A really great question (sort of)

A guy on the Survivalist Board put up a post about rebuilding society with 30 people.  Now personally, I think he and several other people overcomplicated the situation.  Here is my response (including details on what I would do and how)

A group of 30 could survive ASSUMING a survival expert in the group that actually knows what they are doing AND DOESN'T FRIGGEN VIOLATE THE RULES.

I put that last part in all caps for a reason. The show on Discovery, "Naked and Afraid" puts two people supposed to be primitive survival experts into actual primitive survival situations. However with a couple of exceptions these people violate the rules and it ends up screwing them. So, I'm going to list out how a group of 30 people survive in a situation where their only resources are the clothes they are wearing.

First, the one primitive survival expert is ultimate authority PERIOD. Anyone not doing what the leader says is punished severely and instantly. Three times of disobeying the leader results in banishment if not death on the spot. The first person to disobey needs to be made a very brutal example of to prevent it happening again, ditto with the first person to reach 3 times disobeying. However if the first person to disobey (or two) are punished harshly enough then probably it won't happen again after that. A small group of just 30 and people get the message pretty quick.

Important rule ... NO ONE is allowed to evacuate bowels less than 300 feet from where ever the group intends to sleep, and said evacuation is a location decided upon by the leader (more on why later) and a hole must be dug at least one foot deep and then covered.

1) Fire. 
Leader starts a fire IMMEDIATELY. Even if where they are isn't a good location for the group to pick as a "camp" a fire can be moved (any decent primitive expert should know how). In every survival show I've seen this is always the #1 mistake I see made. Start the fire soon. 

Once the group is where they are going to make camp, for the love of all that's good and holy make it BIG. Cooking occurs on the outer edges not the middle. A fire that's 10 feet in diameter will keep away predators, generate smoke to keep away insects, keep up morale when things start to suck (and in the beginning they will), generate heat, and in the beginning give a way of treating water. 

2 people are tasked with tending the fire, three more are tasked to obtaining fuel for it. (in the beginning this will mean finding stuff on the ground and even tearing branches off trees ... smoke is actually a good thing to ward off insects so some "green wood" is very desirable. Not only that, but sometimes just walking to the nearest tree and tearing thins off it is easier. Energy conservation is important at this stage.

2) Water. 
EVERYONE ELSE works on getting a flow of treated water established. Water from the ground must be boiled ... PERIOD. Yes I know there are some exceptions but with 30 people generating enough water is going to require obtaining water from "untrusted" sources ... that means boiling. 

Until there is a good "flow" of boiled drinkable water NOTHING ELSE matters. EVERYONE (except fire tender-ers and fuel gatherers) is put to getting this done. 

Once it is done, probably 6 people will be put to keeping that flow of water (transporting water from the source to the fire and boiling, and adding to the number of drinking vessels). 

Another huge mistake that I see being made by supposed "experts" is risking drinking running water from a stream. Any water that comes off the ground, out of the ground, and so on MUST be assumed to be bad and MUST be boiled. Water out of a plant doesn't have this rule but getting enough water for 30 people from plant sources is nearly impossible. You WILL need "ground water" from a steam or digging a well or evaporating sea water (not easy given zero resources). I can't stress this enough. Water from the ground must always be assumed bad and therefore it must be boiled. There are exceptions but you'd better be VERY confident in that exception. The entire group of 30 can be killed off quite quickly from drinking just a small amount of bad water. If not from the actual illness from the water itself, then because the illness has made the group too weak to obtain food. Boiling water doesn't take that long, it's why fire is the first item ... it's the first item exactly because the REAL most important thing is clean water.

3) Shelter. (notice it isn't food yet) 

Leader would need to ensure that the components for enough shelters are created and built. All structures for 30 people would have final assembly done at once. This eliminates the arguments over who gets to sleep in the first constructed shelters. The 19 people not working on the fire or water are all working on this task. Done properly, within about 4 or 5 days the group has a very large fire, plenty of water to drink, and shelters from the elements. Many small shelters are better than one large shelter (they hold together better in heavy winds).

4) Food. 

Branches are torn off trees and FILED (no tools yet) to points on rocks. Again, all 19 people not on fire or water duty are put to acquisition of food. 

Most predators are likely going to be drawn to the area the group is using for bowel evacuation. 19 people, properly lead, should be able to relatively safely kill a predator (boar or cat). 

If the main predator is snakes and "lizards" (crocs or aligators) then you do have to go get them but they are the "safest" to get assuming the leader knows how (crocs and aligators are safer ... snakes are too much work for the amount of food unless one is at hand). If the main predator is bear, that means fish ... DO NOT tangle with bear even (especially even) babies. Baby bears are given VERY wide space. A full grown bear will often not bother with humans at all ... except mothers who will violently protect their babies. 

The leader, besides getting sharpened branches to the group also teaches people how to weave nets and create baskets, both of which are used for trapping fish, small game, and birds. In the early stages, these are pretty much always the primary source of food. 

Again, snakes, kill them if they are close, but often snakes require a large expenditure of effort for the amount of food obtained so they shouldn't be "hunted". Fishing with nets, trapping fish/sea life with the baskets, trapping small game/birds with nets and baskets. In short, you need a lot of nets and a lot of baskets to feed 30 people. Again, all 19 people should be put to doing nothing but this for probably 2 or 3 days. 

THIS WILL BE HARD. People will be hungry and will want to go off hunting with the first weapon. It's one thing to set a trap with the first net/basket. Especially fish traps. Set them as you go. Hunting should be done only in small groups with the leader while others are still working on baskets. Again, far less energy is expended in trapping/netting than in hunting which is why the early effort should be on baskets and nets NOT on hunting.

The nets need to be fairly large and "closely knit" (meaning small holes) and that takes time. In the right regions with boar and cat predators, these can be obtained by a few people (from the bowel evacuation area) to keep everyone going at first. Someone with decent primitive survival skill will know how to gut an animal with nothing more than a pointed stick. However without knives a lot of meat against the skin will be lost. Bones are OVERWHELMINGLY the best place to start with the creation of sharp tools however and bones from predatory animals are the best place to start as they tend to be very dense. From here, the 3 best people with the fishing and 2 best hunters are put to doing that now that there are sharp tools. They will also "treat" their kills/captures (gutting/skinning), The two people that tend the fire will do the cooking for everyone. Two people will at this point be put to gathering edible plants. At this stage calories from protein and animal/fish fats are going to be the most important. which is why the gathering doesn't occur till after protein sources have been found.

5) Improvement. 

At this point there is a VERY good sized fire, plenty of water to drink (actually well more than that for soups, cleaning, and so on), only mediocre shelter, and enough food to prevent starvation. Bones are now giving the group tools to make fuel for the fire easier, the creation of more nets and baskets much faster and easier, and the acquisition of predators for meat easier. 12 people are now without "jobs". They will be put to the task of improving the shelters (ideally permanent "hard" structures made of brick), running water, "harder" tools (stone axes) and generally attempting to improve life. A good sized C shaped wall should be built around the camp to keep out predators and snakes. (after 5 to 10 years the wall can be pulled down as predators learn to avoid the humans with the pointy sticks ... however whether or not the wall is pulled down is going to be a factor of the primary weather. That C shaped wall can keep away a lot of wind if there are frequent storms (tropical or blizzard) which can make it easier to keep structures standing.

Hopefully the leader understands something about building vertical aquaponics systems. These generate a lot of fish, vegetables/berries/herbs, and don't require much effort so some people will be put to that. "Horizontal" gardens/farms require too much work for a group of only 30 and should be avoided.

Any "prey" animals will need to be captured so that domestication can begin. It's about having food sources brought to you so that energy doesn't have to be expended on capture/hunting on an ongoing basis. "animal husbandry" of wild animals can be a little tricky if the animals are penned too tightly. It's best if you can have a fairly good sized area where the animals are mostly penned by the land and there is a fairly good sized space. Shelters will be needed to be built for the animals as well AND they will need to be guarded against predators which means another shelter for the "shepherd on duty"

6) Moving forward. 

In a group of 30 there will be pregnancies so any natural medicinals will need to be found, determined, and ideally made part of aquaponics as well or if it's a tree then locations identified. Hopefully someone in the group has some kind of understanding of midwifery.

THAT IS SERIOUSLY ALL THAT IS NEEDED for probably 20 or more years. The group is going to be too small to worry about larger "societal" things like law enforcement and judiciary and accountants. In the beginning the society would need to be very "communal" in that everyone works and everyone has what they need (water, shelter, food). It will be at the leader's sole discretion to determine if someone isn't pulling their weight and if they aren't ... they are gone.

Only 20 plus years into it will something more robust be needed and then likely it will evolve into a tribal system. The "elders" will take over the leadership of what will become a tribe.

Whether or not there is any expansion beyond a basic tribal structure is going to depend on the natural resources, competition with any other groups/tribes, and other things.

HOWEVER, for a very long time, the 30 people can make it. ASSUMING there is an actual primitive survival expert in the group that doesn't violate the rules trying to get from one place to another (not building a fire soon enough) or trying to build shelters for comfort before a stable supply of drinkable water is established. Shelter is not needed to keep safe from predators if a large enough fire is built. Not even boars will get too close to a large roaring fire.

If the group is without someone with primitive survival training AND expertise ... then that group is probably really screwed and not likely to make it a month or at most two.


BASIC LONG TERM PRIMITIVE SURVIVAL RULES

1. FIRE FIRST. In any survival situation, build a fire as soon as possible. No kidding.  Like right away.  You can keep a fire going, you can travel with a fire.  So if you aren't at a good camping location, build a fire right away and just move with it.  Then, when you are at your Bug Out Location (BOL) you can make a larger fire.
2. WATER.  Water must be boiled before being drank.  You need to be thinking of water by the end of your first day in a survival situation.  By the end of your second, your fire should be used to boil water which you then drink.  In other words, if you are travelling, then you travel for one day, then do nothing but acquire water the second day.
3. SHELTER. Shelter makes it easy to survive if the weather turns ugly ... and it's only a matter of time before it does, and it will probably happen sooner than you like.
4. FOOD. Trying to kill "prey" animals like deer or rabbit isn't very easy.  Instead think trapping/snaring of fish and small game.  It's generally a much better "yield" for the energy you expend.  Doing this means nets and baskets for trapping (and if you're by an ocean, trapping fish is an instant "go to")

Everything else from here starts to get much easier.  

However, in any survival situation, get a fire going and think about water RIGHT AWAY.  Then shelter, then food.

If you acquire good skills in each of those areas for "primitive survival" you can pretty much survive anywhere.  Learn how to create a "bow drill" to start a fire.  boiling water is fairly self-explanatory if you have a good fire going (just don't let it go out!).  Shelter requires knowing how to use vines or other materials as lashings for larger things and knowing how to create some sort of roof against rain.  Trapping/snaring requires knowing how to use natural materials to create nets and baskets.

ALL of these skills are actually very easy to obtain and are not hard to do.

If you can't do every one of these things yourself then it should be a pretty high priority to acquire those skills.  In a true SHTF scenario you may not be able to get to your BOL or it may be destroyed.  Any prepper MUST know how to survive with few resources.