There is some good evidence that children whose first language is tonal (e.g. chinese) develop perfect pitch at much higher rates than those whose is not (e.g.

There is some good evidence that children whose first language is tonal (e.g. chinese) develop perfect pitch at much higher rates than those whose is not (e.g. english). This strongly suggests that at least if you catch it at the right developmental stage, it is learnable. I haven't seen anything equivalent for learning later in life though, although ear-training exercises clearly make your estimation better if you are disciplined about it, but that is relative, not absolute.