The human race. The peak of natural evolution on earth. Of all species ever to evolve on the earth, humans have the highest survival rate of them all. Not only can they adapt and react to their environment, they can make their environment adapt and react to them. And that, more than anything else, is the unique way humans became the ultimate survivors.

However, humans have been evolutionarily dim over much of their existence. As they worked harder and learned more and were able to affect their environment more fully, they changed that environment, and not always to the better. The Matrix Smiths called them a virus. And though, specially, humans are most definitely mammals, and not a virus (duh), they do sort of act like one.

Disease is one thing humans fight in order to survive. Either their immune system combats the disease, the medicines weaken the disease, or they're cooked. And they know this. So they always fight to learn more about disease, develop better treatments and preventative measures against disease. Eventually, if I take an optimistic standpoint, humans may even cure old age.

I would predict that, if this were to actually occur, there would come a point in a person's life where they will be given a choice. Let's say, for the sake of argument, that this happens when a person turns 25. Old enough to look mature, old enough to know a little bit about life and the human condition, but not old enough to look old or tire of living. Normally, anyway.

With population an ever-present concern, limits would have to be placed on further growth in order to reduce current population to a number more sustainable in our situation. This entire subject is very complex. So it wouldn't be very smart to allow everyone to live forever, but keep their ability to produce children at the current rates. That just would not be sustainable. So the choice would have to be an equally complex one, and will probably fluctuate over the years.

Let's say, for example, we arrived at the cure for old age right this very instant. Most of us can pretty much agree that the earth is way overpopulated. So giving a vaccine against old age to the entire earth's population would be incredibly stupid. Giving it to only those rich enough to buy it would be both unfair and also stupid, as it would eventually reduce the gene pool and doom our species as well. A random pick of who gets the treatment wouldn't satisfy anyone, either. So, the first step to determining what choice to give people would be to gather the following statistics:

1.) What percent of the earth's population wants to live forever?

2.) What percent of the earth's population wants to have children?

3.) What percent of the current population is ideally sustainable?

For the sake of example, let's say that 60% of the earth's population wants to live forever, 50% of the population wants to have children, and 40% of the current population is ideally sustainable. That means the population would need to be reduced by 60% to reach ideal sustainability.

Now, there is no need to drop the population immediately. So, let's say that 50% chose immortality and 40% chose children, with 10% unable to decide and postponing the decision another 5 years.

Next thing to do would be to decide how many biological children a person can have in order to have a steady population decline unto the ideal sustainability levels. Since 40% of the population chose children over immortality, by limiting one biological child to each person there is the potential of up to a 20% population decrease in only a single generation.

Let's say that in the next generation, who are equitable to 20% of the population (since most of the previous generation, their parents, should still live), 15% choose immortality and 5% choose children. That could potentially award a 2.5% population decrease within the second generation.

So it would keep going along like that, until the ideal sustainability population is reached. At which point reducing overall population size would no longer be the ideal. Sustaining it will be. So the maximum number of biological children each person who chooses children can have over the further generations would fluctuate according to how many people chose immortality and how many children were actually born.

That limit would skyrocket to almost no limit if/when we were to actually move out into space. The more space we have to live in, the more resources we have available to our survival, the bigger our overall population can be and still be in the ideal sustainability percentile.

There would probably be some kind of universal governmental body (both a part of and separate from existing governments) that would oversee this kind of thing. They would probably all be scientists, the best to know the statistics and what to do with them and how to calculate what needs to be calculated.

For example. Let's take the Sahara vs South Carolina. The Sahara is a desert. It has a few oasis, but for the most part is sand. The available space is plentiful, but resources are few. South Carolina is a coastal state. It is rich in resources, but nowhere near as large in space as the Sahara is. Yet, it would be able to support a larger population than the Sahara, due to available resources.

The people in charge of these decisions would need to know this. They would need to be able to limit the population growth in the Sahara much more than in South Carolina.

Each area would probably have its own team looking out for it. They would be in charge of keeping the population within that area in the ideal zone. With people moving from area to area, people adopting kids, etc, it can get very complicated and difficult to sort it all out. Which is why each team would be in charge of a small relative area, rather than one team in charge of the whole planet.

Furthermore, if someone who has never had a biological child should be found to be incapable of having any children, they should automatically be given the right to the vaccine, though they could still waive that right if they so wish.

At least, this is my view of how things should go should we invent an immortality vaccine. Dangers are high, complexity is huge, and we've screwed our planet over so many ways to Sunday that we can't cure all the problems over night. But reducing overall population growth over the span of generations is a good place to start. Inventing immortality is an even better place to start. I know I'd choose it.