How was the resemblance between apes and humans explained in pre-Darwinian biology?
The time before Darwinism, people believed life as an entity which is created rather evolved. But there were great biologists interested in the relationship between species, who deliberately thought of evolution ideas and some of them believed in ape-human similarities and placed humans and apes in same group. 



In 1699, Edward Tyson, an English anatomist, dissected an ape specimen(chimpanzee) and showed that its anatomy closely approaches ours.But he didn't established any relationships between humans and apes. It was first done in 1738 by Swedish scientist  Linnaeus in his book Systema Naturae .After that in 1759, Lamarck, a French naturalist  who was Darwin's predecessor in general theory of evolution, stated that humans were derived from up-right walking apes.


  In 1759, just half a century before Darwin was born and precisely one hundred years before he published his famous book , "Origin of Species", Linnaeus, the great Swedish scientist, discovered that man was a mammal. He then placed man in the Order of primates, which means literary the first, or the highest,order of mammals.It comprises all the monkey like forms, including the man-like apes.
  Reference




References

Primate Evolution and Human Origins - Russel L. Ciochon &amp; John G.Fleagle

Human Evolution: A Guide to the Debates - Brian Regal