The Elders is a particularly vague part in the plot. The Martians left behind underground settlements on Mars, discovered by human
around 2075. Miriam Bancroft displays one fossilized relic of them, at some point. They were a tall race, insect like with wings capable
of flight, living in towers with small cavelike habitats. The main innovation humans got from the Bradbury site were star charts
pointing us to inhabitable worlds in other star systems, jump starting our expansion by centuries. For centuries, intact Martian bodies
were never found, and their biology was significantly different from ours.
The development of the cortical stack was not directly aided by discoveries from the Martian race. Nor the digital human freight.
That particular piece of technology came from old fashioned human ingenuity. It was well underway by the time the martian ruins were discovered.
The martians have a bit more of a role in the second and third books of the trilogy, but they're still little more than a story backdrop.
We learn that they still have working technology out there which has been functioning on a seemingly endless loop for half a million years.
We learn that they could essentially bend the geometry of space-time. We learned that they had faster-than-light weaponry that
we can't even begin to understand. We eventually learn that they could vaporize an object as complex as an organic being,
completely scan it down to a subatomic level and recreate it digitally. But anything beyond that is mere speculation,
even after centuries of study.
The books emphasize that in the 400 or so years since Martian artifacts were discovered, humanity has been able to learn
next to nothing about them. They're simply too advanced and, well ... Alien. Virtually nothing is known about their society, technology,
what they were doing or where the hell they disappeared to. The only particularly useful thing that humanity was able to learn from
martian ruins was the location of nearly every habitable biosphere within hundreds of light years, giving them dozens of colonization targets
with that were guaranteed to be able to support human life. That's what jump-started the era of human expansion into the galaxy.