<Snipped quote by Apollo26>
Uhm, from the looks of things - probably everything. Imagine everyone's starting off sometime during the tribal-age, where animal husbandry isn't a -thing- yet, nor agriculture. Heck most of us haven't even went into bronze age yet lol. Considering the speed of advancements of your race to have had pulleys and compound bows - they'd have spaceships in the next 100 years XD
I concur with the above statement.
Since the Katyushas never met anyone, we can simply pretend they never existed. Simplest way to go about it. There were only 12 Yelb if I remember correctly, so they could have been killed by a pack of wild animals or anything like that.