The place for the oldest proof of fire and use of obsidian, an volcanic sediment is near the oldest know continue habitat of hominid since also 1.9 million year, the Melka Kunture.
https://t.co/GBjL0gR5Ip
It should be no surprise both technology's and first permanent habitat in Ethiopia is a hotspot for volcano's.
And it's my belief the mastering of fire is not due to an natural phenomena as a periodic lighting, if we look at the migration path of those hominid they follow the volcano's out of Africa, as we can see in Saudi-Arabia.
Their technological advance in stone-technique based on a volcanic stone forced them near the fire of it, got used to it, observed it's property and applied it to better their own living conditions, probably already started with the homo habilis which effected their offspring.
Since then human brain volume evolves gradually, this if we ignore Homo Naledi and Homo Floresiensis which are both dwarf hominid.
https://t.co/zg8FWNApCS