I really enjoyed it, though I had trouble figuring out what to combine at times. I thought I was on to something with scientist + fire, and it took me ages to get to that situation due to the decay mechanic, but nothing happened. I was thinking at first, perhaps the fire decays before the game checks if two objects can be combined, but I found out that, no, fire + scientist does nothing.
I Think it could be improved by having a grid system, Another one of my concerns was that maybe the fire + scientist just didn't detect each other? I had a few moments where the monkey + brain didn't work, but I was able to fix it my moving them around slightly. By placing things somewhere in a grid, that would remove the concerns that two objects aren't colliding. Just place them in the same square.
In the end, I got to the lump of gold? I think that's what the object was- I didn't check the journal and it decayed before I was able to figure out what to do with it. Really cool game though! Nice work.