How is there no limit to a human lifespan again?
You're probably reading about the recently-published responses to a publication that argued there is a limit to human lifespan.  

The original article is Evidence for a limit to human lifespan, and in the June 29 issue of Nature there are five responses to it:


Contesting the evidence for limited human lifespan
Many possible maximum lifespan trajectories
Is there evidence for a limit to human lifespan?
Questionable evidence for a limit to human lifespan
Maximum human lifespan may increase to 125 years


Each of these responses has, in turn, a reply from the original authors.

The arguments turn on fairly intricate details of statistical analysis and database interpretation, and I think it's fair to say that outside experts remain unconvinced either way -- neither the original article, nor any of the five responses, nor any of the five responses to the responses, presents a slam-dunk case for or against a limit to human lifespan.