This question raises a number of points; there is a difference between what the professor is quoted as saying, what he actually meant and what may be inferred. This then leads to a fuller assessment of the use of 'obviously, clearly, evidently, apparently' in this context.
The findings by the professor are not guaranteed to be repeated everywhere and with everyone. Therefore he can only make a claim against the number of people involved. But even here there must be some doubt if only because we do not know what questions he asked (without going through his research papers) and this makes a clear answer difficult.
He may say obviously because it is obvious to him as he assesses the results but it is not obvious to us.
Clearly is almost the same as obviously but not as strong.
Evidently is very strong as that implies he has been able to use scientific analysis which should stand up to rigorous challenge.
That leaves us with apparently which IMO is the correct answer. It can only be apparent because it cannot, as yet, be verified.