I cannot create a summary of this article because its content is not available in the search results provided. Although the article is from the January 2026 issue of Science titled "A new cell type drove human brain complexity", the specific text and details of the study are not in my sources. The results provided contain information about other discoveries related to the brain - such as the formation of new cells in adulthood, mapping the mammalian brain, or the development of the human brain - but not about the specific article you asked to summarize. If you have access to the full text of the article, I can help you create a summary based on its content.