An adverb 'So' vs a conjunction 'So'

This novel is set in a Chinese village before World War One.
The protagonist Wang Lung and his wife are working on their wheat field.

The earth lay rich and dark, and fell apart lightly under the points of their hoes. Sometimes they turned up a bit of brick, a splinter of wood. It was nothing. Some time, in same age, bodies of men and women had been buried there, houses had stood there, had fallen, and gone back into the earth. So would also their house, some time, return into the earth, their bodies also.
<The Good Earth by Pearl S. Buck>
I'd like to know if "so" is a conjunction, not an adverb.
Thank you in advance for your help.