g-rh@cca.CCA.COM (Richard Harter) (01/21/88)
Note: I changed the title from the reproductive advantages of rape to one suiting the contents of this article. My apologies for violating net usage. I also removed soc.men and soc.women from the followup list. In article <1413@sugar.UUCP> peter@sugar.UUCP (Peter da Silva) writes: > >There just aren't that many qualitative differences between humans and other >species... most of the differences are in degree rather than kind. This isn't true. It is true that humans are mammals and retain many of the body plan features of mammals. However humans are quite unusual. They have unique characteristics and others that are very rare. Many differences are so marked that they constitute a difference of kind rather than merely degree. Here is a partial list. (1) Upright posture. There are, and have been many bipeds. However all other bipeds keep the spine at right angles to the body and balance the body over the legs. Humans rotate the spine so that it is vertical over the legs. Some animals can assume the upright posture for limited periods of time, but none are built for it. There are a remarkable number of adjustments that have to be made in the skeleton to do this. Upright posture seems to be the key evolutionary innovation in the hominid line. (2) Lack of estrus. In almost all animals the females have an estrus cycle, i.e. they only copulate at certain specific times. [In some species the estral cycle is weak, but this is rare.] Human sexual behaviour has many unusual features. (3) Long life. Interestingly enough, almost all mammals have the same lifespan -- if you count lifespan in heartbeats. Humans are the notable exception; they live four times longer than they ought to, if they fit the general pattern. (4) Big brains. Humans have much bigger brains (particularly cerebral cortex) for their body weight than any other animal. The difference is so marked as to be a difference in kind rather than one in quantity. (5) Complex non-instinctual social behaviour. Again the difference is so large as to be a difference in kind rather one of quantity. (6) A true opposable thumb. I think that this is unique to humans among vertebrates. The Panda does have an opposable "thumb" which is actually an enlarged wrist bone. (7) An advanced tool user. Other animals do use tools upon occasion. However they lack the structural modifications needed for tool using. Again, a difference in kind. (8) Cursorial hunter adaptations. Not unique, but rare. Cursorial hunters kill game by chasing it until it gives up. Example -- a human being (in good condition) can capture a horse by chasing it until it collapses. The horse can run faster, but the human has more endurance. There are a host of modifications needed for this, effecient sweating is an example. Wolves are cursorial hunters. (9) Premature birth. If humans followed the patterns of other mammals human gestation would take about 18 months. Human infants are born semi-foetal. Much of the development that is completed in the womb in other placental mammals is completed after birth in humans. In particular, brain growth is not completed until well after birth. [This is necessary -- if the head finished development the foetus couldn't get out through the birth canal. As it is, it's a tight squeeze; birth in humans is unusually traumatic.] -- In the fields of Hell where the grass grows high Are the graves of dreams allowed to die. Richard Harter, SMDS Inc.
jnp@calmasd.GE.COM (John Pantone) (01/23/88)
Peter da Silva writes: >There just aren't that many qualitative differences between humans and other >species... most of the differences are in degree rather than kind. Richard Harter responds: > This isn't true. It is true that humans are mammals and retain many of the > body plan features of mammals. However humans are quite unusual. They have > unique characteristics and others that are very rare. Many differences are > so marked that they constitute a difference of kind rather than merely > degree. Here is a partial list. Actually, I think they are both "right". The chemistry, anatomy and even behavior of humans is much more LIKE other mammals than UNLIKE, but there are several notable differences > (1) Upright posture. There are, and have been many bipeds. However > all other bipeds keep the spine at right angles to the body and balance > the body over the legs. Humans rotate the spine so that it is vertical > over the legs. I have usually heard this as rotating the pelvis not the spine - but it is really the same thing - our cranium is unusual also, in that the spinal attachment is more "antero-ventral" than in our close relatives the apes - putting the head "on-top" of the spine rather than "in front" of it. The fact remains, though, that from the navel down we are rather a great deal different than the apes, from the navel up (even head/brain included) we are quite a bit alike. It has been said, in defense of the concept of Neoteny as a major force in the evolution of humans, that an adult human is very close in form to a foetal chimp. > (4) Big brains. Humans have much bigger brains (particularly > cerebral cortex) for their body weight than any other animal. I have always questioned this - chimps gorillas and orangs, as well as most of the cetaceans (sp?) all have complex cerebral cortexes (corti?). Although the baleen whales can't compare in brain/body-weight to humans - their brains are hugely larger than ours - and their body form is so radically different from ours that a body weight comparison seems awfully weak. I think our brains are actually less "different" than we think. (Except perhaps in function - but not in form). > (5) Complex non-instinctual social behaviour. Again the difference > is so large as to be a difference in kind rather one of quantity. I disagree - many animals have complex social behavior - monkees, canines, etc. I think that our actual behaviour is really a difference in quantity not kind. > (6) A true opposable thumb. I think that this is unique to humans > among vertebrates. The Panda does have an opposable "thumb" which is > actually an enlarged wrist bone. What makes it "true"? Chimps (especially the pygmy chimp) have a very well opposable thumb. Much, Much better than the Panda's (great, not red). Koala "bears" have 2 opposable thumbs (at least on their forelegs/arms). Check out your "opposable" thumb - it really doesn't truely oppose any finger, except perhaps the little finger - it is "off center" of all the others. > (7) An advanced tool user. Other animals do use tools upon occasion. > However they lack the structural modifications needed for tool using. > Again, a difference in kind. This one puzzles me - what structural modifications? (opposable thumb? - see above). > > (8) Cursorial hunter adaptations. Not unique, but rare. Cursorial > hunters kill game by chasing it until it gives up. Not unique - true, also not rare. Virtually all canines use this means of hunting - in fact it has been suggested that the fundamental reason for the human/canine association is the sharing of this (and pack) behavior. Wolves, wild dogs, cyotes - all Cursorial hunters, none - even today - rare. All in all - I am still more likely to say that we are far more like other animals than we are different. -- These opinions are solely mine and in no way reflect those of my employer. John M. Pantone @ GE/Calma R&D, 9805 Scranton Rd., San Diego, CA 92121 ...{ucbvax|decvax}!sdcsvax!calmasd!jnp jnp@calmasd.GE.COM GEnie: J.PANTONE
rob@amadeus.UUCP (01/24/88)
>Peter da Silva writes: >> >>There just aren't that many qualitative differences between humans and other >>species... most of the differences are in degree rather than kind. > Richard Harter writes: >This isn't true. It is true that humans are mammals and retain many of the >body plan features of mammals. However humans are quite unusual. They have >unique characteristics and others that are very rare. Many differences are >so marked that they constitute a difference of kind rather than merely >degree. Here is a partial list. > >(5) Complex non-instinctual social behaviour. Again the difference >is so large as to be a difference in kind rather one of quantity. It seems to me that some of the traits you have listed will apply to the great apes too, especially this one. Perhaps the behavior is not as complex (although I'd doubt it) but chimps and gorillas have to learn how to do such necessary functions as mating and raising offspring. These behaviors are not instinctive any more than they are for humans. --- Dan Tilque This is a borrowed account, so be sure to indicate that replies are for me and not for Rob. ... ...