Altair is one of two worlds created from the dividing of the Earth after the events from Genesis of Aquarion 12,000 years ago.
According to The Book of Twin Stars, Altair and Vega was once the planet Earth. However, due to the Tree of Life having withered away, mainly from desecration by Toma's twisted love for Apollonius, the Earth eventually grew fragile and reached a point in which it split in two.
In recent years on Altair, the human populace was exposed to 'The Curse of Eve'. This curse has caused females (born on Altair or abducted from Vega) to either succumb to death or turn into males. Females with high elemental powers has shown to resist this curse but it eventually starts to change their personalities and eventually their own bodies into those of men. As such, the entire populace is male.