First of all, Snowbaby, you showed alot of class in that last post of yours. Apology more than accepted!
I wanted to address your point about animal mothers leaving their babies to go search for food (I'm afraid I'm a true biology geek and couldn't pass this one by)...
Mammalian mothers can be divided into two groups: those who have "support" from a mate or members of their social group, and those who don't have mates and are solitary creatures. The physiology of these two groups is quite distinct. For one thing, the composition of the mother's milk is different: the "isolation" moms have a significantly higher fat content, allowing their young to go without nursing for longer periods of time. Their young also behave differently. They do NOT emit distress calls when mother is absent (which would obviously attract predators). These are just two of the major ones, but there are other differences as well (like body temperature regulation, for example).
We know that humans, and all primates, do not fall into this category. Not only because we are social animals (meaning there is always someone around to hold a baby), but also because our milk composition matches those of mammalian mothers who do NOT leave their babies' sides. Low fat, frequent nursings, near-continuous physical contact with adults...the young do NOT like to be out-of-arms, and will emit distress cries if they find themselves so abandoned (under the evolutionary expectation that if someone is not holding them, they are at risk, and that if someone is around, a distress cry will provoke an innate instinctual response - even in female group members other than the mother, adolescents included - to pick up the infant).
Now, while I think it's very accurate to say that it is UNNATURAL for a baby to sleep in isolation, I do know from years of research that biovariablity is a substantial consideration. Not all creatures are the same, and that certainly applies to behaviour. I'm not sure it is fair to assume that a baby who sleeps happily in a crib still "needs" his mother by his side. And I certainly have no objection to parents who feel better with baby in a crib, if baby is happy there. While I honestly believe that most babies don't like cribs (evident in the supposed 33% rate of "sleep disorders" in North American babies that is virtually non-existent in other cultures; not to mention the host of sleep training manuals available to parents), I'm quite willing to accept that there are babies out there who sleep better with a bit of space, and/or are quite accepting of a crib.
I asked the question about what makes a mom unable to cosleep, and I think we've gotten some good answers. Using Graceoc as an example...obviously she has never had an easy time with sleep, and I don't think it's at all unreasonable that she doesn't enjoy cosleeping. I also feel it's apparent from her posts that she would not force her child to a crib, but rather is grateful that her child took to the crib. Someone else mentioned they had a susceptibility to depression, which is most certainly triggered by sleep deprivation, and that too makes perfect sense to me. I guess my point is, that perhaps those who don't cosleep are understandable exceptions to the general expectation that cosleeping would/should come naturally to all mothers.
I also agree with whoever suggested that the babies may be picking up on the mother's anxiety. I do find it hard to understand how a newborn would have troubles sleeping next to mama, but if the mother herself has anxiety or sleep issues then it makes perfect sense. Not only are babies sensitive to mood, but let's remember that the mother guides the infant in their sleep cycles, breathing, and heart rate. If the mother is having her own sleep issues, chances are her baby is not going to be cycling through the normal sleep cycle. So I can see how this ends up being a vicious circle in which nobody is sleeping well.
Snowbaby: I just wanted to mention that ITA with you about cats being "non-disposable"...but also wanted to reassure you that your cats will almost certainly stay away from your newborn. My cat had always slept with me, but when DD came along she wanted nothing to do with that noisy, unpredictable creature. Besides, I'm always aware of where the cat is, just as I'm always aware of where baby is. So don't let the cat issue scare you.
And...I have to respectfully disagree that the jury is out on safety of cosleeping. I've reviewed the data very carefully on both sides and the evidence for the preferred safety of a crib is weak, and based on very shoddy science in most cases (I'm a research scientist and quite skilled at critically reviewing data, so I'm not just saying this out of bias
). The biological evidence accumulated by such researchers as Dr. James McKenna (visit his sleep lab here
) is pretty compelling, especially in the context of evolutionary behaviour and anthropology. Mammalian babies simply were not designed to sleep in isolation, so it makes sense that there are adaptative behaviours that surround cosleeping, such as the above mentioned fact that mothers regulate their babies brain waves, sleep cycles, respiration, heart rate, and body temperature. That mothers' own sleep cycles change in response to cosleeping, avoiding the deeper (less "aware") stages of sleep, while still engaging in restorative REM sleep. I think SIDS is a natural consequence of a neurologically-underdeveloped infant (which human babies are: the most immature of any primate at birth due to large brain size competing with the limited pelvic girth of a bipedal creature) being deprived of the stimulus of an adult nearby. It's actually surprising to me that the rate of SIDS isn't higher than it is, but again that probably speaks to biovariability and the adaptive nature of humans.
Okay, I'll shut up now...