Prior to the current civilized era, leaving the Earth gravity well was exceedingly expensive.
Only a small number of humans did so over time. As industry and biospheres where built off-planet, exponential growth kicked in, and humans born from colonists started outgrowing the colonists.
The colonists where Earth's best and brightest, and they had to survive through a crucible of the harshest environments humankind has ever lived through. Initial generations faced an overall negative growth rate, where only the smartest, toughest, and most resourceful survived. Those that did survive gave birth to dynasties which stride the stars.
The Starborn are the inheritors of the Universe. They are the World Forgers.
All the while, Earth wallowed in its muck. Unable to escape the heat-trap, it remained stuck below a Type 1 civilization while the Starborn had no practical environmental limit before Type 2.
Trade of goods wasn't practical due to the gravitational barrier, and Earth lost interest in the off-world colonies and focused on its own problems. The Starborn colonies either died, remained dependent on Earth and hence tiny, or became self suffient and grew exponentially. Within a few generations, the commanding heights of Starborn civilization had gone its separate way from Earth. It never really looked back.
Starting a few 100 years ago, it became practical to mass-lift the Earthborn up to space. But it wasn't anything the Earthborn could afford (the value of anything physical on Earth was still exceeded the lift costs, and Starborn really wasn't interested in backward Earth technology. Some enjoyed their primitive low art, but that isn't enough for real trade.) Still, as a charity project, a Beanstalks was built (and it was used to build more), and Earthborn where lifted off planet. 121
Poor, with little education and knowledge and contacts, they grew in number.
Meanwhile, the Starborn proceeded towards a Type 2 civiliation. Dismantling planets for raw materials to build worlds and energy gathering mechanisms to enable interstellar travel. By Type 1.4, (roughly 10 million times richer than the USA) lifting a few billion tonnes of flesh off Earth becomes an easy problem. But what will we do with them?
After the beanstalk was built, the Starborn referred to the new wave of colonists as Earthborn. Their descendents are still called that, as are this new wave of flesh enabled by modern lift technology.
The Starborn are the descendents of the first wave(s) of colonization. It is their civilization that is a Type 1.4 civilization (1 part in 1E6 of the Sun's energy captured); the Earth-bound civilization is Type 0.8 (heat and ecosystem constrained), while the Earthborn in space civilization is barely over Type 1.
Technologically and wealth-wise, the Earthborn civilization is to the Starborn as an uncontacted tribe today is to the USA. And the actual planet-bound civilization on the planet is half again poorer.
Everyone believes that the Earthborn have the potential, given a few 100 years, to reach biological maturity in space. I mean, the Starborn started off as Earthborn! A few dozen generations of gene optimization, education, gestalt uploads and integration would bring them up to civilized human (aka Starborn) standards. Meanwhile, the Starborn permit the Earthborn to join them on some exploration. It would be cruel to leave them trapped down there. And their culture is so interesting and cute. 335