Whether it was or wasn’t can be disputed but it is possible.
(6) A test can be made from genome-wide estimates of the time to the most recent four lineages (TMR4L)
Building on Joe Felsenstein’s comment “it would be even better to find more polymorphisms involving multiple haplotypes and put all that information together”, Joshua Swamidass has done a preliminary analysis in which he sought to examine genome-wide patterns of multiple haplotypes and put them all together to examine whether or not a bottleneck of two is plausible in the human lineage in the last few million years. He did this by estimating the time to the most recent four lineages for each recombination block in the autosomal genome (unlike mitochondrial genomes and Y chromosomes, four gene lineages can pass through a bottleneck of two within autosomes). More detail can be found here. In brief, this analysis suggested that a two-person bottleneck is plausible over approximately 500,000 years ago. Again, this is a preliminary analysis, and could be developed further with more accurate phylogeny building, and more sophisticated statistical approaches. I think that Swamidass intends to work this up for a publication. (emphasis mine) Adam and Eve: lessons learned by Richard Buggs.
I disagree with the time scale.