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:
Specific studies of Slavic genetics followed. In 2007 Rębała and colleagues studied several Slavic populations with the aim of localizing the Proto-Slavic homeland. The significant findings of this study are that:

Question:
When did Rębała and colleagues studied several Slavic populations with the aim of localizing the Proto-Slavic homeland?

2007