You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Slavs

Context:
Proto-Slavic, the supposed ancestor language of all Slavic languages, is a descendant of common Proto-Indo-European, via a Balto-Slavic stage in which it developed numerous lexical and morphophonological isoglosses with the Baltic languages. In the framework of the Kurgan hypothesis, "the Indo-Europeans who remained after the migrations [from the steppe] became speakers of Balto-Slavic".

Question:
Proto-Slavic developed numerous lexical and morphophonological isoglosses with what languages?

Baltic languages