Based on the common tradition narrated from Imam Muhammad al-Baqir (a.s.), when asked about the meaning of Surah Qaaf, verse, 15, he (a.s.) replied that there were Adams before and there will be Adams after. However, we do not have any further information beyond this. Nothing has been said in description of them.
The Almighty says in the Holy Quran:
وَيَخْلُقُ مَا لَا تَعْلَمُونَ
"And He creates what you do not know." (Surah al-Nahl, verse 8).
And Allah knows best.