I don't see how it's relevant...
On Jul 21, 2:18 pm, rigsy03 <[email protected]> wrote: > You have forgotten child-bed fever- I forget the medical term which > infected and killed new mothers. It was linked to unsanitary > conditions that entered her body after delivery. I think the term > begins with a "p"- my toaster brain will think of it later! :-) > > On Jul 21, 4:10 am, GarrieMushet <[email protected]> wrote: > > > > > I didn't say that EVERY woman has trouble, and that EVERY birth canal > > is unable to cope with the dimensions of a baby. > > > I said that the percentage of women who have trouble has increased > > greatly in comparison with our ancestors, and a large majority of this > > is due to the increase in the size of the brain (and therefore, the > > head). > > > Consider what it was like 250,000 years ago, when our brain was around > > 450 cubic centimetres at adult size. Smaller brains and smaller heads > > meant smaller weights of babies. So the likelihood of a baby being > > over 14 pounds 250,000 years ago was minimal. Today, there are a > > higher number of instances of babies being born well over this weight. > > It's not a majority, no. But it's a larger percentage than it was > > before the increase in brain size. > > > Also, you are correct that baby's bones are soft and pliable. But you > > cannot compress and expand the brain to get it out of the womb without > > seriously damaging the baby in the same way you can do with it's > > shoulders and limbs. In order for the baby to survive, the birth canal > > needs to be able to pass quite a large head without ever squeezing it > > hard enough to cause damage, and with soft cranial bones, that isn't > > very hard at all. > > > And I should make the point that the initial rate of births of mothers > > and children during childbirth was quite high, but it dropped > > considerably, because the birth canal itself would have evolved to > > have been more accommodating of the dimensions of a baby at the time. > > Had the human species been left to its devices for a few more > > thousands years, I don't doubt that our current rates of mother/child > > death in childbirth would be even lower than they are. But as with > > back pain, we have created an environment in which mothers and > > children are aided by artificial means to overcome any physiological > > shortfalls from which we still suffer, and so any problems that are > > still inherent are unlikely to disappear from the species any time > > soon. > > > On Jul 21, 3:22 am, rigsy03 <[email protected]> wrote: > > > > The birth canal can handle 14 pound infants whose bones are still soft > > > therefore I disagree with you. > > > > On Jul 20, 1:42 pm, GarrieMushet <[email protected]> wrote: > > > > > Jim, > > > > > Yes, 1,400 cubic centimetres is the average volume a fully adult human > > > > brain. I should have made this distinction. > > > > > However, human beings have larger brains than their ancestors did at > > > > all stages in life. So which an infant's brain isn't quite 1,400 cubic > > > > centimetres, it is still a hell of a lot larger than those of our > > > > ancestors at the time of birth. > > > > > The baby's head is usually the widest part of its body at the time of > > > > birth. You are right to propose that the shoulders would also cause > > > > considerable difficulties, but it may be interesting to note that one > > > > of the physiological changes that would be necessary to accommodate a > > > > larger head, heavier head (which is necessary to accommodate a larger, > > > > heavier brain), is wider shoulders. > > > > > Regards, > > > > > Garrie > > > > On Jul 20, 5:57 pm, retiredjim34 <[email protected]> wrote: > > > > > > Garrie - again, many thanks for your thoughtful, thorough reply and > > > > > observations. > > > > > I think the only one I would question is the brain size - I > > > > > believe you are citing the size of the adult brain. An infant's brain > > > > > size is much smaller. So delivery of the infant at birth might not be > > > > > nearly the problem you think. Also, at birth is the head the largest > > > > > object, or is it the shoulders or the hips? > > > > > You are quite right about natural selection preferring nothing - > > > > > it has no preference. It just describes the result of a natural > > > > > process, as you point out. Jim > > > > > > On Jul 19, 12:52 pm, GarrieMushet <[email protected]> wrote: > > > > > > > Jim, > > > > > > > In evolutionary terms, the most important goal is to hand down your > > > > > > genes. The prerequisites to this goal are reproduction and survival. > > > > > > Therefore, there is NOTHING more important than survival in > > > > > > evolutionary terms. > > > > > > > So no, I wouldn't say that sleep serves a purpose more important > > > > > > than > > > > > > survival. I would say that sleep serves the purpose of survival, in > > > > > > fact. > > > > > > > You are entirely right that sleep makes the sleeper vulnerable to > > > > > > prey > > > > > > that is not asleep. But natural selection does not know this. > > > > > > > Many people see evolution and natural selection as independent > > > > > > conscious agents who constantly and actively refine the organism to > > > > > > make it better and better at surviving. This just isn't the case. > > > > > > Natural selection and evolution aren't 'aware' of anything. They do > > > > > > not know that sleeps makes up vulnerable. I daresay that if > > > > > > evolution > > > > > > and natural selection were conscious creative agents, then sleep > > > > > > would > > > > > > have been abolished long ago. > > > > > > > It hasn't though. Why? This is your question, I believe. Why haven't > > > > > > we evolved to not require sleep, when in fact, it is a danger to the > > > > > > organism to be a sleep. > > > > > > > Well first of all, let me say that sleep is not the only phenomenon > > > > > > of > > > > > > living creatures which would seem to be a disadvantage to individual > > > > > > survival. Let me introduce to you a few of them within our own > > > > > > species: > > > > > > > 1) The human brain. > > > > > > > Around 2 to 2.5 million years ago, our ancestors had brains with a > > > > > > volume of only 400 cubic centimetres. Around that period, it bloomed > > > > > > to about 650 cubic centimetres. Around 500,000 years ago, it jumped > > > > > > to > > > > > > 1,200 cubic centimetres. And then around 150,000 to 200,000 years > > > > > > ago, > > > > > > when the first 'homo sapiens' walked the plains of africa, it jumped > > > > > > to its current volume of around 1,400 cubic centimetres. > > > > > > > But the problems that came from the increase in the volume of the > > > > > > brain were quite substantial. For starts, millions upon millions of > > > > > > women have died in the last 200,000 years because their pelvises > > > > > > have > > > > > > been unable to pass the head of a baby needed to house this massive > > > > > > organ. Quite a lot of the time, the baby perished too. > > > > > > > Not only that, but the brain takes up one fifth of the entire human > > > > > > energy reserve. So 200,000 years ago, our ancestors found themselves > > > > > > having to hunt and eat a lot more food than they had to when their > > > > > > brains were only 400 cubic centimetres. > > > > > > > Our heads are now so heavy that the risk of a human suffering from a > > > > > > broken neck is massive compared to that of our chimpanzee cousins. > > > > > > > 2) Walking on 2 legs. > > > > > > > Humans still haven't adapted to walking to 2 legs as fully as they > > > > > > could be. Walking on two legs is a relatively recent practice among > > > > > > the species, and as such, we haven't quite had the chance to > > > > > > assimilate to it. The statistics for the number of humans with > > > > > > chronic > > > > > > back problems are enough to convey this, and almost every single > > > > > > human > > > > > > will have personal experience of it at one point in their lives. > > > > > > Going > > > > > > back 200,000 years, the notion of back trouble was even more > > > > > > daunting > > > > > > than it is today. For us it means annoyance when rising from our > > > > > > chairs, but for our ancestors it was the difference between escaping > > > > > > predators and being gored to death. It was the difference between > > > > > > catching the extra prey necessary to provide the energy that our > > > > > > brains required and lying on the african plains, dying from > > > > > > starvation. It was the difference between between being sexually > > > > > > attractive and sexually selected, and being cast aside to die > > > > > > without > > > > > > ever passing on their genetic codes. > > > > > > > So why oh why has natural selection not ridded us of these burdens? > > > > > > > Well, because Natural Selection really doesn't care. Natural > > > > > > selection > > > > > > is indifferent to what makes us vulnerable. Natural selection has no > > > > > > inclination to remove the characteristics which cause us great pain > > > > > > and discomfort. Natural selection doesn't care if we live or die. > > > > > > Because natural selection isn't capable of caring, or thinking, or > > > > > > realising what characteristics are beneficial, and which are > > > > > > burdensome. > > > > > > > The reason we continue to sleep, walk on 2 legs, and have massive > > > > > > brains is the NET effect they have on us, as a species, is a > > > > > > beneficial one. So although, if you look at sleep from one angle, it > > > > > > seems to be a great disadvantage, if you look at it from another > > > > > > angle, you see that the benefits we gain from it far outweigh the > > > > > > disadvantages. > > > > > > > Afterall, sleeping for 8 hours a day only makes us vulnerably for 1 > > > > > > third of our lives, but it keeps us fresh and awake and able to > > > > > > escape > > > > > > predators and catch prey for 2 thirds of our lives. If we never > > > > > > slept, > > > > > > the nature of our physiology would make us vulnerable for 100% of > > > > > > our > > > > > > lives (and short lives they would be!). > > > > > > > In conclusion: > > > > > > > Yes, many organisms have died from being asleep at the wrong time, > > > > > > having massive brains, and > > ... > > read more » --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups ""Minds Eye"" group. 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