1. What are two of the major challenges associated with studying ancient DNA?

2. Provide two key insights into the evolutionary history of Neandertals that have been derived from the analysis of mitochondrial DNA (mtDNA). In what ways might the use of mtDNA be misleading or limiting?

3. Who were the Denisovans? From an anthropological prospective, what is remarkable about their discovery?

4. Based on the recent publication of the Neandertal and Denisova genomes, describe the current model for putative hybridization and gene flow between these lineages and modern humans. Include in your answer the historical time, approximate geographic location of inferred hybridization events and the genomic extent of introgression.