Wonder Woman's Amazons and Themyscira is probably one of the trickiest places for world-building that I can think of. A number of different factors come together and intersect with each other, and there are a lot of different moving and interlocking parts to decide upon, all of which have different implications for Wonder Woman's construction, ideological implications, and follow-on effects.
The five axioms I am using here are the following:
- The Amazons are competent and a positive force of civilisation.
- The Amazons went into seclusion on Themyscira circa 3,000 years or more ago.
- Diana does not have a biological father.
- Diana enters Man's World in roughly modern times (where modern times is defined as the First World War forward).
- Diana isn't 3,000 years old.
Those five axioms are then combined with various world-building choices, and I will try to look at what the implications then will be, for Diana and Themyscira. I'm sure there are other ways to fulfill these (or similar) axioms, but so far these are the three I have come up with, and their follow-on effects on Themyscira and narrative.
(1) Prophesised Clay
This is basically the Marston and Pérez take: Hippolyta longs for a child, sculpts one from clay, and Diana is brought to life by some or all of the Olympic goddesses.
One assumption here is that the gods are rather active in Diana's life from the very start. But to me a big question is why Diana was born when she was, because it needed the active decision of Aphrodite (or some other of the goddesses), and then you run into the problem of prophesies, since Diana is supposed to be ready for action when Steve arrives.
One way to handle that could be to have the goddesses deciding to act when they feel Krypton exploding or Superman arriving in the solar system. That would make Diana roughly the same age as Superman, and having her as a reaction to Superman sort of fits with out-of-universe reasons for creating Wonder Woman, but I think seconding Wonder Woman to Superman in-universe is a bit troubling, so if anyone has a better reason, I'd be happy to hear about it.
Since the Amazons have been around for a long time, one can easily justify scientifically advanced Amazons, but at the same time you need to keep track of a big miracle in recent times. That points towards Amazons heavy on magitech or similar.
(2) Kid Amazons
This was an early idea of mine. As the Amazons went into seclusion, some of them were pregnant or were caring for children (both girls and boys). The girls went into seclusion too, and the boys were left in the caring of the gods (Artemis and Hermes make the most sense). Hippolyta possibly had to give up her son during this, and the grief over that led her sculpt Diana from clay, after which Diana was brought to life as above.
There are some potential upsides with this take. It gives Diana other kids to grow up with, only slightly older than she is. It gives Diana an older half-brother somewhere in Man's World. It gives a clear explanation for why only certain Amazons could compete in the games in order to leave with Steve for Man's World—they are the children of the original Amazons, who swore to never leave.
There are also some issues with this. A 3,000-year-old Diana can be a hard sell.
This can be solved through some form of time dilation—that time runs differently and much slower on Themyscira, at least for much of its history. For the Amazons, only 20–25 years have passed since they arrived, though for practical narrative purposes it might be good that the time dilation is no longer in effect after Steve ended up on the island. This solution will pretty much require high-mythical Amazons, rather close to their Bronze Age roots. Rucka's Rebirth Amazons probably come rather close to this.
However, one also needs some narratively plausible explanation for why Diana's half-brother is out there to meet her, when he supposedly arrived in Man's World as an infant. Messing with time carries with it narrative complications and indications of specialness that I'd prefer to avoid.
(3) Reproductive Science
This is inspired by the possibility of taking an egg and using it to fertilise another egg, in this case eggs probably provided by Philippus (who provides the egg that is turned into a sperm-equivalent) and Hippolyta. Here we are firmly in science fiction territory, though definitely within the realms of plausibility.
An upside for this is that we can easily skip messing with time or with recent divine interventions. The Amazons didn't develop the science needed until about 20–40 years before current time. It also gives them a clear case where they have superior science and technology to the modern world, so is well suited for technologically advanced Amazons.
This version leaves relatively little room for actions from the goddesses on the Amazons, and thus make it tricky to give Diana her full set of powers. It will also require some way to involve and manage any other daughters the Amazons create using this method, after Diana is born.