There are two sentences:
In artifacts from as early as the Stone Age, mathematics and art can be seen to have fused in the geometric patterns which decorate pottery and carpentry.
In artifacts from as early as the Stone Age, mathematics and art can be seen to have fused in the geometric patterns to decorate pottery and carpentry.
I think the first one is the most suitable option for this sentence, but someone has another idea as option 2 noted above. I'm a bit confused. Hope someone could help.