What source type fits this quotation Chewing licking and sucking are extremely widespread mammalian activities which in terms of casual observation have obvious similarities with speech?

Here's why:

* Specific Terminology: The use of terms like "mammalian activities" and "casual observation" suggests a scientific approach to understanding the subject matter.

* Comparative Analysis: The phrase "obvious similarities with speech" hints at a comparative analysis, which is common in scientific research.

* Formal Tone: The overall tone of the quotation is formal and objective, characteristic of academic writing.

It's possible the quote comes from a study on animal communication, developmental psychology, or even linguistics, as these fields often explore the connections between physical actions and communication.

To pinpoint the exact source, you'd need more context, such as the name of the author, the publication title, or the year of publication.