Fridge / The Water Horse: Legend of the Deep

• Darwin would have a Flat "What" moment if you told him about a species where each specimen produces only a single child and then immediately dies, considering that it'd take them millions of years to evolve this trait (and that's not even getting into the difficulty of imagining an environmental situation where this would be anything but detrimental), and there are a lot of things that can either kill an organism before it reaches reproductive age or just prevent it from being able to reproduce in the first place: disease, injury, predation, toxins, birth defect, infertility, etc. So how has this species managed to survive for so long without encountering any of these factors?
  • Magic.
  • Additionally, we are never told if the water horse species always worked like this or not. If they are a purely biological animal, with no supernatural aspects at all, there would have been more of them at one point. Numerous species are able to asexually reproduce when deprived of a mate. Perhaps by the relatively modern times, the species had been so drastically reduced as what was once a population is now reduced to a single individual.

• For that matter, why is there still only one? Shouldn't a set of identical twins have occurred at some point?
  • Magic.