In The Language Myth Vyvyan Evans presents the proposal that human language is a species of communication technology like writing systems, telephones, or computer networks. Just as we have no innate capacity for reading/writing, dialling phones, or clicking on links, we have no innate capacity for language. Instead, we humans were endowed with increased general cognitive ability, which allowed us to iteratively develop language, writing, telephony and computer networks. We know from archaeology, historical records and our own memories that communication technologies such as writing systems, telephony, and networked computing (along with a host of non-communication technologies) have undergone periods of exponential improvement. Science, philosophy, and math has shown in some cases that certain technologies (e.g., computer programming languages) have advanced to their logical or physical limits, or in other cases (e.g., Audio encoding) have advanced to the limits of human cognition.
This proposal makes a prediction about language. Either it is still advancing, it has reached its logical limits, or it is at the limits of human cognition. The second option has been shown to be false as there are classes of language which are more expressive than human language. The first and third, however, are viable hypotheses. The first hypothesis, that language continues to improve like, say, photovoltaic cells, seems like it would be quite demonstrable if it were true. Since we have known for centuries that the language spoken by a given generation varies, albeit slightly, from that of the previous generation, a scientist seeking to provide evidence for the first hypothesis would only have to demonstrate a general trend of improvement in a language across generations. I know of no studies that provide such a demonstration. This leaves the third hypothesis: that language has developed to the limit of human cognition. Notice that the third hypothesis is the UG hypothesis: that humans are born with an innate capacity for language. Absent any evidence of language improvement, Evans' proposal is the UG hypothesis.