An element of my worldbuilding project involves a highly advanced prehistoric human civilization with space flight capabilities and relatively extensive interplanetary colonization. In my setting, this civilization was destroyed approximately 200,000 to 100,000 years ago by runaway self-replicating weapons, leaving no obvious traces behind. The war left only a tiny fraction of humans on Earth alive and all replicators permanently disabled through a final cyber-attack.
Would it be plausible for this to happen while leaving very little evidence (as in easily suppressible evidence, at least on Earth)? If not, what mechanisms would allow such an erasure?
Replicators are thoroughly space-flight capable from having several interplanetary ship designs built into them. Similarly, the replicators are capable of forming a full combined-arms force with infantry, armor, artillery, naval and aerospace components.
Raw material processing is mostly done the traditional way by mining, scavenging or chemical synthesis. However, externally powered nanoswarms makes material processing and manufacturing very, very quickly. Think RTS games, but with actually reasonable timescales (hours and days instead of seconds and minutes). Materials used by the replicators are generally steel or titanium alloys blended with ceramics, and non-biodegradable plastic.
Final cyber-offensive was conducted by sending well-engineered malware through the linked computational nodes that communicates through hand-waved FTL channels, so spread is nearly instantaneous. The malware issues repeated data access requests, much like self-destruct features on flashdrives, which causes physical damage to many circuits. It will also brick the firmware of the low-level controllers, just to make sure. Without the computing hardware, the replicators will fall silent, or maybe fail catastrophically, and let weathering, however applicable, take over.
The last humans were still alive because the replicators haven't finished killing all humans when their firmware got bricked and SSDs burnt out. However, most of the political and military personnel were killed during the fighting, and the few surviving scientists/engineers who launched the malware have demonstrated deficiencies in managing an entire society, so social collapse happens a few decades after the end.
Overall Colonization Scale
Large Lunar and Martian cities exist, along with orbital elevators over Earth, Luna, and Mars. No attempts at terraforming Mars were made. A few small Hermean solar observatories are the only manned sites sunwards from Earth. The asteroid belt is sparsely colonized with small mining stations, which are mostly automated and hold little personnel.
Smaller cities exist on the Jovian Moons, mostly pioneers and the occasional penal colony or government black project. No permanent habitations exist beyond the Jovian orbit, except for a single research center in Neptunian orbit, where the von Neumann weapons first broke free.