The phrase "earliest predecessor" refers to the person or thing that came before all others. It signifies the very first or earliest version or ancestor of something. Full definition
Two years earlier the predecessor school on the site had been graded outstanding. (bbc.co.uk)
Australia became Toyota's first export market after early predecessors of LandCruiser 70 Series — the FJ25, FJ45 and FJ43 — were employed by construction magnate Leslie (later Sir Leslie) Thiess during the construction of the Snowy Mountains Hydro Electric Scheme. (motoring.com.au)
The steel club's earliest predecessor from a fitness perspective would be the meel. (onnit.com)