That's the parent posters point. There's no such thing as "evolutionary psychologists". At least so far as academics within psychology and neurology recognize it.
You can dismiss evolutionary psychology as irrelevant to other social or neurological cognitive sciences (which I would argue is also wrong), but it doesn't mean interesting and useful research is not being done.
How does a psychologist do anything like this? Mental processes of living things and how those respond to environment can be observed. How can mental processes of millennia ago be observed?