A proper calculation using Bayes' theorem is missing in the article. The conclusion is false.
E.g. let's assume that (2) and (3) are false. So, we know with almost 100% certainty that we are not living in a simulation, and we know with almost 100% certainty that a posthuman civilization is going to run significant number of simulations of their evolutionary history. Concluding that (1) must be true is thus precisely the Doomsday argument which is false because of improper Bayesian reasoning: The principle of indifference is used while the self indicating assumption is rejected. This is a logical inconsistency which leads to erroneous conclusions. Saibal Nick Bostrom wrote: ``I have just finished a paper (which had been existing in a half-baked form for much too long) that might be of interest to the list members. It has its own website at http://www.simulation-argument.com (which also contains a few related resources). Are You Living In a Computer Simulation? Nick Bostrom (2001) ABSTRACT. This paper argues that at least one of the following propositions is true: (1) the human species is very likely to go extinct before reaching a "posthuman" stage; (2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof); (3) we are almost certainly living in a computer simulation. It follows that the transhumanist dogma that there is a significant chance that we will one day become posthumans who run ancestor-simulations is false, unless we are currently living in a simulation. A number of other consequences of this result are also discussed.´´