Linguistics is about understanding what languages are like and why they are like that. The study of language evolution is concerned with the second of these questions in particular. Given the special nature of language in the animal kingdom and the fact that language fails to fossilize, this is not straightforward. In fact it has been termed the hardest problem in science! That's probably a little hyperbolic. There are almost certainly questions in science that are entirely beyond empirical investigation, but language evolution is not one of them. In fact there are a number of empirical avenues available, including comparative biology, genetics, complexity theory, mathematical and agent-based modeling, laboratory experiments, and statistical analysis of corpora.
Penn has an unusually rich environment for study in this area. It brings together a number of resources and faculty who employ these approaches, as well as a deep fund of expertise in the study of language and evolution, both biological and cultural. Language evolution is a highly interdisciplinary field, and Penn is a place where interdisciplinary work is actively encouraged and easy to achieve.
You could join us.