palmer@cit-vax.Caltech.Edu (David Palmer) (04/19/86)
Organization : California Institute of Technology Keywords: dinosaurs, bipedalism, hunting, escape One advantage that humans have, which is primarily due to their bipedalism, is the ability to walk and run at a wide variety of gaits. A hunting human can eventually catch up with just about any animal, (assuming that it doesn't hide or burrow) just by walking at a pace that the prey cannot use efficiently. Of course, this doesn't help if you are being chased by a cheetah, but if you are chasing an impala, you can eventually tire it out and catch up with it David Palmer
friesen@psivax.UUCP (Stanley Friesen) (04/21/86)
In article <32@sphinx.UChicago.UUCP> Beth Christy writes: >[] > > Humans have no natural enemies and hence do not need >the speed advantage for survival. I'm under the impression (although I >could, of course, be wrong) that there were no species which preyed on >the bipedal dinosaurs either (or if there were, escape was not the >dinosaurs' defense). > Much of this is simply not true. Many herbivorous dinosaurs of the group known as Ornithopods are bipedal and lack any defense except running. Examples include such famous forms as Camptosaurus and Hypselophodon. And while modern Humans have no natural enemies, the earliest Hominids *did*, and they were already bipedal. Our current lack of predators is due to our success, not the other way around. -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ttidca!psivax!friesen@rand-unix.arpa
friesen@psivax.UUCP (Stanley Friesen) (04/21/86)
In article <204@spar.UUCP> ellis@spar.UUCP (Michael Ellis) writes: >>>Evolution is undirected: ie. it has no long-term goals. > > Survival? Existence? > Those are not really "goals" they are more like mechanisms. > > Few, if any, animals are as DANGEROUS as humans skilled in the use a > club or projectile -- witness the accuracy and power of a typical baseball > batter or pitcher. Or as utterly vindictive as a tribe of Humans one of whose members has been killed. > Chimpanzees, in fact, sometimes use sticks in self-defense. The > effectiveness of such tactics seems to be quite limited for knuckle > walkers. Some argue that our bipedalism evolved simultaneously as our > increasing reliance on balance transformed what began as an occasional > defense mode into a devastating form of attack. > An additional point. By this argument Human bipedalism becomes a very effective adaption to *carnivory*! In fact it seems to have appeared about the time our ancestors shifted from minimal utilization of meat as a dietary supplement(as in Chimpanzees) to deliberate hunting for meat as a major portion of the diet(Australopithecus). -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ttidca!psivax!friesen@rand-unix.arpa
friesen@psivax.UUCP (Stanley Friesen) (04/21/86)
In article <2529@jhunix.UUCP> (Thomas Richard Holtz) writes: > >Basically, the best palaeontological explaination for why dinosaurs were >bipedal and most mammals aren't boils down to: > > Why were most dinosaurs bipedal? > Because they evolved from bipeds (the thecodonts). > > Why are so few mammals bipeds? > Because they evolved from quadropeds (the therapsids). > >I know it's not a very exciting answer, but don't complain to me. >Complain to Mother Nature; she made the rules. :-) > Yes, quite correct, at least as far as we can tell with current data. However this only moves the question back one step. Why were thecodonts bepedal and therapsids quadrupeds? Actually I think this may have a more "satisfying" answer. That is my studies suggest that there were adpative reasons for the shift to bipedalism among thecodonts. But I will refrain from saying what I think until other people have had a chance to speak. -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ttidca!psivax!friesen@rand-unix.arpa
beth@sphinx.UChicago.UUCP (JB) (04/22/86)
[If God had wanted us to go around naked, we'd have been BORN that way.] In article <1109@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes: >In article <32@sphinx.UChicago.UUCP> Beth Christy writes: >>[] >> >> Humans have no natural enemies and hence do not need >>the speed advantage for survival. I'm under the impression (although I >>could, of course, be wrong) that there were no species which preyed on >>the bipedal dinosaurs either (or if there were, escape was not the >>dinosaurs' defense). >> > Much of this is simply not true. Many herbivorous dinosaurs >of the group known as Ornithopods are bipedal and lack any defense >except running. Examples include such famous forms as Camptosaurus and >Hypselophodon. And while modern Humans have no natural enemies, the >earliest Hominids *did*, and they were already bipedal. Our current >lack of predators is due to our success, not the other way around. My mistake - sorry for the misinformation. Just out of curiosity, what creatures preyed on early Hominids, and how do we know? Same question(s) for Ornithopods. (Sorry for my ignorance here - I'm just a casual reader.) -- --JB ((Just) Beth Christy, U. of Chicago, ..!ihnp4!gargoyle!sphinx!beth) All we learn from history is that we don't learn anything from history.
krista@ihuxe.UUCP (K.J.Anderson) (04/22/86)
<>
There is another good reason why more mammals have not developed
bipedalism. Pregnancy is more difficult for the biped. She
has only 2, not 4, legs to support the extra weight. Also there is
a horizontal component of force on her spine as well as the vertical
component. The strain on the biped's back while pregnant is
significant; ask any human mother! And finally, miscarriage is more
likely since gravity is pulling the fetus against the cervix.
These factors are irrelevant to reptiles and birds since they lay
eggs. So now I'm wondering about marsupials, particularly the
kangaroo. Her joey is born while still an embryo and completes its
development in the pouch. This would alleviate the miscarriage
problem, but it seems that the mother would still have the leg and
back problems.
As far as nature is concerned, our lives need not be perfect or
even pleasant - just survivable.
This is all musings and conjecture, of course.
ihnp4!ihuxe!krista
--
ihnp4!iham1!krista oh,i'llgetflamedtheni'llcryoh,dearfriesen@psivax.UUCP (Stanley Friesen) (04/23/86)
In article <71@sphinx.UChicago.UUCP> beth@sphinx.UUCP (JB) writes: > >My mistake - sorry for the misinformation. Just out of curiosity, >what creatures preyed on early Hominids, and how do we know? Lions, Hyenas, and Sabre-toothed cats. We know because we have found a number of early hominid bones with tooth-marks on them which match these species. One rather remarkable Autralopithecus skull has four holes in it space just right for the canines of some known carnivore(a Sabre-tooth I think). Apparently the cat had dragged the Ape-man by it head to its lair to eat it! > Same >question(s) for Ornithopods. (Sorry for my ignorance here - I'm >just a casual reader.) > With the Ornithopods it depends on *which* ones and when. Among the predators on these forms were such animals as Tyrannosaurus, and Deinonychus. It is also possible that Allosaurus preyed on some members of the group. How do we know? Well, tooth-marked bones are known for dinosaurs too. Also, at least some Ornithopods showed flock nesting behavior(some mass nest sites have been preserved, there was a Scientific American article on this last year). This kind of nesting behavior in living animals is usually a form of defense against predators. Then of course there is the evidence of the speed adaptions, such as long legs, weight supported on the toes, and light build, in certain small ornithopods(Dryosaurus, Hypselophodon &c), again usually associated with escape from predation in living *herbivires*. It is also possible that the heavy, spiked thumb of Iguanodon was a defense mechanism against predation. -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ttidca!psivax!friesen@rand-unix.arpa
chris@toram.UUCP (Chris Robertson) (04/24/86)
In article <1287@ihuxe.UUCP> krista@ihuxe.UUCP (K.J.Anderson) writes: > > ...The strain on the biped's back while pregnant is >significant ... > These factors are irrelevant to reptiles and birds since they lay >eggs. So now I'm wondering about marsupials, particularly the >kangaroo. Her joey is born while still an embryo and completes its >development in the pouch. This would alleviate the miscarriage >problem, but it seems that the mother would still have the leg and >back problems. Although kangaroos are bipedal, they actually spend a lot of time on all fours while grazing,* or lying on their sides resting. Upright stance is normally taken during running (hopping, actually), and when sitting up on their haunches looking about. Otherwise, 'roos are pretty laid-back creatures (pun intended). Hence, the joey is mostly carried slung under the mother's body, and when she sits up, the pouch is actually resting on the ground. So they don't have the same sort of strain on the lower back that people do. A baby 'roo is so tiny at birth (less than 1") that its weight is negligible. Joeys, however, still like to cram into the pouch when all they can fit inside is their behind, with head and legs hanging out in a tangle! * back legs are taking the weight, front ones used mainly for balance, but body posture is essentially horizontzal. -- Christine Robertson {ihnp4,linus,decvax}!utzoo!toram!chris An apple a day keeps the doctor away, especially if aimed well.
ins_atrh@jhunix (04/29/86)
In article <71@sphinx.UChicago.UUCP> beth@sphinx.UUCP (JB) writes: >My mistake - sorry for the misinformation. Just out of curiosity, >what creatures preyed on early Hominids, and how do we know? Same >question(s) for Ornithopods. (Sorry for my ignorance here - I'm >just a casual reader.) >-- >--JB ((Just) Beth Christy, U. of Chicago, ..!ihnp4!gargoyle!sphinx!beth) > > All we learn from history is that we don't learn anything from history. As with almost all of paleontology, we don't *KNOW* (as in 100% certain) anything. However, we can make pretty good guesses: in the Holocene (that's "now" for those of you who aren't into geological time) the big cats, wolves, and similar types prey upon primates (including the occasional humans). In the fossil record of the Pliocene and Pleistocene we find the remains of big cats, wolves, other hunters, and hominids. By comparative ecology (and using the tooth marks found on a few hominids) we can make a very good hypothesis that these creatures ate our ances... er (better make this safe for the Net, Tom :-)) that is, the hominids. The ornithopods were most certainly hunted by the carnosaurs, the family of carnivorous dinosaurs that included the tyrannosaurs, megalosaurs, and similar hunters. We have found many tooth- and claw-marks on ornithopod bones, and there are even tracks of ornithopods being chased by theropods (trivial point: the classic record of a chase scene, from Texas, I believe, does not have an ornithopod starring as the prey, but rather a sauropod [one of the long necked, heavy dinosaurs like "_Brontosaurus_"). Thomas R. Holtz, Jr. JHU Department of Earth and Planetary Sciences "If history repeats itself, why is there so much of it?"
michaelm@bcsaic (04/29/86)
In article <397@cit-vax.Caltech.Edu> palmer@cit-vax.UUCP (David Palmer) writes: >A hunting human can eventually catch up with just about any animal, >(assuming that it doesn't hide or burrow) just by walking at a pace >that the prey cannot use efficiently. Of course, this doesn't help >if you are being chased by a cheetah, but if you are chasing an impala, >you can eventually tire it out and catch up with it I'd heard this before (in Analog, a science fiction/ science fact magazine), but I had/ have trouble believing it. Has it ever *really* been "proven"? What's the original source? -- Mike Maxwell Boeing Artificial Intelligence Center ...uw-beaver!uw-june!bcsaic!michaelm
michaelm@bcsaic (04/29/86)
In article <2529@jhunix.UUCP> ins_atrh@jhunix.ARPA (Thomas Holtz) writes: >...Actually, this should read, "Humans can now hold *predators* at bay." >For several reasons. First, "enemies" can be construed to include poisonous >snakes which do not prey on humans (and which can take quite a toll in >Africa and Asia) as well as multitudinous parasites. This is just an aside, but there is a tribe in Ecuador called the Waorani (their name for themselves--they're more often referred to as the "Aucas", a word in another language that means "savages"). According to a survey done a few years ago, over 95% of the adult men had been bitten by poisonous snakes. This was before the advent of modern medical treatments for snakebite. Apparently the human body can hold its own agains a number of poisonous snakes... I don't know what permanent affects the snakebites had, although these men continued to lead active lives as hunters afterwards. -- Mike Maxwell Boeing Artificial Intelligence Center ...uw-beaver!uw-june!bcsaic!michaelm
michaelm@bcsaic.UUCP (michael maxwell) (04/30/86)
In article <1180@umcp-cs.UUCP> mangoe@umcp-cs.UUCP (Charley Wingate) writes: >Jane Goodall found that one of her chimps, having a weakened arm from polio, >had adapted by using walking much more than is ordinary for chimps. This >suggests the reason for bipedalism; the more hands become useful as hands, >the poorer they perform as feet. If I may revert to my original question, I agree that there is a lot of "reason" for bipedalism. In addition to the usefulness of hands as hands, I had heard it alleged that bipedalism was "useful" to the dinosaurs as a means of running faster, i.e. bipeds are (in general?) faster than quadrupeds. The question then was, why aren't more mammals (outside of man and kangaroos, and chimps with polio) bipeds? Bipedalism arose in two orders of dinosaurs (or at least so I thought--more on this in the next paragraph), while it is almost nonexistent in mammals. If bipedalism is so useful, why is it so rare today? One poster (I've seen a quote of part of his article, but not the original) said that the dinosaurs arose (no pun) from ancestors which were already bipedal, whereas the mammals arose (declined?) from quadrupedal ancestors. If this is true, then I was incorrect in thinking that bipedalism arose (independently) in two orders of dinosaurs, and this is probably all the explanation I need. -- Mike Maxwell Boeing Artificial Intelligence Center ...uw-beaver!uw-june!bcsaic!michaelm
g-rh@cca (05/03/86)
In article <> michaelm@bcsaic.UUCP (michael maxwell) writes: >In article <397@cit-vax.Caltech.Edu> palmer@cit-vax.UUCP (David Palmer) writes: >>A hunting human can eventually catch up with just about any animal, >>(assuming that it doesn't hide or burrow) just by walking at a pace >>that the prey cannot use efficiently. Of course, this doesn't help >>if you are being chased by a cheetah, but if you are chasing an impala, >>you can eventually tire it out and catch up with it > >I'd heard this before (in Analog, a science fiction/ science fact magazine), >but I had/ have trouble believing it. Has it ever *really* been "proven"? >What's the original source? I don't have sources at hand, but it's probably true. Apaches used to catch horses by walking them down. It was an all day proposition, but the Apache could go all day at an average pace that a grass grazing horse cannot maintain. The high speed predators (cheetah, impala, et. al.) can run at impressive speeds, but they can't maintain them for very long. My recollection is that the cheetah can hit 70 mph but can only maintain that speed for a few hundred feet. Richard Harter, SMDS Inc.
evans@mhuxt (05/05/86)
For those of you interested in the subject I suggest readings on pygmy
chimps (Pan paniscus). They appear more similar to humans than the common
chimp and, interestingly, use more bipedal locomotion. Interestingly, they
do so in trees. Please, also remember that a tree-dwelling lifestyle can
be very condusive to the pre-adaptation of an upright carriage. Suggest
reading Randall Susman's work on Australopithecine hands (in particular,
A. afarensis) which indicates that they still made ample use of trees. This
is followed by plain logic which notes that useing trees for sleep or escape
can be helpful in a large number of preditor avoidance situations.
How about a new subject in hominids. I'd like to see a discussion of
conditions which would be condusive to birthing totally dependent infants
(besides the obvious birth cannal/ bipedal locomotor efficiency statement).
For example, does anyone know of any animals with dependent infants which does
NOT find a way of storing them away in a shelter of eyrie at times? How many
do NOT have a support group (mate, troop,etc)?
Sukie Crandallfriesen@psivax.UUCP (05/15/86)
In article <7648@cca.UUCP> g-rh@cca.UUCP (Richard Harter) writes: > > The high speed predators (cheetah, impala, et. al.) >can run at impressive speeds, but they can't maintain them for very long. >My recollection is that the cheetah can hit 70 mph but can only maintain >that speed for a few hundred feet. > Quite correct. In fact, if the Cheetah fails to catch its prey it is down and out for many hours "catching its breath" before it can try again!(reference - last month's Scientific American). -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ??
friesen@psivax.UUCP (05/19/86)
In article <533@bcsaic.UUCP> michaelm@bcsaic.UUCP (michael maxwell) writes: > >If I may revert to my original question, I agree that there is a lot of >"reason" for bipedalism. In addition to the usefulness of hands as hands, I >had heard it alleged that bipedalism was "useful" to the dinosaurs as a means >of running faster, i.e. bipeds are (in general?) faster than quadrupeds. The >question then was, why aren't more mammals (outside of man and kangaroos, and >chimps with polio) bipeds? Bipedalism arose in two orders of dinosaurs (or at >least so I thought--more on this in the next paragraph), while it is almost >nonexistent in mammals. If bipedalism is so useful, why is it so rare today? > A large part of the answer comes from realizing that there is more than one solution to any problem. For every problem that bibedalism can solve there is also a solution based on a quadrupedal gait. This multiplicity of solutions is so widespread that it is cited as a principle of evolution by some authors. >One poster (I've seen a quote of part of his article, but not the original) >said that the dinosaurs arose (no pun) from ancestors which were already >bipedal, whereas the mammals arose (declined?) from quadrupedal ancestors. >If this is true, then I was incorrect in thinking that bipedalism arose >(independently) in two orders of dinosaurs, and this is probably all the >explanation I need. This is indeed the case. But the question still exists. Why did the ancestors of the dinosaurs develope bipedalism and the ancestors of the placental mammals go for walking on thier toes! I believe that the principle of "preadaptation" is important here. That is a transitional form must itself be advantageous to the organism. The shift to bipedalism requires a differentiation between the fore and hind limbs. The early archosaurs were large aquatic reptiles similar to modern crocodiles(they are called Proterosuchians or "first crocodiles"). They evolved enlarged hind limbs for power in swimming, thus making the shift to bipedalism simple and straightforward. The primate ancestors of humanity were arboreal forms in which the fore limbs were adapted for brachiating, thus making the shift away from a pure quadrupedal gait. The next step, true bipedalism, was thus made possible. -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ??
adm@cbneb.UUCP (05/19/86)
In response to request for a list of Animals with dependent young that do not hide them in a nest of some sort: whales and porpoises, elephants, cows, bison, deer. Of course, it depends on how dependent is defined, but I believe that for all animals on this list, the young would die if not nursed.