awe this subject could fire a wonderfully heated discussion
lets take it one step deeper to the first female human in constant estrus being able to choose and Denny mates at will and produce maximum amount of offspring. where as only the males best at providing would be chosen as mates there by providing the origin of our extremely competitive nature which has truly separated us from the rest of animal kind

Evolution works by single mutations occuring in DNA every time it replicates.  Sometimes the mutation provides an advantage, such as bigger teeth, something like that, sometimes it's a disadvantage, such as a smaller brain, and sometimes it happens to "junk" DNA.  If there is an advantage, then the organism will be able to compete better for resources than other organisms, and so will survive, hopefully to pass on it's better advanced genes to the next generation.
  That used to be the case.  Now, unfortunately, it seems like someone shat in the gene pool, and we have everyone surviving.  If someone was born without the ability to have babies, then surely it is not advantageous for that person to have babies because then they will, in turn, not be able to have babies and thus the distinct disadvantage continues.  Also, because of advances in medicines, fat people, stupid people, and so on are surviving to pass on their stupid, fat genes.  Everyone is surviving.  People say this is a good thing, but is it?

You know, surprisingly, your life would not be too difficult, for a number of reasons.  You wouldn't have anything to compare it to, so you'd think that your life was just great.  Secondly, weather, wild animals, food problems are also modern problems.  Perhaps not in the same way, but you would be much more used to being around bears and snakes, and only extreme conditions would really endanger you, just as it is today.

But, if you didn't know those things, such as anaesthetics, existed, you would have absolutely no problem with having operations done on you without them.  Also, it is possible to make soothing medicines and remedies from wild plants.  Where do you think modern medicines come from?
  Also, you say "without warm clothes."  Of course people had warm clothes in the stone age, as far back as you can go, really.  Tribes people the world over do not go around naked or wearing bark loincloths only, you know.  They would kill bears, deer, and other fur bearing animals.  Fire, also, is something you mention as absent, although I do believe controlled use of fire goes back 1.5 million years ago.
  And the point is, if you couldn't cope with giving birth with no medicines, or couldn't stand amputation of an arm to prevent infection and death without anaesthesia, then you would die, and your genes would not pass on, and this would be, from the point of view of evolution, a good thing.

The last time I experienced great pain was when my right calf muscle was opened up by a sheared off piece of metal from a table about two years ago.  I have a big, enduring scar there.  Before that, my nose was smashed by someone headbutting me in the head.
  Plants can be used for medicine totally wild.  Salix sp, digitalis sp, both of these are very strong (very very strong) pain killers, and salix (willow) is very common.  There are many many others.  Too many to know fully.
  The point is, though, that hunter gatherer life is actually very leisured and relaxed.  Obviously if there is an accident, you might die quite quickly, but you would make sure that you never had an accident.  Simple as that.  All hunter gatherer peoples move from one food source to another in a relaxed manner, waking up when they please.  These people do not suffer heart attacks from work related stress - something that regularly happens in London, New York, Tokyo, Frankfurt.  People would learn about pain early on and would become accustomed to it.  The only major problem would likely be infection of small wounds - and that can be avoided by repeatedly washing the wound, something that requires common sense rather than a computer and a team of scientists to realise.

Clearly you need to learn some primitive skills.  If a hunter doesn't know any plants that can help him, then he is not worthy of hunting.
  If an hunter can't find dry wood, or is not prepared, then he is not any kind of woodsman I know.

  The stabbing scenario..... Well, obviously you wouldn't know about modern medicine, but of course you would want a way out of the situation if you had been stabbed.  I know of no spear that can make a hole that big, but assuming it can, you can find some plantains leaves to soothe the pain, and maggots to eat the dead flesh.  You can use a flint or obsidian knife to amputate your leg, or you could clean it out and hope for the best.
  In winter there is actually plenty of game.  Many animals are, of course, hibernating.  But many kinds of edible prey are around, although actually going out and hunting them if often not viable in winter.  That is why you use knowledge of traps to help you, simple deadfalls, snares, and so on.  That's the winter way.
  It would also be rare to hunt alone, and if you did, you would be totally prepared and know what to do in most situations.  Also, true hunter gatherer groups rarely fought each other.  Farming brought about warfare (eg, in the Great Basin in America, and most of Australia, warfare was incredibly rare if it happened at all.  In the northeast USA, where there was much agriculture, there was also a great deal of warfare.)
  The point is, if you can't hack it, then you die.  That is natural selection.  People can't understand it nowadays, they would be far too scared.  But it's the natural way.  Any other is just wrong.

ok.
These "scenarios" kind of ideas, they dont make any sense. It is like the very idea of a natural athletic woodsman getting into a scrape that only a city slicker would even think about ( because they are so ignorant) If you have lived in the wilderness all of your life (about twenty five years) and you experienced, learned, and know much of what there is necessary to know, then nothing will surprise you. You will likely get into a scrape
because you are dumb, there you go, you dont pass on your genes so more dumb peopel are made.
This is evolution.