What's the best estimate one can make about the average lifespan of a new population?


For instance, let's say an alien kind of life came to earth and we're able to breed then. We then get 1000 aliens and start analyzing them.


Assuming they can't breed on their own, let's say I start taking notes on their death. Maybe it's something like that:



```
1 year - total 100 deaths
2 year - total 300 deaths
3 year - total 600 deaths

```

My problem is that I only know the average lifespan of those who died. Who knows if 10% of this specie has a gene that makes them live for 100 years, while all the others usually die in less than 5 years?


So, considering I don't know how likely this would be, the best estimate I can do is assuming it's a normal distribution and going from there?



How to calculate average lifespan of a new population?
You should modify the diff eq for population growth: dN/dt = (b0 - d0) / N0. Changes in a population over N time t, which is expressed as a ration of deaths subtracted from births over the population density at that time t.


Since you want to create another factor based on a different genotype, I'd suggest having a variable L that is a matrix for which genotype the species is. Or you could determine some kind of probability matrix which will establish the best estimate for one species to have the gene. Are you also considered the event of a species mutating or adaptation between gentoypes?


