I have to disagree that I/we/they have any moral obligation to perpetuate the species.
Have we been directing evolution for eons - abso-phucking-lutely. Both inadvertantly and overtly. Look at all the breeds of dogs - all from humans selectively breeding dogs to fill a role in our lives.
It's hard to "prove" that we have a moral obligation to do so, but when we break it down to a moral obligation being doing right vs doing wrong, it has a ripple effect. Doing right is feeding children properly, keeping them safe, educating them, etc. By default, this helps keep the species going, and makes it stronger (or at least longer-lasting, as we have weakened ourselves in some ways).
The most basic reason for the existense of an organism is to reproduce. If we do what is "right" (our "moral obligation"), we reproduce. In some cases it probably should be a moral obligation NOT to, but those are the outliers.
By doing right we may not be TRYING to keep the species going, but it sure is a natural byproduct of other actions.