Ice cream girl + doomsday prediction

Today is wednesday, 21st of september 2016. My 3rd last day of work. I went and got icecream after i had lunch at the loving hut. The icecream girl looked very happy to see me. I regularly got icecream at that same place, cafe gelato, after lunch during lunch break at work. I get the coffee in a cup, single scoop. Coffee to wake me up from my after lunch sleeinesss, single scoop because too many carbs overworks the body, and cup so i can eat it with a spooon.

I just had another idea. The doomsday argument. There have been ~ 100 billion humans that have lived on earth so far, so if the total number of humans to ever live was 200 billion, then there would be a 50% chance that any particular human is born in the first 100 billion people. However, if the total number of humans to ever live is much larger, say 100 trillion, then there is a tiny chance that any human born would be in the first 100 billion. I have to queries with this argument. Firstly, there was never really a first human to be born... humans gradually evolved from other organisms over millions of years. So should we count the total number of living things instead? That number would be insanely big, and we have no way of accurately estimating it, to my knowledge. But i guess you could just draw the line somewhere and say "this is the first human", then the doomsday argument still makes sense. However by that logic, you could then define any group (of people) in the same way... Take the total number of cars ever made, see where your car ranks, and get an idea of how likely it is that you are driving the first of so many cars.  My second query; What if at some stage humans discover how to live forever, then the world reaches the maximum number of people it can feed, so people have to stop reproducing... nobody knew is born. In terms of the doomsday argument, this would be the equivalent of an extinction. However, new people will still be born due to death by accidents, murders, and disease. The estimated maximum sustainable population is estimated to be about 11 billion. The UN estimates it'll reach this around 2050-2070, let this be MP. In 2050 I'll turn 61 years old. Today, there are ~130 million births per year, so by 2050, ~4.4 billion more people will have existed, adding to the 100 billion that have existed already. Let the year that aging is cured be TI. It is assumed that TI is after the world population maxes out. Between MP and TI, new people will be born at the rate that they die. Today, ~0.7% of the world population dies each year. At 11 billion, this will be ~77 million deaths per year, therefore 77 million births per year. in 2001, there were 31 million preventable deaths. That was 0.5% of the population. If this percentage was the same after TI, then there would be 55 million new people per year after TI. However this percentage is expected to decrease as civilization improves. I can find the trend that it is decreasing, and extrapolate to 0%, to calculate the total number of humans that will be born after TI. Then i can calculate when TI would be such that the number of people born before or after me is equal!! Thus I would have an expected value for TI.