as Niven has described in the case of the Kzin) you might get a creature which looks superficially like a cat, but the details will be very different (ears, tail, bonestructure, bipedal stance).

    One parochial feature that is unlikely to be exactly replicated is the mammalian jaw. Only vertebrates have structures like this; it is quite likely that our hypothetical cat-analogue would have Predator-like mandibles rather than a hinged and fused opening muscular flap with mammal-like dentition. But the facial structure of a cat is very distinctive due to that jaw-line and dentition; would we be happy to call a tetrapod predator with a set of specialised mandibles at the caudal end a cat? I don't think so.

  28. #28
    Join Date
    Jul 2004
    Posts
    398
    Quote Originally Posted by eburacum45 View Post
    ...This wild and as-yet hardly expected diversity which I would expect to find out there seems unlikely to produce many creatures which we would ever be comfortable labelling as 'cats', in my opinion....
    Not to argue, but to point out an interesting quirk of humans. We easily classify things based on the superficial. There is, after all, a Crab nebula. : )

  29. #29
    Join Date
    Nov 2005
    Posts
    5,450
    That suggests a way for the Kzin to be called "cats"--maybe the first sitings of them were fuzzy, through a telescope (or backwards glances from the lucky few who escaped).

    Alternatively, maybe it's the Kzin who claim to be descended from "cats". To them, Earth cats remind them of their ancestors.

  30. #30
    Join Date
    May 2007
    Location
    Earth
    Posts
    10,239
    What does a cat walking on its hind legs have to do with anything? It's a fairly common trick for dogs, and anybody who has seen goats browsing has certainly seen bipedalism in nature. Goats have also been known to climb trees, but I digress.


    Quote Originally Posted by Daffy View Post
    I can't believe this prompted a debate!

    But it was Chmee himself who described his ancestors as "Plains Cats." And in a literary sense, much of Chmee's movements and motives seem based on what would happen if a race of cats became sentient. I am hesitant to claim to know what was in Niven's mind...but I think you are mistaken. Kzin are sentient cats.
    SF authors are allowed certain liberties, and Niven used quite a bit with the Kzin, and his other ETs. CJ Cherryh used roughly the same amount in with her Chanur, who are equally cat-like but (in my opinion) less cartoon-ish than the Kzin.
    Information about American English usage here and here. Floating point issues? Please read this before posting.

    How do things fly? This explains it all.

    Actually they can't: "Heavier-than-air flying machines are impossible." - Lord Kelvin, president, Royal Society, 1895.



Similar Threads

  1. Bipedalism in non-primate animals?
    By Inclusa in forum Off-Topic Babbling
    Replies: 6
    Last Post: 2011-Jan-29, 03:37 PM
  2. Bipedalism in other animals
    By newmac in forum Life in Space
    Replies: 51
    Last Post: 2009-May-23, 02:07 PM
  3. How do you achieve orbit around Mercury?
    By spaceboy0 in forum Astronomy
    Replies: 3
    Last Post: 2008-Jan-16, 11:30 PM
  4. What do we hope to achieve?
    By afterburner in forum Off-Topic Babbling
    Replies: 9
    Last Post: 2007-Jan-22, 01:58 PM
  5. Big Achievement Yet To Achieve
    By suntrack in forum Universe Today
    Replies: 0
    Last Post: 2004-Jun-19, 11:07 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •